Stovblt & Paul,

I had thought my post was complete until I read Stovblt's. He did a masterful job of commenting.

I thought about piston slap and wrist pin noise but didn't want to confuse readers. I am glad that Stovblt did as it may be what is actually happening.

I agree with you that Stovblt’s response makes this a great forum.

I thought about his comments and think my problem is not being familiar with the sound of the engine.

I took the car for a drive and thought about both your comments.  I feel that I am not familiar with the sound of the engine. I think that I have been retarding the spark too much while climbing a hill or on acceleration. This is why I questioned the distance that the spark button traveled back to retard the engine. I need to feel that button does not need to be completely pulled back.

The car was quiet while idling and no knocking sounds, so I do not think it is a bearing. I will say that changing the spark plugs to .040 did make a difference in the performance of the car.  

My plan is to drive the car and get more familiar with it and then change the timing to 18 degrees BTDC. I will talk to a local mechanic about using a borescope next week.  

This is the first early 6-cylinder engine I have worked on as my experience has been with the early Chevy 4-cylinder engine. I own a 1926 touring and a one-ton truck.

Thank you for all of your help.

Paul

I wanted to update you on my 29 Chevy and thank you for all of your help. I set the spark plugs to .040 and it improved the performance. I rebuild the carburetor as well. What does increasing the spark gap accomplish? The car sounds and runs much better.

@paul-baresel increasing the gap size increases the spark area exposed to the air-fuel mixture, which maximizes burn efficiency. From an internet search. I also think it increases the spark due to the larger gap requiring more voltage .

I will agree with you on this topic. It may not be a hotter spark with a large spark gap, but it is a longer in length spark for ignition. I remember when I was into model t fords, that it was discussed to get a hotter spark by increasing the spark gap from .25 to .30. The improvement was to go from a 6 volt dc to up to a 21 v ac the magneto. The car always ran better off of the magneto than on the battery, so the long spark theory I feel is correct. Thanks Paul

Magneto spark these days is generally preferred for high speed engines as it creates a higher voltage / amperage spark where the battery and coil (kettering) system is prefered for slower running engines.

Tony 

I have 3 29s, 2 running and one not running. One car responded very well to the 18 degree advancement as suggested by Bill Barker some years ago. The other car was happier at about 15 degrees. You will have to play around with where your car runs best.