40 V8 compression change all cylinders same time

[L78CHEVELLE]

I have a original 1940 85HP engine that has been rebuilt professionally about 3 years ago. The engine ran great for the first year and half for about 2,000 miles. Compression on each cylinder was 100 to 105. Now the engine runs poorly, misses, hard to start when hot, and is not reliable. I checked the compression today and every cylinder is 60 to 65 pounds. Valve adjustments are good. I am confused and discouraged. Can any one give me some options?

[Fordestes]

Check for a plugged exhaust, bad timing gear. cam gear may have lost a tooth, some gears were made of a phenolic material .

[WABOOM]

Watching this thread out of curiosity.

[Tinker]

Engines need to be run. Hot Hard to start is a coil indicator, for starts.

[Tinker]

not sure how relative upper engine lucubration is. L heads rely on it. Lead gas reason.

[flatheadmurre]

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Was it sitting for a long time before this happened ??
Since it was rebuilt and i assume no taper in cylinders...rings may just be stuck.
You favourite penetrating oil down the cylinders...then run it up to working temp...see if it improves.
Or long periods of idling...having given you ring to wall sealing issues.
Over rich carburation also has this effect.

[Ol' Ron]

Was the throttles wide open during tests. Screw driver works well.

[Kurt in NJ]

Power valve?? running very rich, gasoline washing cylinder walls reducing compression??, does the oil smell like gasoline??

[joe 1950]

don’t no what grade fuel your using but i’m sure the rebuilder would have put the hardened seats in ,don’t use any fuel that has corn in it ,these old girls fuel systems just don’t like it something to try ,add the proper amount of marvel mystery oil to the gas and oil and drive it ,these old flatheads always had problems with valves sticking just enough to lower compression witch will cause hard starting it may take a while but it’s easier than throwing a bunch of parts at it and still have the same problem ,i’ve used mmo in my model a and my 50 cpe with great results keep us informed

[deuce_roadster]

How often have you retorqued the heads? If aluminum heads, I have to do this at least 4 or 5 times before they stop moving. Alum heads torque stone cold, cast iron torque hot.

[Flathead Fever]

Like Ron said, You need to hold the throttle wide open when doing a compression test. Otherwise the cylinder will not fill with enough air to get an accurate test. You should have a battery charger on the battery so each cylinder is checked with a full charge on the battery. You should pull all the plugs so the engine can crank faster. That's officially how its done. I've done it without doing any of that stuff and have gotten good readings but since your readings are bad you probably should perform the test correctly.

If this was a quality rebuild, its unlikely all the cylinders have poor compression after only 2000 miles. I try a different compression gauge just to verify yours is accurate. You can have a faulty compression gauge and the problem could be elsewhere.

The first thing would be to give each cylinder a squirt oil and see if the compression comes up. The oil gives the rings a temporary seal. If the rings are bad the compression will come right up to specs with a squirt of oil. If you got the engine hot the rings could have lost their tension.

If one cylinder was low you would look for a valve problem, worm cam lobe, broken ring, blown head gasket on that one cylinder. But when all cylinders are low you look for something common to all of the cylinders. If it had a timing chain, it could be stretched. But with gears its unlikely it jumped a tooth. It would probably strip a tooth off and then not run at all. If you had timing marks on the crankshaft pulley you could check it to see if the timing had changed do to the gears not being aligned properly. Always make timing marks and a pointer on your flatheads when you have the heads off!

A plugged exhaust can be checked with a vacuum gauge. I've mostly seen it happen with melted catalytic converters. It happens a lot on those cars. But mufflers can have baffles break loose and then cover the outlet hole. Usually you will hear a rattling muffler. It acts like a governor and will only let you go a few mph but it doesn't run bad it just will only go so fast and it cause the engine to run hot. I suppose a rodent could build a nest inside the pipe or you could run over something and collapse the pipe. You could try separating the muffler from the inlet pipe and see if it makes any difference. You could also do a compression test with the muffler disconnected. I think thins is unlikely your problem, it's pretty rare, at least here in SoCal. Here is a video showing you home to check it with a vacuum gauge. They are neat tools, everybody working on cars should have one.

https://www.ericthecarguy.com/faq/so...t-restrictions

You can also take a rubber tipped air nozzle and with the piston at TDC blow air into the cylinder and see where it comes out. If it comes out the intake the intake valve is burned. Out the exhaust, the exhaust valve is burned. Out the radiator you have a crack or bad head gasket. Out the oil fill the rings are worn. Some air will normally get by the rings. The only way to accurately test them is with a special tool that measures the percentage of leakage. Without that tool about all you get check is for a major failure like a hole in a piston.

[L78CHEVELLE]

Did the first compression check with the engine complete together just like I pulled it in the garage with all the spark plugs out. Got 60 to 65 on each cylinder. Took the intake off and checked the compression again on each cylinder. Same results of 60 to 65 on each cylinder. I am going to try another gauge tomorrow. When I had the engine rebuilt it had only 26,000 original miles and had the sleeves in each cylinder. The machine shop took the sleeves out and put in Ford 8BA standard pistons telling me that was the normal thing to do. Like I said it ran good for 2,000 miles after that.

[Craig CT]

Originally Posted by L78CHEVELLE

I have a original 1940 85HP engine that has been rebuilt professionally about 3 years ago. The engine ran great for the first year and half for about 2,000 miles. Compression on each cylinder was 100 to 105. Now the engine runs poorly, misses, hard to start when hot, and is not reliable. I checked the compression today and every cylinder is 60 to 65 pounds. Valve adjustments are good. I am confused and discouraged. Can any one give me some options?

Hi L78CHEVELLE; It could be your cam timing. Good luck, Craig.

[Kruzn40]

Do a leak-down test on each cylinder with compressed air. That will give you an idea of the path that your cylinder pressure is using to make its escape.

