Tapping noise when hot

rpm2831

rpm2831

Junior Member
My coupe makes a tapping noise only when warmes up after several miles and only ditinctive when idling.I also hear less tapping noise at idle with the spark retarded.We checked all tappets and they all are set at correct clearance.It is a steady on time tapping noise.It doesn't affect the performance and I ran the car at 45 to 50 mph at long distances with no mechanical problems.It has a 1940 high compression head(police head and has a lot of power. Any ideas? Thanks, Ray in Duckroost.
 
Can you narrow down the area of concern by using an automotive stethoscope with a long probe?

I had a similar tapping when warm that went away at spark advance on a warm engine. We also thought it was valve or tappet. Turned out to be a gland ring left over in one of the four exhaust manifold openings (#3 as I remember).

Saved a bunch of time and effort.

The cheap Scope at Harbor Freight has a nice sond piece, but the ear pieces are a little non-ergonomic for longer term use.
 
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rpm2831 said:
My coupe makes a tapping noise only when warmes up after several miles and only ditinctive when idling.I also hear less tapping noise at idle with the spark retarded.We checked all tappets and they all are set at correct clearance.It is a steady on time tapping noise.It doesn't affect the performance and I ran the car at 45 to 50 mph at long distances with no mechanical problems.It has a 1940 high compression head(police head and has a lot of power. Any ideas? Thanks, Ray in Duckroost.
Click to expand...

Rods.
 
rpm2831 said:
My coupe makes a tapping noise only when warmes up after several miles and only ditinctive when idling.I also hear less tapping noise at idle with the spark retarded.We checked all tappets and they all are set at correct clearance.It is a steady on time tapping noise.It doesn't affect the performance and I ran the car at 45 to 50 mph at long distances with no mechanical problems.It has a 1940 high compression head(police head and has a lot of power. Any ideas? Thanks, Ray in Duckroost.
Click to expand...

If it changes with the spark it has to be a bearing, piston, wrist pin. Did you try shorting out each cylinder to see where the noise is.
Herm does bearings all the time, I would go with what he says.
 
I had a tapping noise and after worrying about it for while I found the crankshaft pulley nut was loose allowing the pulley to rattle. Dumb
Easy to check.
 
I had a clicking noise in my rebuilt engine. It turned out to be a generator pulley that had the two sides of it put together with 4 rivets. The rivets were not tight so it clicked when running.
 
Just helped a friend of mine with a light, metallic tapping noise. It went away when we shorted #3 cylinder. Turns out it was a piston slap. Apparently one of his pistons was fit too tight, it got hot, and warped itself. When we pulled #3, the piston was scored and discolored. The car probably would have run forever, but he had new pistons refit, we put it back together, and now it runs quiet.

If it is more of a woody-sounding knock, it could be the cam. I don't think that will be affected by shorting out the cylinders or by the spark. Otherwise, it could be all the above (rod, wrist pin, etc).
 
I'm reminded of Richard Bach's book "A Gift of Wings" that he wrote after "J.L. Seagull".

He talks at length about the buzzes, rings, grinds, and other general noises apparent in his F-84 while transiting Europe. He notes that pilots of the more advanced "F series" fighters would have called an emergency and put their jets down for the noises that Bach took in stride.

If my modern Ford made 1/10th the noises of my 81 year old Ford, they'd call in the engineers, programmers and designers to ferret out the problem.

Here we just post and see who else has experienced piston slap, loose big ends, loose pulley nuts, etc.

I certainly feel more in touch with the environment and mechanics of my 40 raging horses than I ever do with my new "quiet as a tomb" on wheels.
 
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