I think my exhaust valves are burnt

[bdtutton]

Hello,
When I purchased my 30 Tudor it ran pretty good. It did have a little bit of a stumble during idle, but overall it ran well. I have put about 10,000 miles on it since then and it still runs well going down the road, but stumbles more than before during idle and you can hear it in the exhaust.

As far as I know the engine is completely stock, does not burn any oil and when i change the oil it still looks clean....I pulled the spark plugs and did a quick compression check about an hour after a long drive...so the engine was warm, but not hot. cyl #1-55psi cyl #2-63psi cyl #3-35psi cyl #4-65psi.

My gut feeling is a burnt exhaust valve on the #3 cylinder and the #1 cylinder may be suffering too. I see things on forums about marvel mystery oil working wonders, but I think that is on cars that have been sitting, this is a daily driver. I think it may be time to pull the head and inspect the valves, but I wanted to ask some expert opinions before just tearing into the engine.

What do you think?

[RandyinUtah]

Pull the head and the side valve chamber plate and take a look. Not that hard of a job and then your going to know for sure.

[mike657894]

throw a little of the old red down it and see if it straightens out. then I would pull the side cover and roll it over and look to see if cyl 3 valves are coming down then take off the head and valve job/replacement. i gave my engine a new set of valves. set at .015 gap.

[TerryH]

Many Model A’ers regularly use MMO.....4oz per 10 gallons of gas.....

[bdtutton]

I guess I will order some gaskets and prepare to pull the engine apart....but I do have a follow up question. I live in Southwest Michigan and I was wondering if there is anyplace that I could just take the car and have the service done...like I would in a modern car.
I know that when you own a model A you have to plan on fixing your own car, but I work full time and have a family so my free time is limited. I am not in a club so my only contact with other model A owners is through this forum.

[Dick Steinkamp]

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You could perform an abbreviated version of a leak down test.

Get #3 to TDC on the compression stroke, then with your air compressor and the proper fitting, charge that cylinder with compressed air...maybe 30-40 PSI.

Listen for where the air is leaking out (exhaust pipe, carb, oil filler tube) and look for bubbles in radiator. That should tell you what needs repair (exhaust valve, intake valve, rings, or head gasket).

Even if you are not in a club, you can contact one and there are probably folks there that would help.

[Keith True]

Before you get too carried away and start pulling the engine apart I think you should first pull the valve cover.Check the valve lash,if it has original lifters then you will have to pull the head to adjust the.If it has adjustables you can set without pulling the head and buying an expensive head gasket.Is there something going on that points you to,burnt,instead of,tight valve? I won't say burnt valves are a thing of the past,but they are a lot more rare than they used to be.In the 70's I used to see a lot of farm tractors burn the valves.Now I see the same tractors with loose and rattling valves,but not burnt.

[Purdy Swoft]

More gap or lash on the valves gives more time for the valves to remain on the seat . More time on the seat better cools the valves and reduces the risk of burnt valves .

[Purdy Swoft]

I read that Henry said with a little noise the engine will keep its poise .

[Purdy Swoft]

I would always suggest that pulling the head should be a last resort . The chance of wringing off a head stud in the block can be a big risk either when removing or replacing the head .

[CWPASADENA]

[QUOTE= I won't say burnt valves are a thing of the past,but they are a lot more rare than they used to be.In the 70's I used to see a lot of farm tractors burn the valves.Now I see the same tractors with loose and rattling valves,but not burnt.[/QUOTE]


I agree that burnt valves are not very common today. I have a 31 Vickey that I bought several years ago. The engine in it had major work done on it back in the early 80's. All the exhaust valves are marginal and are not sealing at all well at all. The compression is down a bit and I can tell it is down on power but it still idles OK and runs good enough for around the town driving until I can find time to get all involved with rebuilding the engine and transmission.


I think running the valves extra loose will have little to no effect on the exhaust valves especially if they are already starting to burn. Once the exhaust valves start to deteriorate and do not contact the seat well, you have lost a most of the heat transfer from the valve to the seat.


Hard seats and better material in the valves will do wonders to longer exhaust valve life.


My opinion,


Chris W.

[BN]

I agree with Dick S. Do a diagnosis first. Obtain (or make from an old spark plug) an air fitting that will screw into the spark plug hole on #3 and hook up a compressor hose to it. Do the abbreviated leak down test. You will need a compressor, but a small one will work fine. Where you hear air escaping will tell you what's wrong. Carburetor = intake valve, exhaust pipe = exhaust valve, oil filler tube = rings or hole in piston, bubbles in radiator= head gasket. I would set the parking brake and chock a wheel in case the piston is not exactly at TDC.

[BN]

You should probably do a leak down test on another cylinder to compare air leak noises.

[Railcarmover]

squirt oil in #3 and repeat the compression test,if it comes up its rings,if it stays the same its valve. I you find an outside shop that will do the repair,look for two things..experience doing model a's and being capable of doing a correct diagnosis, start any repair with a shop with a 'diagnose and advise'..it helps avoid sticker shock,that unsettling phone call that starts with 'we found' after you authorized repair.

[Purdy Swoft]

After the symptoms appear and the valves are burnt, its too late for adjustment to solve the problem . I set my valves , intake and exhaust at sixteen thousands . Snyder's recommended this setting several years ago and it has worked well for me . I use this setting with original cams and my Winfield 3/4 race regrinds .

[Railcarmover]

Retrofitting modern valves and seats cure the burned valve issue through advancement in metallurgy.I run a 'C' grind cam (high lift B) with a .015 clearance based on this. Ford recommended a .022 clearance originally,to help cure the burn issue.Seat duration,as stated before,cools valves..if you run original ford valves pay heed.