[BUBBAS IGNITION]

Cam , cam gear issue is the only issue that would lower compression on all cylinders. I would look for a messed up worn cam gear.......

[Craig CT]

Originally Posted by BUBBAS IGNITION

Cam , cam gear issue is the only issue that would lower compression on all cylinders. I would look for a messed up worn cam gear.......

Hi Bubba; If it's a press on it probably just moved a little, Craig.

[L78CHEVELLE]

Tried another compression gauge and put some oil in the cylinders with the same results of 60 to 65 in each cylinder. Checked the exhaust today to see if anything was plugged. Everyone may laugh at my method for check the exhaust system. I put a shop vacuum hose in the tail pipe and made it good and tight. The shop vacuum pulled good air from the front of the engine with the intake off and me turning the engine over with the starter. Next step is to take out the radiator, fan, crank pulley, distributor, front engine cover and see what I find. I can find no one local to help me with this deal and have become very discouraged. Thanks to all on the Ford Barn for giving me ideas of how to correct this problem. New rebuilt engine with a compression problem has taken the wind out of my sails. Will post what I find when I take off the front engine cover if I can figure out what I am looking at. Should there be a dot on the cam gear and a dot on the crank that line up together if correctly installed?

[Fordestes]

Sounds like you are headed in the right direction, the cam gear and crank gear have a mark on each and should match together , is it possible the builder re used the old cam gear ,as you stated it was a low mileage engine to start with , this has happened ,when a part looked good sometimes it gets re installed, someone not knowing the habits of a fiber gear may have assumed it would be ok to re use?

[BUBBAS IGNITION]

Originally Posted by L78CHEVELLE

Tried another compression gauge and put some oil in the cylinders with the same results of 60 to 65 in each cylinder. Checked the exhaust today to see if anything was plugged. Everyone may laugh at my method for check the exhaust system. I put a shop vacuum hose in the tail pipe and made it good and tight. The shop vacuum pulled good air from the front of the engine with the intake off and me turning the engine over with the starter. Next step is to take out the radiator, fan, crank pulley, distributor, front engine cover and see what I find. I can find no one local to help me with this deal and have become very discouraged. Thanks to all on the Ford Barn for giving me ideas of how to correct this problem. New rebuilt engine with a compression problem has taken the wind out of my sails. Will post what I find when I take off the front engine cover if I can figure out what I am looking at. Should there be a dot on the cam gear and a dot on the crank that line up together if correctly installed?

Wouldnt worry so much in regards to the dots as i would TDC versus actual valve position....

[STEVE O]

Just wondering, being you have the intake off and put it on top dead center (not sure how to be sure it is exactly on TDC) exhaust stroke you should be able rock the crankshaft one way then the other and see the intake valve move one way and the exhaust the other way. If not something has slipped. If this is true on these flatheads of this era as later v8s that would check cam timing without pulling the timing cover????

[Craig CT]

Originally Posted by bubbas ignition

wouldnt worry so much in regards to the dots as i would tdc versus actual valve position....

x 2

[L78CHEVELLE]

Originally Posted by BUBBAS IGNITION

Wouldnt worry so much in regards to the dots as i would TDC versus actual valve position....

Wouldnt worry so much in regards to the dots as i would TDC versus actual valve position....
__________________
If it Makes Spark, we do it !!!!
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Can you give me some more details of how to determine TDC with the head on and what is the valve position when TDC is achieved? Can I put a long thin rod in the number one spark plug hole and determine when the piston is at top dead center? Should the dot on the cam gear and the dot on the gear on the crank line up on top dead center? If the dots do not line up at top dead center on number one piston then I know the cam gear has slipped? I have never rebuilt a flathead engine or set the timing marks before.

[Jack E/NJ]

https://www.jalopyjournal.com/forum/...caster.542626/


Jack E/NJ

[tubman]

"L78CHEVELLE"- Don't take this wrong, but you do understand the concept of a "press-on" cam gear, don't you? From your "handle", I think you might be familiar with only "bolt-on" cam gears. Early Ford V8's are different.

[STEVE O]

I personally have never installed the press on gear in the early flatheads (done plenty Cummins diesels with press on gears) but reading I see in one article that the cam and the gear have a mark to index the cam gear to cam and of course the 2 dots for the cam to crank gear. Since it ran good to begin with the dots must have been right but the possibility of the cam gear slipping on the cam could have happened. I wish I could say but I don't know on these era flatheads how to find TDC without a head off.

[Mart]

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Before you take anything else apart, it might be worthwhile just taking stock of what is going on.

You have the intake off.

Number one cylinder is right hand side, at the front. Use the cable tie method to locate top dead centre on the No1 piston.

Observe the valves on either no.1 or No.6 cylinder. They should both be open by the same (small) amount.

This would be an indication that the cam and crank are in the correct relationship.

Link to thread describing tdc finding: https://fordbarn.com/forum/showthread.php?t=110405

Mart.

[L78CHEVELLE]

Thanks to everyone that has responded to my request for help. I have printed off the responses and will study them and try to come up with a solution to my problem. I first need to find out what the problem is and then see what my ability is to correct the problem and go from there. I will up date the post as I catch up to the suggestions I have been given.

[L78CHEVELLE]

Took the front of the engine off today. My 40 has the late production engine with the bolt on camshaft gear. The mark on the camshaft does line up with the mark on the crankshaft gear. Now I am even more confused. Has the camshaft worn down in 2,000 miles? I did use the diesel oil with Zinc in it since the rebuild. I did pump one squirt of oil in a cylinder and turned it over. Still got the 65 compression reading. Amy one got any ideas?

[Craig CT]

Originally Posted by L78CHEVELLE

Took the front of the engine off today. My 40 has the late production engine with the bolt on camshaft gear. The mark on the camshaft does line up with the mark on the crankshaft gear. Now I am even more confused. Has the camshaft worn down in 2,000 miles? I did use the diesel oil with Zinc in it since the rebuild. I did pump one squirt of oil in a cylinder and turned it over. Still got the 65 compression reading. Amy one got any ideas?

