camshaft (Long)
 

I have never had an A engine totally apart. My question is - can a model A "jump" timing if the camshaft thrust plunger is not doing it's job because of a weak spring or some other reason? Reason I ask is because after complete trouble shooting the timing and entire ignition system the engine runs fine at idle and a little above. However when the advance lever is pulled down the engine will "bog" down and eventually quit. The distributor plate lever is touching both sides of the housing at full advance and full retard. Note, again, that this is happening with the advance lever being pulled down from full retard. I did pull the distributor shaft housing and shaft gear and could see no problems. The steering box is 7 tooth so no adjustment is available there but the dist. plate arm adjustment is okay as stated above. Timed with NewRex tool and once again the entire ignition system was trouble "shooted" and no problems noted. The carb was taken apart and rebuilt 2 times so carb. problems should not exist as the condition is all related to the spark advance - so I think. I have no way to know if it is going more retarded or advanced when it bogs down. I know how to determine with a timing light but I don't believe they even existed in the model A days and this problem should be fixable without one. The problem started with an erratic miss which could not be pin pointed to any one cylinder and occasional back fire when rapidly letting up on the gas pedal at higher RPM's when it was running. So I fixed it till it's really broke. O, yes the point gap is .017 and rotor to housing contacts all the same @ .025.

John

John

Re: camshaft (Long)
 

Point gap may be too close for stock. I run mine at .020. Service Bulletins from April 1930 say .018-.022. I dunno about any other system.

Re: camshaft (Long)
 

Is this a continuation of the previous, 'fixed till broke' thread ?

Re: camshaft (Long)
 

I have tried everything from .017 to .020

John

Re: camshaft (Long)
 

Yep. John

Re: camshaft (Long)
 

It is unlikely that the timing gear has jumped a tooth or two. But there is an easy way to check without taking the engine apart. First a little theory. The piston is at top dead center (TDC) for two times during the 4 stroke cycle. The first time the fuel is igniting and pushing down on the piston to start the power stroke. The second time the cylinder is switching from the exhaust stroke to the intake stroke. At that TDC both valves are slightly open.

The timing detent in the timing gear on the camshaft is used to locate TCD for the power stroke for the #1 cylinder. At the same time the #4 piston is at TCD switching from the exhaust stroke to the intake stroke.

Take all the plugs out. Leave the ignition and fuel off. Rotate the engine until the timing pin drops into the detent in the camshaft timing gear. Use a bore scope or other tool to check that the #1 piston is at TDC. The timing can be off a few degrees and the piston will still look like it is at TDC. Now check the valves on the #4 cylinder. The both should be just slightly open. If the cam timing is off, one valve will be closed and the other will be open about 1/4 inch.

The timing gears are helical cut, not straight cut, so I guess it is possible for the timing to change if the cam shaft is moving forward. If the cam plunger and spring are completely missing then I guess the timing could change to the point where the engine performance would be compromised.

Re: camshaft (Long)
 

If the engine bogs down when you pull down on the timing lever then either the timing is way too advanced or there is a fault with the distributor. I know you said that you have checked the ignition system, but it is still ignition related, so something is still wrong. Pulling down on the timing lever will advance the timing.

Check to see if the top plate in the distributor is not loose so that when you move it the point gap is changed. Also check that the wire that leads to the plate underneath does not have a bare spot that is rubbing against something.

The timing method on a Model A is pretty fool proof. Assuming the cam is timed correctly, the points should just be opening when the timing lever is full up and the timing pin is in the detent. If not then it is not timed correctly.

Lots of people use a timing light and degree wheel on a Model A to check the timing. The mechanics are the same as a modern engine. You can buy the parts from the vendors. Instructions come with the parts.

Re: camshaft (Long)
 

Did all that. I'm talking about the gear on the shaft that goes from the oil pump to the distributor. The shafts are all slip tight at the unions. I realize that top dead center observation in the spark plug hole could have a few degrees of crankshaft rotation but that should be a non-issue. I don't mean to be a smart a** on any replay - some may take it that way, I just need help.

Thanks, John

Re: camshaft (Long)
 

Got all this checked and even replaced the distributor with one out of my
speedster that ran great on the road 10 mins. before the swap and all the problems are the same. I know I am missing something somewhere but two other A people have looked over my shoulder, we are all stumped. BTW, I replaced the cam gear a couple years ago because the old one had a lot of slack between the phenolic center and the ring gear. I did check the points opening with a trouble light.

