Knock, knock

Well guys I tried a couple of things to try to find the knock in my coupe engine.

First of all I took the fan belt off, started it up, still knock.
Second with the fan belt off, I did what CT Jack suggested-that is use a rounded 1/4 inch wooden peg, took the timing pin out, put peg in hole and started engine. Pushed the pin against the timing gear as hard as I could with the engine running. Still the same knock.
Third attempt to try to find knock. My daughter who was a paramedic for a number of years gave me a used stethoscope. Took the metal end off the hoses, put the hoses against various parts of the running engine. Did all these checks on the carb side of engine. First place I tried was along the head-very little knock noise. Second was to run the hoses along the valve cover from front to back. A little knock noise. Third I run the hoses along the pan. Little noise up front be as I got toward the back of the pan, had a good knock noise.

So, does anyone have any other ideas? Am I missing something? What else should I do?
Could it still be the timing gear? Should I pull the cover off it?

Thanks for all your help so far.
 
Fred, use a long screwdriver or dowel/broom handle, at least 16" long, to listen to your lower end. With engine running, put one end of the stick next to your ear, the other along the top of the pan at front, middle, and back. Increase and decrease the engine speed at the carb as you do this. Do the same thing along the valve chamber and the head. I think the stick will give you a more accurate indication. It sounds like bearings, or maybe wrist pin or piston slap or even the rear thrust bearing clearance. The stick will talk to you. Your next move might be drop the pan and look at the rod bearings. After that, it gets more complicated, as you undoubtedly know. Call me if you want to talk.
 
WHN said:
Check the timing gear. Also try heavier oil. 20-50 works very well on older engines. 10-30 seems to me to be to light for 100 degrees.

Before you start tearing down the engine, try some inexpensive options.

Marvel Mystery Oil in your gas can help with valve noise.
Click to expand...

MM Oil in the gas helps with valve noise?? How does it do this? Never heard of such a thing!
 
40 Deluxe said:
MM Oil in the gas helps with valve noise?? How does it do this? Never heard of such a thing!
Click to expand...

I guess you haven't spent much time reading up on old gas engines.

Some people swear by it. Some people say it's snake oil. I happen to like using it.

I am entitled to my opinion whether you agree or not.
 
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40 Deluxe said:
MM Oil in the gas helps with valve noise?? How does it do this? Never heard of such a thing!
Click to expand...

Today's gas isn't like the better gas we had in the 60's and 70's, and MMO helps to lubricate the valve stems. Today's gas doesn't have much lubrication quality, and MMO helps. I started using it a few years ago, and I also think it helps.:)
 
WHN said:
I guess you haven't spent much time reading up on old gas engines.

Some people swear by it. Some people say it's snake oil. I happen to like using it.

I am entitled to my opinion whether you agree or not.
Click to expand...

I agree that MMO is good stuff. It's just that I don't think a few ounces dissolved in a tank of gas can have any effect on valve noise. Valve noise is caused by excessive tappet clearance or severely worn out valve guides, or maybe a broken spring. MMO is of no value in such cases.
 
The temporary engine in my 28 had a bad knock with the slightest acceleration. After I flushed out the block and radiator I got rid of the hot spot caused by the build up of crud in the rear of the water jacket, and that also got rid of the knock.

I still have a light tick, which I'm sure is a slightly collapsed piston skirt on #3 or #4. Of course this was also caused by the hot spot overheating the piston. Just gotta love all the problems cause by people running straight water. :mad:
 
Thanks Glenn. Maybe I had better get the old timing gasket and take off the cover and see what it is doing. Seems like I have gotten a lot of comments saying that is what it is so better give it a try.
 
If the knock was worse at the REAR of the engine I doubt it's the timing gear which is at the FRONT. JMO
Keep us updated.
Paul in CT
 
40 Deluxe said:
I agree that MMO is good stuff. It's just that I don't think a few ounces dissolved in a tank of gas can have any effect on valve noise. Valve noise is caused by excessive tappet clearance or severely worn out valve guides, or maybe a broken spring. MMO is of no value in such cases.
Click to expand...

I have first hand experience with engines that had noisy valve trains but were not worn out or in need of a rebuild. Correct oil weight, for engine condition, and additives can help and could extend engine life.

Slow or sticking valves, I believe, can be helped with MMO used in gas.

I fully understand there are a number of people who think of additives as worthless. I can say I have used both STP and MMO in older engines and the difference has been amazing. Not expensive. If it helps, what does someone have to loose?

I'm not talking about oil burning, no compression engines with burned valves.

I am talking about engines that have been sitting around for awhile, or not driven very much.

I learned many years ago that I didn't know everything, and there might be good ideas or other ways of doing things, that I was not aware of. Enjoy.
 
Just an update on this situation. Still have not found the knock.

Someone suggested testing the compression. I did it with the engine warm. The following is the test results: #1=79 lbs,#2=73 lbs, #3=79 lbs #4 = 78 lbs. Not knowing much about compression results but these amounts seem to me to be pretty good-better than my Huckster. So doesn't look like any one cylinder has a compression problem tied in to a sticking valve if that is what one would expect to find from this test.

I think the next thing I will do is check the valve lifters to see if they need adjusting. This would be the next easy thing to do at this time. Will keep you posted when I get to doing this job.
 
To update, this problem, I did get into adjusting the valves. I found most of the valves were within the expected setting EXCEPT for valve number 6. It showed a setting of .027. Way over the .013 recommenced. So got it reset to about .014 and put the rig back together again. Wow, it looks like it did the job. The old engine sounds like most old Model A engines without the annoying Knock-Knock it had before.

Thanks to all your suggestions it looks like we may have solved this problem. Now all I have to do is figure out where I have an exhaust leak.

Thanks again.
 
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