Hi L78CHEVELLE; If it's a faulty compression gauge that will take you back to carburetor and or ignition, Craig.

[Tinker]

If it's a new rebuild I'd suggest running it. Breaking it in on the bench is less effect then underload. If you trust your builder.



Think there was a post earlier on finding tdc with the head in. No marker on a stock 40s motor. You can make one. Find the compression stroke on #1 (thumb over hole), then the Basic idea is a stop (like a zip tie end) that you put in the plug hole of the head/cylinder and then rotate it till it stops (mark it on the cam pully), then rotate it the opposite direction till it stops again and mark it. The distance between the two is a rough tdc. A couple times is best. Or even better is with the head off and a dead stop.


There are better methods here, if I look. One idea was a spark plug that was hollowed out and a bent rod was welded in that would impede the piston from completing a cycle.


Either of these methods must be done by hand cranking. Never with the starter motor.


If your cam is off, it'll be apparent with the crank indexed to timing. Valves lashing correct...


Here is a barn version of a index. I use a timing bolt that has a welded point. Post #8

https://www.fordbarn.com/forum/showt...8503&showall=1




Just for fun.... Stock cam? or a regrind?




.

[L78CHEVELLE]

Stock cam that is new. Everything in the engine is new except the crank which was like new. Engine ran as designed for about 2,000 miles after the rebuild. Compression change and poor performance started about 300 miles ago and now the engine is down to 65 on each cylinder and very hard to start when it warms up to operating temperature. Valve clearance is 11 intake and 14 exhaust. Can some one tell me from experience a similar situation and cure from back in the day? The car is useless the way it is. Do not want to put a modern drive train in an original low mileage car. This problem is something odd for sure.

[BUBBAS IGNITION]

Originally Posted by L78CHEVELLE

I have a original 1940 85HP engine that has been rebuilt professionally about 3 years ago. The engine ran great for the first year and half for about 2,000 miles. Compression on each cylinder was 100 to 105. Now the engine runs poorly, misses, hard to start when hot, and is not reliable. I checked the compression today and every cylinder is 60 to 65 pounds. Valve adjustments are good. I am confused and discouraged. Can any one give me some options?

Been a few days watching this thread and we all went for the low compression, cam shaft etc. Looks like all is fine there so far . Lets look at the miss fire issue for a minute ........

[Russ/40]

Forgive me for asking, but you say the valve lash is .011" intake and .014" exhaust. What procedure did you use to position the cam for the lash adjustment? Did you make a valve lash adjustment before this problem arose?

[L78CHEVELLE]

I have the problem with the low engine compression and checked the valve lash as a possible cause thinking with a new engine the adjustments could have changed during the break in. The new rebuild has the adjustable lifters. I checked the lash on each valve by opening the intake valve on each cylinder all the way open and checking the exhaust while the intake valve is at its peak opening. Then turn the exhaust valve on each cylinder to it's peak opening and checking the lash on the intake valve of that same cylinder. I think that would be a fool proof method. Is my thinking wrong on this method? The compression was 100 or more on each cylinder about a year ago when I checked it for peace of mind. Gradually the engine has run worse and worse. I am thinking maybe the new camshaft has been soft causing it to wear down and the valves are not opening enough. I thought the Shell Rotella oil would have prevented that. Got the camshaft from a well know supplier in southern Ohio.

[JSeery]

Originally Posted by L78CHEVELLE

I am thinking maybe the new camshaft has been soft causing it to wear down and the valves are not opening enough. I thought the Shell Rotella oil would have prevented that. Got the camshaft from a well know supplier in southern Ohio.

If the cam was that worn down the valve clearances would have opened up.

[flatjack9]

Originally Posted by L78CHEVELLE

I have the problem with the low engine compression and checked the valve lash as a possible cause thinking with a new engine the adjustments could have changed during the break in. The new rebuild has the adjustable lifters. I checked the lash on each valve by opening the intake valve on each cylinder all the way open and checking the exhaust while the intake valve is at its peak opening. Then turn the exhaust valve on each cylinder to it's peak opening and checking the lash on the intake valve of that same cylinder. I think that would be a fool proof method. Is my thinking wrong on this method? The compression was 100 or more on each cylinder about a year ago when I checked it for peace of mind. Gradually the engine has run worse and worse. I am thinking maybe the new camshaft has been soft causing it to wear down and the valves are not opening enough. I thought the Shell Rotella oil would have prevented that. Got the camshaft from a well know supplier in southern Ohio.

The proper way is to bring each valve to its peak and then rotate the engine one revolution and then check your clearance. A quicker way is to bring a piston to TDC on the firing cycle and check both intake and exhaust.

[Mike in AZ]

Re-torqued the heads? Any chance of posting pictures of front gears and engine? Mike

[Russ/40]

Originally Posted by L78CHEVELLE

I have the problem with the low engine compression and checked the valve lash as a possible cause thinking with a new engine the adjustments could have changed during the break in. The new rebuild has the adjustable lifters. I checked the lash on each valve by opening the intake valve on each cylinder all the way open and checking the exhaust while the intake valve is at its peak opening. Then turn the exhaust valve on each cylinder to it's peak opening and checking the lash on the intake valve of that same cylinder. I think that would be a fool proof method. Is my thinking wrong on this method? The compression was 100 or more on each cylinder about a year ago when I checked it for peace of mind. Gradually the engine has run worse and worse. I am thinking maybe the new camshaft has been soft causing it to wear down and the valves are not opening enough. I thought the Shell Rotella oil would have prevented that. Got the camshaft from a well know supplier in southern Ohio.

I'm thinking the valve lash is off. Bring each valve to max lift and rotate another full turn. Then adjust the lash.

