VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Clunkie, ##, Clunk.... clunk!!

Ok now I have a real concern.
I noticed the other day after I started my 31 coup up it had a inconsistent Clunking noise at idle? :eek:
It wasn't steady and it seemed to disappear once I gave it some gas or while driving? When I got home I was backing it up and I think I could hear it again slightly. The car seems to run OK.
I pulled it in the garage and got out the famous noise identifier (Broom stick). I placed it on both sides of the head and block and could only hear the valves clicking away. I could not hear it through the stick anywhere. I finally did transmit the noise when I placed the stick on the Intake manifold just above the carb.
I checked the valve springs, didn't see any of them broken. Guess I better open up the oil pan next to inspect in there. :(
I had it opened up when I first got the car last year. It doesn't have any sims left but the clearances on one I check was about .001 or .002. So i put it back together.
I confirmed oil flow to the valves I had a good return flow. I put a new gear driven oil pump on last year when I got the car. I do not know how to confirm the oil lines in the block for flow!

Any ideas from the discription I gave on my possible problem /s??????

Puzzled / concerned ...Shocks

I checked the plugs...........Dry no oil on any plugs did have some black carbon build up.

Oil level OK and clear.

Timing and plugs are correct; 18 degrees advanced, .040" plugs .018" on the points. Have not changed condenser yet!

TO DO LIST
1)Plan to open the oil pan up soon.

2) I was told to pull each plug off to see if anything would change noise wise. could be just piston slap!

3) Plan to idle the engine and put a screw driver in the valve springs. I have been told if the motor changes your springs are shot??


Shocks

At this point it sounds like a piston slap or a connecting rod. When you pull the pan check all of the rod clearances.....and while you are there you might as well check the main clearances also.

Thanks JYD, Would it help to isolate each cylinder with at idle. Could that help me identify the cylinder in question??? :(

How is the rod hooked to the piston itself. Is it a brass bushing or is it babbit too? I would guess a bushing considering it would be very hard to lubricate a babbit at that location.

Worried Shocks

The rod is attached to the piston with a piston pin, and the pin fits in a bushing within the piston.

If the noise goes away when you pull the spark plug wire it probably is a rod knocking. If the noise doesn't go away when you pull the spark plug wire, then it could be a main bearing knocking.

:( :( :( :( :(

JYD, thanks. If it is a rod or main. From what I have learned from readings other Chevy owners their issues I would bet its a rod. I read on this site some time ago that the rear main usually goes first. I would venture to say if its the main I would also have a major oil leaking problem there......"DON'T HAVE A LEAK THERE"

Looks like I will be taking the oil pan off in the next coming week /s

Thanks JYD ....Shocks

JYD........I started the old chevy up. After a few seconds you could hear a chunking sound grow and then fade away. By the time I got to the plugs I couldn't hear it. I started pulling plugs one at a time and when I pulled #3 plug I think it got better but not real sure it is very very faint if there at all.
I will try a cold start up tomorrow with #3 off to see if it clunks again. I will continue this proceedure until I prove it one way or the other.

Shocks