Snapping sound under load.

[AzRay]

OK - This one is driving me nuts. Once my 1929 A warms up and is put under a load like driving up a steep hill I hear a very loud sound like a 'spark snap' which seems in time with RPM. No loss of power. If I retard the spark almost to TDC the sound goes away. Under a light load if I move the spark advance from TDC to full advance the sound gets louder. Once at the top of a hill the first time I rev the engine I get the same snapping sound. The second time the sound is less. The third time nothing! So whatever the noise is it's effected by the timing. TDC no noise. Full advance loud noise. New plugs, new plug wires (conductors), new points and condenser, new distributor cap and rotor, new coil and secondary wire. Any help will be much appreciated.

Thanks
Ray

[Jacksonlll]

Could be an exhaust gasket break. Easy to fix if it is.

[29spcoupe]

Could be spark knock. If your spark is advanced too far the spark is occurring before it should, thus fighting the piston travel. See if you retard the spark a little if it goes away. If the pinging starts when you first advance the spark, then your timing is too far advanced.

[AzRay]

Originally Posted by Jacksonlll

Could be an exhaust gasket break. Easy to fix if it is.

It doesn't sound like an exhaust leak and I'm hard pressed to understand how at a constant throttle just moving the 'advance lever' from full retard to full advance would greatly increase the volume of an exhaust leak. Won't totally dismiss your idea and will check for a leak in the morning. Let you know if I find one.
Thanks

[AzRay]

Originally Posted by 29spcoupe

Could be spark knock. If your spark is advanced too far the spark is occurring before it should, thus fighting the piston travel. See if you retard the spark a little if it goes away. If the pinging starts when you first advance the spark, then your timing is too far advanced.

As I stated before if I retard the spark fully or near fully the snapping sound stops. With the advance lever set about 1/2 way and if I go very easy on the throttle, no noise. Add throttle and the snapping begins.
I set the points between 20 and 22. Checked the timing with an ohm meter. I think I'm quite close. Is it possible for an engine with 4 1/2 to 1 compression ratio to 'ping'?

[29spcoupe]

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If you are not hearing the 'ping' with the spark fully retarded and you hear it when advancing, then the noise is spark related. The ping is not happening because of the compression ratio. Spark knock in higher compression engines occurs because the low octane gas ignites faster under high compression and therefore the adding of higher octane. If your timing is quite close with an ohm meter, is it possible that your distributor cam has moved a little causing the points to open sooner? My feeling is that it is timing. I would check everything again. I would like to hear what others think.

[SeaSlugs]

Originally Posted by 29spcoupe

If you are not hearing the 'ping' with the spark fully retarded and you hear it when advancing, then the noise is spark related. The ping is not happening because of the compression ratio. Spark knock in higher compression engines occurs because the low octane gas ignites faster under high compression and therefore the adding of higher octane. If your timing is quite close with an ohm meter, is it possible that your distributor cam has moved a little causing the points to open sooner? My feeling is that it is timing. I would check everything again. I would like to hear what others think.

I really dont know but going to sit and watch this as it unfolds and a solution is found. In regards to the timing it takes all of a wrench to reverse the timing pin, hand crank, and your eyeballs to see where rotor is pointing when the pin drops in. Deffinately cant hurt anything to check and check the point gap.

[AzRay]

I'll recheck the timing and check the points setting. However, if it's slightly advanced due to distributor cam slit then manually retarding the spark two or three clicks should stop the noise. It doesn't. I have to raise the lever full up to stop the snapping. I keep saying "Snapping" since it sounds like a secondary spark. Like you pulled a plug wire off and let it snap 2 or so inches to the plug. I've never heard a ping inside an 80 year old engine so don't know what it would sounds like. I thought about a possible ping since the engine is running very rich at the moment and I thought maybe the progression of flame in the enriched mixture could cause pre-detonation, even in a low compression engine. I'm grasping at straws here. Help! :-)

[larrys40]

my bet is an exhaust leak. You may have a crack in the exhaust manifold or possibly a gasket/issue at the block surface. Inspect the manifold well, on top, underneath where it goes under to mount to the block. Feel for exhaust gas while running.. careful not to burn yourself. look for sooty witness mark.