[Tinker]

What is the cam? maybe I missed it, sorry

[JSeery]

And valve springs, are they higher than original spring pressure?

[L78CHEVELLE]

New stock camshaft purchased from well known southern Ohio supplier.

[L78CHEVELLE]

Ran good for 2,000 miles. All valve parts are new from well known southern Ohio supplier.

[L78CHEVELLE]

Originally Posted by JSeery

If the cam was that worn down the valve clearances would have opened up.

This is a good valid point I had not thought of. I can not figure out why the compression has dropped and engine is running and starting so poorly.

[L78CHEVELLE]

Originally Posted by Russ/40

I'm thinking the valve lash is off. Bring each valve to max lift and rotate another full turn. Then adjust the lash.

It ran good for 2,000 miles with the valve lash the same as it is now. Would that not eliminate the valve lash as the cause?

[Russ/40]

Originally Posted by L78CHEVELLE

It ran good for 2,000 miles with the valve lash the same as it is now. Would that not eliminate the valve lash as the cause?

Not if the degradation is due to burnt valves. Run them too tight and they will burn. Not having an engine open currently to check your adjustment technique, frankly I don't know if it is valid. I do know that is not going to put you directly on the heel of the cam. You mention your engine was built. When assembled, who adjusted the valves initially? Was it you with the method you have described?

[Russ/40]

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A gradual degradation of performance as a result of compression loss, to me anyway, screams burnt valves.

[L78CHEVELLE]

Originally Posted by Russ/40

Not if the degradation is due to burnt valves. Run them too tight and they will burn. Not having an engine open currently to check your adjustment technique, frankly I don't know if it is valid. I do know that is not going to put you directly on the heel of the cam. You mention your engine was built. When assembled, who adjusted the valves initially? Was it you with the method you have described?

The valves were adjusted by the machine shop. The valves would not all change at the same exact time resulting in the exact same drop from 100 to 65 in each cylinder of the engine. Only change I have made on the valve lash is to increase the exhaust valve lash from 12 to 14. We used the exhaust valve lash setting Ford gave in 1940 and then changed it to the new listing of 14 Ford came out with in 1947.

[L78CHEVELLE]

Originally Posted by Russ/40

A gradual degradation of performance as a result of compression loss, to me anyway, screams burnt valves.

Burnt valves could be the answer, but would all the cylinders react the exact same way going from 100 to 65 at the same exact time? I have only used straight gasoline in the car since the rebuild.

[L78CHEVELLE]

Originally Posted by Russ/40

A gradual degradation of performance as a result of compression loss, to me anyway, screams burnt valves.

I have the intake off now. This week if nothing new comes up I plan on taking one of the heads off and checking the valves to see if any show signs of damage. I have the tools needed to take the valves out.

[cas3]

before you take anything apart, do a cylinder leak test to see where the compression is going. if you dont have the fancy tool, i dont, you just weld an air fitting to an old spark plug, screw it in, get that cylinder to TDC and put low pressure, like 20lbs to it and listen. air out the carb=intake valve. air out the exhaust pipe=exhaust valve, and air out the oil fill/breather cap=rings. if you get all the same valves, i would suspect cam timing. this one is a puzzler!

[Tinker]

Originally Posted by L78CHEVELLE

Burnt valves could be the answer, but would all the cylinders react the exact same way going from 100 to 65 at the same exact time? I have only used straight gasoline in the car since the rebuild.

It would be very weird or highly coincidentally that every cylinder went from 100 to 65 in a yr. Might need to take the intake off.

[L78CHEVELLE]

Originally Posted by cas3

before you take anything apart, do a cylinder leak test to see where the compression is going. if you dont have the fancy tool, i dont, you just weld an air fitting to an old spark plug, screw it in, get that cylinder to TDC and put low pressure, like 20lbs to it and listen. air out the carb=intake valve. air out the exhaust pipe=exhaust valve, and air out the oil fill/breather cap=rings. if you get all the same valves, i would suspect cam timing. this one is a puzzler!

I am going to try and buy a piece that will allow me to put air into the cylinders to check for leaks before I take the heads off this week. If it was not for the help on the Ford Barn I would have to push the car to the back of the garage and wait until I came up with a new approach to the problem. THANKS TO EVERYONE.

[JSeery]

Leak down test sounds like a good idea to me.

[Russ/40]

I agree, the leakdown test is spot on. Wise move indeed.

[Craig CT]

[QUOTE=Craig CT;1746053]Hi L78CHEVELLE; If it's a faulty compression gauge that will take you back to carburetor and or ignition, Craig.
Hi L78CHEVELLE; I'd make sure it's not a faulty compression gauge before I took anything else apart. Good luck, Craig.

[Mike in AZ]

Post your procedure for compression testing when you try new compression gauge etc Something might be different which might give us a clue to why compression drop across all cylinders. Mike

[L78CHEVELLE]

Originally Posted by Mike in AZ

Post your procedure for compression testing when you try new compression gauge etc Something might be different which might give us a clue to why compression drop across all cylinders. Mike

I used another compression gauge and got the same readings on each cylinder. Will try the leak down with air on each cylinder as soon as I can get the tool. I will post the results.

[tubman]

I think everyone should be aware that the O/P said the engine started running poorly and when he checked the compression was down uniformly. I think that points to something more serious than bad testing technique or a bad compression gauge. The leakdown test sounds like the next best test.

[cas3]

i will mention this also, TDC on compression stroke, and if you are not right on top dead, some times the air will cause the crank to turn so keep your hands-fingers-trouble light cords-or cat away from the fan. good luck let us know what you find

[Mike in AZ]

Just curious about compression testing procedure. If throttle is not full open, will compression numbers be lower than at full open? Thanks. Mike

Never mind. OP is testing with intake off. CRAFT. Sigh. M

[deuce_roadster]

Any chance this engine got overheated and affected all the rings in a bad way?