[Wick]

Are the plugs a consistent color? Is #3 very white or oily looking. A scope on a cell phone can give you a look at the valve head. Could just be a head gasket leak.

[bdtutton]

My spark plugs all look good and are a consistent color. I guess my next step is a leak down test. My gut feeling is a leaking exhaust valve.

[Patrick L.]

Originally Posted by bdtutton

My spark plugs all look good and are a consistent color. I guess my next step is a leak down test. My gut feeling is a leaking exhaust valve.

The leak test is the best and easiest way to find out. Generally a burnt valve will show a compression reading of zero. If it is a valve then it is just starting to burn. It may just be sticking or not have enough lash,etc. If it is getting burned though it'll need to come out and be fixed. Its worth the time to find where the problem is before tearing to much stuff apart.

[Gary WA]

MMO helps lube top end valve stems etc.ethonal gas very dry! U know that.!

[30 Closed Cab PU]

Would a worn distributor also cause this at idle? Timing not stable. Am asking , do not know.

[CWPASADENA]

Originally Posted by 30 Closed Cab PU

Would a worn distributor also cause this at idle? Timing not stable. Am asking , do not know.

Yes, worn distributor components can cause inconsistent idle.


Chris W.

[30 Closed Cab PU]

Originally Posted by CWPASADENA

Yes, worn distributor components can cause inconsistent idle.


Chris W.

Then perhaps swapping in a know good distributor is worth a try before pulling the head.


Also perhaps inspect the valves through the spark plug holes with a fibre optic camera.

[Dick Steinkamp]

Originally Posted by 30 Closed Cab PU

Then perhaps swapping in a know good distributor is worth a try before pulling the head.

He says this in his initial post...

cyl #1-55psi cyl #2-63psi cyl #3-35psi cyl #4-65psi.

I don't think a different distributor will fix the compression on #3

[bdtutton]

I did a leak down test last night. I put 35 psi into cylinder 3 and it produced a loud hissing sound out the tail pipe, so it confirms my suspicions about the exhaust valve. I ordered a full gasket set (Including head gasket) and plan to pull the valve cover off tonight to check the clearances and to find out if I have adjustable tappets.
I ordered the gasket set from Macs and I picked the one with the silicone head gasket instead of the copper. They said it can be put on without any gasket sealer. Anyone have any experience with this type of head gasket??

[30 Closed Cab PU]

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Have you pulled the side/valve chamber cover as suggested? You may just have a sticky valve or a bit of carbon under the valve. A lot less work than replacing a head gasket that may have been on for a long time - difficult to get off. Research or ask about ways to fix a sticky or carboned valve. Some add/spray Marvel Mystery oil in through the carb Intake, or add to the gas and drive for a while, for the sticky valve issue.

[30 Closed Cab PU]

Sorry - need to read previous posts better - but there are things in previous posts to try.

[Tom Wesenberg]

Cancel the gasket order and buy the copper head gasket, so you won't have to pull the head again to replace the bad silicone gasket.

[bdtutton]

I have been busy doing other stuff so this has been a slow project. I pulled the manifolds, distributer and the valve cover plate. I found the engine has modern style valves and all the clearances are between .010 -> .018 and the tappets are adjustable. I loosened all the head bolts and realized the head is stuck on tight so I am going to spray some penetrating oil around the studs and I have ordered a head puller that will be here in a couple of days. I will see what the valves look like as soon as I get the head off. I only expect to see one bad one because when I did a leak down test on the other cylinders the biggest problem I had was keeping the engine from spinning because the valves were pretty tight. I wonder what caused this problem.

[Wick]

Put the plugs back in and spin the starter over with the head nuts loose/off. Head should pop loose.
Or fill 1 cylinder with rope and turn it over by hand.
I'm guessing seeing you have modern valves,that the valve may be bent or the seat is bad.

[bdtutton]

I ordered a head puller from Snyder's and still could not move the head until I soaked all the studs with penetrating oil for a couple of days. I finally got it off and found a lot of carbon build up on various areas. Just wondering what the best way was to get all the carbon off and opinions on replacing all the studs. I think I can get the rust off them and the threads are still pretty good. I am worried about busting the studs off in the block if I try to replace them with new ones. Any opinions ?

[Wick]

Carburetor cleaner will soften up the carbon,then scrape it off. Look on YouTube.
Replace the studs and nuts and have the head checked for cracks and flatness.
Double nut the studs,they should come out.

[bdtutton]

I tried all kinds of options to clean the carbon and found that just soaking everything with good old WD40 and scraping a little got off the rust and most of the carbon. I sprayed the head with WD40 a couple of times and scrubbed it with one of those scotch pad kitchen scrubbing pads. I then took it out in the yard and sprayed the head with a hose to clean everything off and it looks almost brand new. New respect for WD40.
.
The head bolts actually look pretty good so I decided to spray them with WD40 and run a nut up and down the threads to make sure they are clean. I am planning to use brand new head nuts because they are cheap and the old ones have some rust on them.
.
I found the engine had been bored out to 3.975", but the bore is smooth and round and the engine was not burning a drop of oil so I am not going to touch it. If I ever have a problem I will just have it re-sleeved back to the original bore size.
.
The 2 valves I am having a problem with were not really burnt, they look more like they were just poorly lapped in when they were installed. (Yes, it has hardened seats.) I thought about just re-lapping the two valves, but they also wobble a little like the valve guides are worn, so I plan to replace them all and lap them in properly.
.
Will report progress....

[30 Closed Cab PU]

If the bolts are old, have not been replaced for a long, may want to replace them with grade 8 with new nuts. Since the head is off, now would be a good time.

[bdtutton]

I keep thinking about replacing the studs, but I fear breaking one or more off in the block if I try to replace them. I know it is the right thing to do, but I had a couple of bad experiences years ago and I guess I still have not gotten over that fear.