Unless you have severe piston slap.... or possibly a cracked/broken piston my bet is it's an exhaust leak. You can carefully try to tighten up the manifold nuts a little but honestly it probably needs a new gasket. For what you have I would use the one piece steel clad style - no gland rings ( probably would never fit anyway except on a new manifold).

I surface the manifolds together (preferrable if you're able to get that done) before re-mounting. Be watchful of the clamp connection and the alignment of the pipe to manifold and the flange. it's also a source of leaks and noise.
Larry

[Tom Wesenberg]

My stock engine had ping with the slightest acceleration, even with the spark at half way down. Turned out the cooling chamber had a lot of rust buildup in the rear of the block, and this caused a hot spot, which resulted in ping. It also caused the rear pistons to run too hot and slightly collapse the skirts. I flushed out the block and cured the ping, but I still have some light piston slap.

[H. L. Chauvin]

Sounds like you have advanced timing which is harmful for Babbit bearings.

Every Fordbarn expert has his own method of timing; and, every one of these methods is 100% perfect for each 100% Model A expert.

However, from over 20 years of reading Model A messages, "many" read volumes of Model A books and messages, and just continue to have a problem with timing.

Just expect many different perfect Model A timing solutions to follow, but here is what is most important for proper timing of a new or totally worn out Model A with loose play at the rotor, distributor shaft, or whatever ....... and remember ....... worn out Model A's will run very well without spark knocks after providing "proper" timing.

1. First set you point gap first. You did this.
2. Retard your spark with spark lever all the way up and very carefully time your engine.
3. At this point, "after" carefully timing one's engine, remove all four plugs and connect grounded no. 1 plug to the distributor.
4. With ignition switch "ON", spark lever all the way up, rotate engine with hand crank until timing pin slips in.
5. When timing pin slips in, no. 1 plug should fire when points open.
6. It does not matter if your rotor has free play, if your distributor shaft wiggles back and forth ........ if no. 1 plug fired when timing pin slipped in, you are good to go.
7. Just please try this just "once" to see what happens & let us know .... and if you do respond .......... you may be one out of thousands that never cared to learn and beat their Babbitt bearings to where they were always removing connecting rod shims.

[eagle]

I haven't ever heard a ping that sounds like a spark snapping. Gotta be something else. Ping has a very distinct sound to my ear. Actually, its a bit of an onomatopoeia.

[Mike V. Florida]

When did this start, before or after the new parts?
Is your distributor and wire system stock?

Does the engine miss when it's doing this?

[H. L. Chauvin]

From Mr. Eagle's reply no. 12:

"I haven't ever heard a ping that sounds like a spark snapping. Gotta be something else. Ping has a very distinct sound to my ear. Actually, its a bit of an onomatopoeia."

By far the most intelligent, elegant, and sincere descriptive response ever posted on a Model A Forum.

Most sincere thanks.

[Chuck Sea/Tac]

Have you looked in the engine compartment with it running ,in the dark?

[Mike V. Florida]

Originally Posted by Chuck Sea/Tac

Have you looked in the engine compartment with it running ,in the dark?

I'm thinking "leakage" also. That's why I asked about the new parts and if it is a stock setup.

[Mitch//pa]

I've learned to sit back on these things, as i hate to jump to conclusions. Just about everytime I / WE never receive all the info needed to come up with a logical response other than an arm chair guess. Usually more info squeaks out as the threads progress. I / WE have learned on post #8 that the engine is quote running very rich. No matter what the end result is, or what the source of the snapping sound is the cause of this condition needs to be corrected.

[Jacksonlll]

I like the run in the dark suggestion. If it sounds like a high voltage snap, then maybe it is. See where the spark is in the dark.

[macdonge]

Ditto on the dark suggestion. Sounds like the coil wire to the distributor may be loose or arcing.

[AzRay]

I want to thank everyone for all the great suggestions. Believe me, I'll try them all over the next few days. Someone mentioned blocked water jacket and I think I can check that with the same point and shoot temp gage I'm using to check brake temperature to adjust them. As for watching the engine in the dark. I already thought of that. There's only one problem. This only happens under a load and by the time I stop, squeeze out of the roadster's front seat, (Now I know why they always jumped over the door in the movies) and can look at the engine the snapping is gone. I did suggest to a friend that he rides in the left spare tire fender well while I drove but he wasn't too cool on that idea. However I think I'll let him drive and I'll ride on the fender.

Thanks Again. And I'll keep all informed on how this works out.

Ray