[philipswanson]

Originally Posted by flatjack9

The proper way is to bring each valve to its peak and then rotate the engine one revolution and then check your clearance. A quicker way is to bring a piston to TDC on the firing cycle and check both intake and exhaust.

That's fine if you know where TDC is exactly but his method is probably much better if you don't.

[L78CHEVELLE]

Originally Posted by deuce_roadster

Any chance this engine got overheated and affected all the rings in a bad way?

Engine block and heads were baked, steamed, and run through a cleaning machine to get all the scale out. No over heating since the rebuild. I have a cylinder leak down tool coming and will run the test and post the results.

[philipswanson]

So what's the latest on this interesting story?

[Millerblt]

I have been following this discussion and there have been a lot of great suggestions so I thought I would throw in my 2 cents worth. My 36 Cabriolet shows 60 PSI in 6 cylinders and 50 PSI in the other 2 cylinders, (needs a valve job) but it starts and runs nice on 6 volts. Others have suggested it so I will add my vote with ignition or fuel.

[L78CHEVELLE]

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Originally Posted by philipswanson

So what's the latest on this interesting story?

Got the leak tester and hooked it up to each cylinder at top dead center. I put 100 psi into each cylinder and got the following results:
#1 cylinder held 90 psi
#2 cylinder held 65 psi
#3 cylinder held 60 psi
#4 cylinder held 65 psi
#5 cylinder held 75 psi
#6 cylinder held 90 psi
#7 cylinder held 75 psi
#8 cylinder held 75 psi
Each cylinder tested lost the air pressure through the intake valve with air coming out of the block on the intake valve opening. My questions are: 1. Why would a new engine that was good for 2,000 miles develope an intake valve leak on 6 of 8 cylinders in such a short time? 2. Will new intake valves from a different manufacturer correct this issue? 3. Since cylinder 1 and 6 are the simplest to find top dead center on and both of them have acceptable readings have I missed TDC on the other cylinders? I did do a compression test with the engine turning over with the starter on some cylinders with the same readings as the leak down test on the chosen cylinders. Any thoughts or comments? I think I have found the problem, but again WHY??

[paul2748]

Do you have adjustable lifters?

[L78CHEVELLE]

Originally Posted by paul2748

Do you have adjustable lifters?

Yes, the engine does have adjustable lifters.

[Tinker]

Looks like they didn't all change this time at the same level.



I'd lap the valves before just replacing them. That would take some time.

Check you lashings on each cylinder tdc again maybe.


Could be rings too I guess... Best of Luck!





.

[cas3]

glad you got some data to study. 1st, i am not a motor wizard, but lucky for you we have some here at the barn. next, i am confused, you say "air out the block whe intake valve is opened" well, intake air should come out the carburater, not the block. how, and why would you open the valve? the point is to see if its leaking, then record the data and move on to the next one. you have the intake manifold off, so its not going to be so easy and obvious to hear air out of the block as it would be with just the breather pipe, but air out of that area is ring leakage. if we have it narrowed down to burnt valves, only two possibility's come to mind, you set the lash with the cam not in the correct location, or your adjustable lifters moved. at any rate, to proceed on you cant just drop new valves in and have it rite. first of course, pull the old ones out and try to see if it burned the seat or the valve, or both. then, you will need to set up the new valves in the car, if you choose. to do it rite you will need a valve machine to atleast check the new valves, and a seat cutter to do the seats in the car. it can be done, its messy and the utmost effort to clean your mess up is essential. well, thats my backyard opinion, lets see what real motor guys say....best wishes

[Tinker]

Had a burnt valve on my 36coupe. Looked like this... Still had 30psi on that cylinder.






Replaced it with a used/pre-run nos assemble from someone here for 7$. Lapped it and installed. 90psi. Been driving it for yrs now. The 36 is not equipped with a "barn burner" engine, mind you.



These were original valves, Hard to believe your valves are burnt in 2000 miles. But just a reference on what a burnt valve looks like. Intake valve, most likely due to running lean for a very long time.

[Tinker]

You are knee deep in now. But sometimes using a vacuum gauge on the intake can help to understand internal issues quite well before teardown.


Interested in the results.

[Russ/40]

As I said before, the symptoms scream burnt valves. Its time to pull the motor. It all needs to be inspected to see what needs to go and what you can keep. In jeopardy I would say: Valves, seats, lifters, cam, and rings. Be prepared for the worst and maybe you'll be lucky. Don't try to do it in the car, that's crazy. I wish you were closer as I'd love to help. Send me your valves and I'll check them and resurface them for you gratis. PM me. Good Luck,

[L78CHEVELLE]

Originally Posted by cas3

glad you got some data to study. 1st, i am not a motor wizard, but lucky for you we have some here at the barn. next, i am confused, you say "air out the block whe intake valve is opened" well, intake air should come out the carburater, not the block. how, and why would you open the valve? the point is to see if its leaking, then record the data and move on to the next one. you have the intake manifold off, so its not going to be so easy and obvious to hear air out of the block as it would be with just the breather pipe, but air out of that area is ring leakage. if we have it narrowed down to burnt valves, only two possibility's come to mind, you set the lash with the cam not in the correct location, or your adjustable lifters moved. at any rate, to proceed on you cant just drop new valves in and have it rite. first of course, pull the old ones out and try to see if it burned the seat or the valve, or both. then, you will need to set up the new valves in the car, if you choose. to do it rite you will need a valve machine to atleast check the new valves, and a seat cutter to do the seats in the car. it can be done, its messy and the utmost effort to clean your mess up is essential. well, thats my backyard opinion, lets see what real motor guys say....best wishes

As I stated earlier the intake is off the engine. The exhaust and intake valves on each individual cylinder are closed when I put the 100 psi of air pressure into each one of them for testing. When I put the air pressure into the cylinders the air escapes out of the intake opening in the block on every cylinder tested. I would have thought the hot exhaust valve would have been the problem, but the intake valves are the problem?? Does not seem like the intake valve would be damaged and the exhaust not damaged on a new rebuilt engine. Next step is for me to pull the heads and look at the valves. Maybe the valves are sticking on the intake side. Every piece in this valve train was new when rebuilt.