Thanks, John

Re: camshaft (Long)
 

Well, John, It sounds like you have done everything I can think of and done it correctly. I am stumped too. I will have to think about it.

If the engine is getting the right fuel/air mixture, the compression is good, and the spark is at the right time and a hot spark, the engine should run well. Have you tried a different coil and high tension wire? A marginal spark will not jump the gap at the plug under compression. It will look good at atmospheric pressure but not under compression.

Re: camshaft (Long)
 

I did try a different coil and wire. I only checked the compression the old time way with my thumb in the spark plug hole. As I said every thing I changed I took off my good running speedster. As an aside I have had the engine running smooth on one cylinder taking one plug wire off at a time, I didn't think a 4 cylinder engine would do that but when tuned properly it will. I fool with hit & miss engines and some will run good by pulling the flywheel through with my thumb and fore finger, I doubt more than 3 or 4 to 1 compression ratio - if that much. I also run 2 hit & miss 8 cycle engines - figure that one out. I am really stumped.

Thanks, John

Re: camshaft (Long)
 

Can you borrow a compression gauge and get some accurate numbers? You may want to use a vacuum gauge too. See the thread about the vacuum gauge.

Re: camshaft (Long)
 

I will do that, will take a couple days due to other commitments and will need help with the results as related to this problem.

Thanks, John

Re: camshaft (Long)
 

Let's return to the OP's original question: "My question is - can a model A "jump" timing if the camshaft thrust plunger is not doing it's job because of a weak spring or some other reason?"

The answer is Hell, yes! The spring may be weak or simply broken. I chased this all over the ignition, timing, compression, and fuel delivery universe before discovering a broken camshaft thrust plunger spring. I kept checking and adjusting every parameter of normal running, the engine would start and run correctly until I braked, made a sharp turn, shifted gears or scratched my arse, then it all fell apart, with backfiring, loss of power, etc.

Pull that front timing cover and tell us what you found.

Re: camshaft (Long)
 

But are you running stock?

Re: camshaft (Long)
 

When I read "jump timing", I thought you meant can the gears change due to the cam gear moving forward and out of mesh with the crank gear. The answer to that is no, but the spark timing will change due to the camshaft moving forward and rearward some if the spring is broken.

Re: camshaft (Long)
 

Yes, John

Re: camshaft (Long)
 

Thanks Tom, on the way to the shop to put things together so I keep from tripping over parts (in the AM). Then unto the timing cover, any thing else to check with the cover off for good measures?

John

Re: camshaft (Long)
 

ursus was on the spot with several symptoms, so timing cover next - nice to have Tom's advice to go along. I may have been demoted to Newbie. What size is that slippery little roll pin that was a booger to get out with the engine in the car and is it hardware store quality?

Thanks, John

Re: camshaft (Long)
 

Mouse nests clogging the exhaust? Or a backfire dislodging baffling in the muffler? That can mess up how an engine will run. I know that doesn't jibe with all the symptoms but if all else fails.....

Re: camshaft (Long)
 

Don't think so but wish it was as that would sure to be easier to check than the timing cover plunger spring,

Thanks, John

Re: camshaft (Long)
 

Check the timing cover isn't a B. It's more advanced.
http://www.fordgarage.com/pages/timingcovers.htm

Re: camshaft (Long)
 

[QUOTE=updraught;2050786]Check the timing cover isn't a B. It's more advanced.

It is not a "B" Thanks, John

Re: camshaft (Long)
 

These things can be fitted under the valve cover. No manual advance needed then.
http://www.fordgarage.com/pages/nurexadvance.htm

Re: camshaft (Long)
 

I would like to find the problem with the original set up. I did run a Mallory with a centrifical advance for a while but got tired of fooling with the springs to get what I felt was a decent curve.

Thanks, John

Re: camshaft (Long)
 

I'm not saying to fit one, but if a previous owner has fitted one it may not be obvious.

Re: camshaft (Long)
 

Have you checked for a vacuum leak?

Re: camshaft (Long)
 

I can't think of any roll pin. Where is it located?

The only pins I can think of is the two dowel pins for the cam gear.

