Knock, knock

[Fred K-OR]

No it is not "knock, knock-whose there?" but rather where does this knock come from.

My 29 coupe has a knock! It seems like it knocks every time a piston fires. It is a kind of "hard" knock. It is there at an idle, still there when the engine speeds up a bit. Has just about the same knock with the spark lever either up or down. Do not seem to notices it when running at normal driving speeds. When I short out each cylinder, it does not change the knock. I have adjustable valves. It seems to be getting louder as time goes on. I run 10-30 oil in it and now days it is around 100 degrees here in good old rainy Oregon.

Questions-could it be a valve that needs adjusting? Is it a rod bearing? Is it a main bearing? Is it the timing gear? Is it the crank going back and forth? Or what??????

Any ideas would be appreciated. Don't have much experience with this type of thing.

[TerryH]

Mine was making a rythemic slight knocking sound that several Model A friends were stumped by. A short while later we found out.....the old fiber timing gear was stripping out and finally gave up the ghost.

[Fred K-OR]

Originally Posted by TerryH

Mine was making a rythemic slight knocking sound that several Model A friends were stumped by. A short while later we found out.....the old fiber timing gear was stripping out and finally gave up the ghost.

I put a new fiber timing gear in the rig a few hundred miles ago. Could be the problem because I did not know what I was doing at the time and maybe messed it up.

[Y-Blockhead]

Originally Posted by Fred K-OR

I put a new fiber timing gear in the rig a few hundred miles ago. Could be the problem because I did not know what I was doing at the time and maybe messed it up.

Fred, easy enough to pull the cover and have a look-see...

[WHN]

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. STP in oil will also help with flat tappet noise on engine with some mileage on it.

At this point it does sound like a timing gear. Enjoy.

[700rpm]

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Fred, put your timing pin in like you're timing the car, and turn the engine by hand. If the gear is loose you might feel a wobble. Did you torque that gear nut down tight, I mean really tight, and install that spring and plunger setup correctly in the timing gear cover?

The other suspects would be rods and mains. I hope for your sake that's not it. But it wouldn't be the end of the world. A lot of work to pull the engine, but Bill Barlow could pour new babbitt for you and have your block back to you in a few days.

I run 10-30 year round, and have for over 50 years, and have never had any adverse issues regardless of temps.

[Jacksonlll]

Dont rule out piston slap.

[1931 flamingo]

Take a LONG screwdriver, put the handle to your ear and start "probing" the block, etc. DISCONNECT (loosen) the fan belt FIRST ! ! !
You might be able to isolate the knock this way, FWIW
Paul in CT

[Fred K-OR]

Thanks guys for the ideas. When it cools down a bit around here, will have to try some of these ideas.

[Big hammer]

Shorting out number 2 and 3 at the same time, if knock goes away it's a loose center main

[Fred K-OR]

I tried this just now. Shorting out 2 & 3 makes the knock quieter but it does not go away. Thanks Big Hammer for the idea but doesn't seem to be that problem (I hope).

[CT Jack]

Seeing you changed the cam gear I would run a cam gear test. Take a 1/4" dia. wood dowel approx. 2 " long and round of one end so it looks like the timing pin used to time the distributor. Remove the timing pin and start the engine. Pay attention to the fan. Slowly insert the wood pin into the timing pin hole until it rubs against the turning timing gear. Apply a little inward force on the pin and note if the knock changes with the applied pin force. If it does this means either your timing gear nut is loose or the gear needs replacing. If you replace the gear I like to use a one piece fibre type.

[Fred K-OR]

Originally Posted by CT Jack

Seeing you changed the cam gear I would run a cam gear test. Take a 1/4" dia. wood dowel approx. 2 " long and round of one end so it looks like the timing pin used to time the distributor. Remove the timing pin and start the engine. Pay attention to the fan. Slowly insert the wood pin into the timing pin hole until it rubs against the turning timing gear. Apply a little inward force on the pin and note if the knock changes with the applied pin force. If it does this means either your timing gear nut is loose or the gear needs replacing. If you replace the gear I like to use a one piece fibre type.

Will have to try this in the A.M. It is possible that I did not get the gear nut on tight enough. If I remember, the nut was kind of messed up because someone before used a sharp thing to get it off and I could not get the wrench I bought on the nut.

[TerryH]

Fred....when my timing gear went bad, I had it replaced with an improved laminated type gear that should last much longer than the regular fiber type. For what it's worth, I had friends try and isolate the noise using long screwdrivers and other listening devices, and no one suspected the timing gear.....if your nut is bad, it is possible you did not get it fully tightened.

[CarlG]

Originally Posted by Fred K-OR

... If I remember, the nut was kind of messed up because someone before used a sharp thing to get it off and I could not get the wrench I bought on the nut.

If you buy a new nut, I would suggest getting the new style that uses a regular hex wrench to tighten it.

[WHN]

Originally Posted by Fred K-OR

Will have to try this in the A.M. It is possible that I did not get the gear nut on tight enough. If I remember, the nut was kind of messed up because someone before used a sharp thing to get it off and I could not get the wrench I bought on the nut.

Chisel was used to remove timing gear. I can't think of a Model A timing gear I have changed over the years that has not had chisel marks on it. Enjoy.

[Lona]

Some time ago, I had a similar noise we just could not isolate. Others also advised the likelyhood of a timing gear issue but all was fine when I took the cover off and inspected it. Quite by chance, I noticed a crack in the fan. Ran the engine with the belt off and the noise stopped. Replaced the fan blade, fixed the problem and avoided probable serious damage to myself and the car from a flying blade.

Glen

[jhowes]

I might suggest that if you use CT Jack's suggestion (which is a good one) unhook the fan belt first. Then it is out of the way and you are out of danger. Jack

[700rpm]

I used the nut the CarlG shows in post #15 on my recent engine rebuild, and I believe that for the first time ever I got that nut torqued adequately! I did it by clamping the camshaft in a vise and using a long breaker bar to get full power on the nut before I installed the cam in the block.

[Fred K-OR]

Thanks guys. Now all I need is some time to try some of these things. Will let you know how it works out once I get to it.