[Russ/40]

I suggest you remove the 2000 miles since build from the equation. Its coloring your perspective of what can be happening. A lot of bad things can happen in far less than 2000 miles.

I have to compliment you on your stick to it ness. Getting the heads off is a major step to resolving your problem. Your going to beat this. You really don't want to do any valve seat work in the car. I would make an exception if the condition suggests lapping only. Wet lapping controlls the mess well. My valve reconditioning offer stands if your inclined. I'd like to help, no cost offer.

[tubman]

Take Russ at his word about the valves. He did the same for me and they turned out great.

Thanks again, Russ!

[rotorwrench]

A leak down test is the best way to find out where the compression is going. Carboned up valve seats can leak, stuck valves, and gooped up compression rings can all cause leakage. MMO down the throat will loosen the sticky stuff up. Low time since overhaul engines shouldn't have a lot of ring wear yet unless it's been huffing dirty air or running too rich for too long.

[Tinker]

I think the op is well beyond a mmo lube now. I mentioned it 3 pages back, not sure if it was tried. My 38 truck rebuilt engine stuck real bad with new guides/valves after a yr. mmo cleared it up. Flatheads were designed with leaded gas in mind (upper cylinder lubrication).


Probably not the issue though. Motor would have bucked under load with sticky valves. Which would have been seen easily with a vacuum gauge too. Think the poor performance is due to compression loss. Hard to say....


.

[L78CHEVELLE]

Originally Posted by Russ/40

As I said before, the symptoms scream burnt valves. Its time to pull the motor. It all needs to be inspected to see what needs to go and what you can keep. In jeopardy I would say: Valves, seats, lifters, cam, and rings. Be prepared for the worst and maybe you'll be lucky. Don't try to do it in the car, that's crazy. I wish you were closer as I'd love to help. Send me your valves and I'll check them and resurface them for you gratis. PM me. Good Luck,

Russ, your offer to help has given me encouragement to continue even with my limited knowledge and resources. I will take the heads off next week after my legs and back recover from the work and testing I did last Friday. I will post what I find when I get the heads off.

[Russ/40]

Originally Posted by L78CHEVELLE

. I will post what I find when I get the heads off.

I bet your back hurts. It gets old real fast.

Another possibility occurred to me today. A few years back there were some bad valve guides on the market. They wore real fast. When your back stops killing you, try selecting an intake valve in the worst cylinder, completely seated ( some lash to know its fully seated) and grab the bottom of the valve stem and see if you can move it back and forth. A severley worn guide will prevent the valve from seating fully and compression will be lost.

Your going to get this figured out, and when you do we all will have learned a lot.

[philipswanson]

Your going to get this figured out, and when you do we all will have learned a lot. [/QUOTE]

I second that!

[L78CHEVELLE]

[QUOTE=L78CHEVELLE;1748383]Got the leak tester and hooked it up to each cylinder at top dead center. I put 100 psi into each cylinder and got the following results:
#1 cylinder held 90 psi
#2 cylinder held 65 psi
#3 cylinder held 60 psi
#4 cylinder held 65 psi
#5 cylinder held 75 psi
#6 cylinder held 90 psi
#7 cylinder held 75 psi
#8 cylinder held 75 psi
Each cylinder tested lost the air pressure through the intake valve with air coming out of the block in the intake valve opening.

Today I took both heads off the engine and took all the valves out of the block. Here is what I see: #2 cylinder intake valve guide was stuck in the block when I tried to take it out. Surface sealing of the #2 intake valve against the seat was not uniform around the intake valve rim. Same deal on cylinder 3, 4, 7, and 8. Intake valve guides were stuck in the block, and surface sealing of the intake valve against the seat was not uniform around the intake valve rim. The exhaust valve guides were not stuck and the exhaust valve rims look like they were making an acceptable seal with the exhaust valve seat. I am going to clean up the valve seats and go with new stainless steel valves, new one piece guides, and new Mercury heavy duty valve springs. Looks to me like all this trouble and time lost is nothing more than a bad valve job on a low mileage rebuilt engine with less than 2000 miles since the rebuild. Odd the intake valves are the problem to me, and the compression decreased so quickly and uniformly on 6 of the 8 cylinders. What do you think?

[Ross F-1]

Originally Posted by L78CHEVELLE

Today I took both heads off the engine and took all the valves out of the block. Here is what I see: #2 cylinder intake valve guide was stuck in the block when I tried to take it out. Surface sealing of the #2 intake valve against the seat was not uniform around the intake valve rim. Same deal on cylinder 3, 4, 7, and 8. Intake valve guides were stuck in the block, and surface sealing of the intake valve against the seat was not uniform around the intake valve rim. The exhaust valve guides were not stuck and the exhaust valve rims look like they were making an acceptable seal with the exhaust valve seat. I am going to clean up the valve seats and go with new stainless steel valves, new one piece guides, and new Mercury heavy duty valve springs. Looks to me like all this trouble and time lost is nothing more than a bad valve job on a low mileage rebuilt engine with less than 2000 miles since the rebuild. Odd the intake valves are the problem to me, and the compression decreased so quickly and uniformly on 6 of the 8 cylinders. What do you think?

I'd assume the stuck intake guides had seals on them, the exhausts did not? A pretty common situation.

It sounds like you're lucky 2 of the cylinders had compression, it does sound like a bad valve job.

[Russ/40]

Did you perform the test I suggested in my post #80?
What was the valve to guide fit like?

[L78CHEVELLE]

Originally Posted by Russ/40

Did you perform the test I suggested in my post #80?
What was the valve to guide fit like?