Re: camshaft (Long)
 

I was wondering the same.

Re: camshaft (Long)
 

check valves condition,compression and leakdown,tappet clearance,stop throwing parts at it.

Re: camshaft (Long)
 

Post 28 & 29. Check Bratton's oil pump distributor drive gear sleeve. Mine would not come out with out removing that top shaft about 1" or so long.

Thanks, John

Re: camshaft (Long)
 

Go through the entire thread starting with the first one and tell me what was wrong with my trouble shooting and where I was throwing parts at it. Valves have less than 500 miles since installation by a reputable shop, it has no tappets and the valve stems were ground for proper clearance. I still say it is an ignition problem and compression and leak down should be non-issues. I may be wrong but I am going for the walking cam shaft theory because of a possible broken or weak plunger spring as others have suggested. No way to trouble shoot that without pulling the front cover that I know of. If you know of a way let me know as I have just jacked the car and do not relish going the rest of the way. Changing parts was a double check. I did find a distributor bad that a friend loaned me that he had timed and under his back seat for emergency road repair. He is glad we found it now rather than when or if needed. There was another thread on this titled "Fixed till broke"

John

Re: camshaft (Long)
 

I'm not sure of you look in the side cover [ light and maybe a mirror ] to see the plunger.

Re: camshaft (Long)
 

I guess that is possible, I will check but even if it is not broke I would have no way of checking the strength.

Thanks, John

Re: camshaft (Long)
 

john did not mean to upset you you changed the dist> and coil to no avail,yes it has tappets we call them lifters today.i would want to know the compression and if the cylinders will hold in a leak down test,nothing to take apart and all to gain.i think you said problem gradually worse not all of a sudden,possibly rebuilder left out the plunger spring? Best of luck hang in there you will find the problem.

Re: camshaft (Long)
 

Not upset at all, My understanding is that the engine does have tappets but they are not adjustable and the valve clearance is obtained by grinding the valve stems - 500 miles ago so the clearance should not have changed since that time. This is not a rebuilt engine, it was out to change the clutch and the valves were done than, I figured what the heck do the valves the machine shop was almost next door. It was more like a skip than miss. I did pull all the plugs, cleaned, replaced and ran the engine for about a minute. The skip was still there and all the plugs had about the same amount of soot. The engine ran fine at idle and slightly above but would "choke " down when the advance lever was brought down a little bit, moving it further down it would quit. I will do a compression test better than thumb over the spark plug hole method. Once again sorry if my response to your post sounded that I was upset with what you said.

John

Re: camshaft (Long)
 

This all is giving me a head ache so I want return that. Ponder how my 8 cycle hit and miss engines work. Maybe start an O.T. thread with your chosen name.

Thanks, John

Re: camshaft (Long)
 

You have an Aermotor water pump !? Thats a rare monster. There is one in this area. Never have been able spend enough time to figure out how the thing works.

Re: camshaft (Long)
 

John,

You have stated several times that you think this is an ignition issue. The only thing that I can think of that would give you the response with your advance lever is that the engine is too advanced or becomes too advanced. Check the plunger in the front. It is not too hard to do. But before that try a timing light. You can just put a mark with a bit of paint on the front pulley at 12:00 at TDC. You don't even need a pointer or you can just jury rig something up. Nothing like data to help understand what is wrong. It will be easy to see if the timing is 25 degrees advanced or 50 degrees. You don't need exact numbers for this first test. Or if you want to be more exact, put another mark 25 degrees advanced of the 12:00 position (12:50). With a 25 degree advance (close to ideal) the mark for TDC at 12:00 will be at 11:10. To be on the safe side you can take the fan belt off for the test.

Re: camshaft (Long)
 

Regarding a hit and miss engine. The intake valve is opened by the suction in the cylinder against a weak spring. When the flyball governor senses that the engine is running too fast, it will open the exhaust valve and turn off the magneto. The engine coasts with air being sucked in and pushed out with the open exhaust valve. The intake valve will not open because there is not enough suction. When the flyball governor senses that the engine has slowed down it will allow the exhaust valve to close and a fuel/air charge will be sucked into the engine and ignited by the now working magneto. The magneto is not like a modern one but operates by moving a magnet in a linear motion.

Fascinating engines. It seems like they run forever.