Russ, I did check the guide and valve on the worst cylinders and they show no play. All seem normal. Like you suggested I have gotten the 2000 mile rebuilt engine thinking out of my mind and am treating this as a valve job. I will be using a stone on the valve seats to clean them up and installing all new valve train components except the lifters. I will post my results and findings for all that have an interest.

[L78CHEVELLE]

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Originally Posted by Ross F-1

I'd assume the stuck intake guides had seals on them, the exhausts did not? A pretty common situation.

It sounds like you're lucky 2 of the cylinders had compression, it does sound like a bad valve job.

The intake and exhaust valve guides both had rubber seals on them. No exhaust valve guides were stuck in the engine.

[cas3]

when you get your new valves, just for confirmation, drop the new valve in, and check with the blue stuff to see where your contact area's are, and maybe get away with just lapping since its pretty new. long chance, but the reason i say this is you mention using a stone to do seats. in the car, a much cleaner method would be the new way seat cutters. easier mess to clean up, no stone grit flying around in your new motor. best wishes

[L78CHEVELLE]

Originally Posted by cas3

when you get your new valves, just for confirmation, drop the new valve in, and check with the blue stuff to see where your contact area's are, and maybe get away with just lapping since its pretty new. long chance, but the reason i say this is you mention using a stone to do seats. in the car, a much cleaner method would be the new way seat cutters. easier mess to clean up, no stone grit flying around in your new motor. best wishes

Good advise about grit in the new motor. I have been thinking about this valve job that has gone bad in a short time. I have watched several videos on You Tube, and have seen machine shops doing valve jobs with the stones that do flathead engines on a regular bases. The machine shops say they can not do a routine valve job on the flathead block in their machine, because the block will not fit into the machine. Maybe the machine shop that did my engine did not have anything to do the valve seats with, and that has resulted in this problem. I have noticed the good flathead Ford valve tools are very expensive. If a machine shop had to buy them to work on an engine design they do not get often they may have tried some other method. Who knows for sure. I am going to do this repair the best I can and praise the Lord and full steam ahead.

[Russ/40]

You will prevail. The machine shop that claims the work cant be done because it doesn't fit their machine is not a flathead mechanic and should not be doing the work. A "pilot" that centers the surfacing stone or cutter runs off the upper valve bowl and the lower tappet bore to assure concentricity. That is what went wrong in the first place. Did the prior valve job use split guides? If so, mixed up halves would add to the lack of a properly aligned valve job. How do you plan to proceed if you don't mind my asking? PM me if I can be of assistance.

IMPORTANT check the old valves. Are any bent slightly? Any signs of the valves hitting the heads? There has to be a sign somewhere of why this gradually occured.

[Tinker]

Call your shop and ask. Valve seats are multi angled. If you have these questions about the valves from the rebuild, I'd also question the bore too. But don't over think it. Call the re builder.

[L78CHEVELLE]

Just for an update to all that have an interest. I have purchased a Black and Decker valve seat grinder to clean up the valve seats. The stone I need to do the job is the 1 5/8, which came with my unit, but has a chip on the bottom of it. Also, the set did not have the flathead Ford valve guide adaptor so I had to find one of those. I am looking to buy a new 1 5/8 stone soon and start the process of cleaning up the valve seats. I will post new information when I have it.

[cas3]

thanks for keeping us up to date. i could have loaned out the pilot, but you got one. in your case, since it was done so recent, it may not need real grinding. first thing i would do is paint the seat with a magic marker or blue, and turn the stone by hand, and see what the heck is going on. do the same with a new valve and some compound. keep in touch!

[Russ/40]

Ideally you should use 3 stones, 30*, 45* and 60*. This enables you to position the final seat in the correct place, as well as give you control over the width of the seat surface. Google 3 angle valve job.

Curious, did you ever check all the valves for straightness, and potential head contact?

Happy to hear your on your way to getting it fixed. Let us know how it goes.

[L78CHEVELLE]

Another up date if you are interested. Hooked up the valve seat grinder today with the 1 5/8 45 degree stone. The valve seats on this engine are not smooth at all with gapes all around the seats. Did the seats on pistons one and two. After grinding the valve seats I could see a big improvement in the surface of the valve seats. I lapped the new valves on pistons one and two. Valves show a very good contact patch and seal all around. Appears to me the shop that did the engine did not have the Flat Head Ford adapter to grind the valve seats properly. Just a guess on my part. Bottom end of the engine looks very good along with the very clean water ports. Will do some more work and post the results for all that have an interest. I have ordered another tool that will attach to a drill and lap the valves much better than the hand twisting I have done in the past. Be about 10 days to get the new tool. Thanks for your interest, support, and encouragement. The situation now seems to be on the up swing.

[Mart]

That sounds like good news.

The shop that did the "work" should be ashamed of themselves.

To be honest if the seats have been ground it should only take the slightest amount of lapping. It should be easily achievable by hand. Why not try the ones you have done?

Mart.

[L78CHEVELLE]

For those interested here is the latest with this project. Today I did the stone work on all the valve seats. The valve seats that had 60 to 65 compression needed about 7 seconds of grinding to clean them up and remove the dye. The two cylinders that had 90 compression only needed about 3 seconds of stone grinding. This engine should show a big improvement in performance now. Will do the lapping of the seats and valves when the new tool arrives. Will post new findings when they happen.

[cas3]

seven seconds is a lot. be careful, or you will end up with the seat very low on the deck. check often, i like magic marker pens

[cas3]

i gotta add some more or i will lose sleep on this one! normally, you have a spring on your pilot, and you only briefly touch down on the seat, and the spring pushes the stone off. briefly, as in, the stone cuts quick. if you are grinding for seven seconds, you cut the hole bigger, and put the seat out to the edge of the valve. and, if really grinding for 7 seconds, its darn near time to true the stone again. and theres that much more stone grit to clean up. if your motor builder guy really had the seats that far off, well maybe your new pilot is trying to make a whole new center. with the 3 different stones it can be done, but you end up lower, and lower in the deck. you want the actual seat contact about a 1/16th in from the outer edge of the valve when done, and the valve slightly proud of the deck. i hope i am telling you things you already know, best wishes

[flatheadmurre]

If the seat is off center is one thing...but if the guy doing it with a cutter got so much shatter it´s not consistant is another thing.
I see a lot of seats coming it done with a not so sharp cutter that seal poorely...
Stones makes a beautiful job...that we use 3-angle cutters and seat and guide machines is just to cut down the time used...not that it makes a much better job...

[L78CHEVELLE]

Originally Posted by cas3

i gotta add some more or i will lose sleep on this one! normally, you have a spring on your pilot, and you only briefly touch down on the seat, and the spring pushes the stone off. briefly, as in, the stone cuts quick. if you are grinding for seven seconds, you cut the hole bigger, and put the seat out to the edge of the valve. and, if really grinding for 7 seconds, its darn near time to true the stone again. and theres that much more stone grit to clean up. if your motor builder guy really had the seats that far off, well maybe your new pilot is trying to make a whole new center. with the 3 different stones it can be done, but you end up lower, and lower in the deck. you want the actual seat contact about a 1/16th in from the outer edge of the valve when done, and the valve slightly proud of the deck. i hope i am telling you things you already know, best wishes

Lot of good advise here. The 7 seconds of grinding is not all at one time. I did about 2 seconds and checked it. Still had dark spots of die. Did the grind again for about 2 seconds and still dark spots. Ended up with about total of 7 seconds on three of the seats. What else can you do if the seat does not clear up and the dye disappears? I saw no alternative but to grind the dye away. Will lap the valves and see what I have. Had an engine that would not run before with the valve seats the way they were. Hoping for the best and trying to make a better situation out of a bad situation.

[flatheadmurre]

Was the dye all on one side or did you have low spots around the seat ?
If they used the guide with a 11/32 pilot and it wobbles around you don´t get a consistent cut...you have the cutter/stone shatter around badly.

[L78CHEVELLE]

For all that are interested here is where my situation is. When I started this I thought 3 days and it will be done. It has taken 3 months to get where I am now. To make a long story short I had a friend come by on Memorial Day that has flathead engine experience. The valve base in the engine measures 1.5 inches. We measured the valve seat in the block and found it also to be 1.5 inches. We took a 30 degree stone and ground all the seats to narrow them down to 1.4 inches. Lapped the new stainless steel valves and the lap line was about 1/16 inch wide in the middle of all the valves base. Put the engine back together and did an air pressure leak down test. Compression was 60 to 80 lbs. on the cylinders. Put a 6 volt battery in the car and did a compression test with the starter. Same readings of 60 to 80 lbs. on each cylinder. Really discouraged at this point. Prayed about it and decided we had nothing to lose by putting in a 12 volt battery and doing a compression check off the starter. Turned the engine over with the 12 volt battery and we got 120 lbs. of compression on each cylinder. Now what? Why is this happening? Went and talked to an older worker at a local machine shop. Told him the measurements on the valve seats, told him what the valves looked like after lapping, the compression readings for all the ways we checked the compression. He told us he had been in this same situation before and could not explain it. He told us if everything looks good put it together and drive it. So, we put it together not knowing anything else to improve the situation. Got the engine together and hit the starter with the 6 volt battery. Engine started up and sound very good. Ran it until it got up to normal temperature and shut the engine off. Hit the starter again and the engine started instantly. Car has more power than it did, starts better than it did, and runs cooler than it did. I have been driving it as the weather permits with improving performance from the engine each time I drive it. Cannot explain the difference in the compression checks mentioned, but it is greatly improved over what I had when I started. Starts, runs, and drives with ease. I am going to drive it for a few more weeks before I even think of doing another compression check. What do you think about all this?

[cas3]

well by golly that is good news. odd that readings between 6 and 12 volts should change, more cranking rpm "should" have nothing to do with it. you spin the motor over 3 times when checking your compression gauge? at any rate, happy motoring, and i would do a couple quick oil changes to be sure of getting the valve grinding crud out. best wishes, skip

[JSeery]

All's well that ends well!

[tubman]

When you took the 6 volt compression check, did you block the throttle open and let it cycle through at least 4 compression cycles on each cylinder?

[ford38v8]

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Maybe I missed it, but I didn't see anywhere that you did the compression checks with a warm engine. Perhaps all the checks were with a cold engine except for the final check while warm? I'm thinking warm vs cold would give very different readings.

[L78CHEVELLE]

Originally Posted by tubman

When you took the 6 volt compression check, did you block the throttle open and let it cycle through at least 4 compression cycles on each cylinder?

Intake was completely off the engine, so intake area was open.

[L78CHEVELLE]

Originally Posted by ford38v8

Maybe I missed it, but I didn't see anywhere that you did the compression checks with a warm engine. Perhaps all the checks were with a cold engine except for the final check while warm? I'm thinking warm vs cold would give very different readings.

All compression checks I did were cold engine. Great deal of work to put all the engine back together to do a warm engine check not knowing if the problem was corrected.

[19Fordy]

L78: Love your tenacity. Glad you didn't give up. Keep driving and keep us informed.

[tubman]

120 lbs compression with a cold engine before the rings are seated? Even on 12 volts, I don't think you have anything to worry about.

[cadillac512]

First, well done. You now have a proper valve job. As for the compression discrepancy, a slow cranking engine gives more time during the test for the air in the cyl to leak past the ring end gaps and the relatively dry cylinder walls you may have had at the time of the tests. My tired '41 flathead checked at 70# with a 6V battery and now checks at 105# on 12V. My guess is you're going to be just fine now that the compression isn't being pushed past the poorly sealing intake valves and into the manifold. That situation makes for a very poor running engine. Well Done!


Terry