Thump sound up front in engine, varies with speed

[daveymc29]

I have a pronounced hammering sound coming from the front of my engine. It was rebuilt with a weighted crank, balanced and inserted with full oiling system, touring cam (Model B profile as I understand it), Police head. I and my friends do not have the best hearing, but I have been noticing a pounding sound that appears to be getting louder. My friends were over and none could isolate where the sound was coming from and some doubted there was an unusual sound. I took a ride today and think it is getting louder by the day, so I got out the stethoscope and listened all around the engine. What I have found is that the noise is definitely there and if I put the scope on the timing pin it comes as a medium loud clicking sound. when I put the scope on the cam tensioner the sound is very pronounced and much louder. The car runs fine and I have not found any timing gear bits when I last changed oil, but that has been a while. Suggestions welcome. (Loose cam nut of broken teeth or tooth on the timing gear seem logical first choices to me. But what do I know?)

[BRENT in 10-uh-C]

Start with the camshaft plunger spring and migrate from there. Removing the timing gear side cover will allow access to this, and the condition of the timing gear.

[SeaSlugs]

How long ago was it rebuilt? I agree with brent

[Patrick L.]

I agree with starting at the timing gear. Do you know what kind of gear it is. You could remove and turn the timing pin around, insert in the hole, start engine and apply some pressure to the pin and see if it changes the noise.

Was there no noise in the front of the block on either side other than the timing cover ?

Did you try removing the belt just to see if it changes anything ?

[Tom Wesenberg]

I agree with Brent.
Full oiling means the cam is working harder to drive the oil pump, and if the spring isn't strong enough to keep the camshaft in place, it might be working itself forward at times, resulting in the noise you hear. Be sure to keep the distributor well oiled also.

[BILL WILLIAMSON]

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Dave,
Use a stethoscope with an open hose & hold it away a bit, helps LOCALIZE sounds.
Bro Bill

[burner31]

Have you eliminated the water pump the fan and the generator, as the source.

[James Rogers]

If it has an aluminum cam gear, they are a common source of knocks in the timing/plunger area.

[daveymc29]

Back when my friends were by, we took off the fan belt and then adjusted the valves. At that time we found on valve with a lot of clearance and one with very little. The builder must have had a bad day that day and the day he picked out my oil pump, its shaft broke as I exited the freeway. There is an adjusting screw on the front of the plunger housing just in front of the cam. Maybe all I need to do is tweak that a bit to put a tad more pressure on the front of the cam. I'll give that a go tomorrow and see what transpires. May get lucky. Engine is getting two years old, probably 3,000 miles + or -.

[Patrick L.]

I hope a bearing didn't get hurt when the pump shaft broke.

[Sunnybrook Farm]

Does the front crank shaft pulley clear the cross member all the way around?

[Tom Wesenberg]

I also have a cover with the cam plunger adjusting screw. Of course this is a home brew modification.

[johnneilson]

If the front cover has an adjusting screw instead of the spring I would expect to hear a knocking sound as the cam is moving forward and hitting the screw/plunger.

The idea is to keep the cam thrust to a minimum to reduce the timing fluctuations induced by the helical gears.

IMHO, the original oil pump drive is marginal at best for a full oiling system, by keeping the pressure down you can reduce the power required to drive the pump.

Best of Luck, John

[daveymc29]

Well here was the outcome. I warmer her up a bit and then listened to the timing pin with the stethoscope. Tick, tick tick. Listened to that adjusting screw that the boys for Oakdale put in there and it was hammering away. Took my half inch wrench to loosen the lock nut and found out that with the motor running, the fan is also going around. Stopped to bandage up that revelation, shut off the engine to prevent a repeat, then tightened the adjusting screw down a couple of turns and fired it back up. Silence from both the timing pin and the adjusting screw. Cleaned up the blood off the fender and all is good as new. The fan nick has even stopped bleeding, so I’m back in good shape and so is 29SMILE.

[62pan]

I painted my fan ends yellow so I wouldn't forget it was spinning. Glad to hear it was just a minor injury.

[hardtimes]

Originally Posted by daveymc29

I have a pronounced hammering sound coming from the front of my engine. It was rebuilt with a weighted crank, balanced and inserted with full oiling system, touring cam (Model B profile as I understand it), Police head. I and my friends do not have the best hearing, but I have been noticing a pounding sound that appears to be getting louder. My friends were over and none could isolate where the sound was coming from and some doubted there was an unusual sound. I took a ride today and think it is getting louder by the day, so I got out the stethoscope and listened all around the engine. What I have found is that the noise is definitely there and if I put the scope on the timing pin it comes as a medium loud clicking sound. when I put the scope on the cam tensioner the sound is very pronounced and much louder. The car runs fine and I have not found any timing gear bits when I last changed oil, but that has been a while. Suggestions welcome. (Loose cam nut of broken teeth or tooth on the timing gear seem logical first choices to me. But what do I know?)

Hey Davey,
Last year , I started up a new built B. Heard something like you are describing. I have a fancy alum finned timing cover plate...with outside adj screw/nut of brass. I had forgot to make a final fine adjustment. After adjusting and locking down this type cam adjustment device...no more noise. New McEachern bronze/steel gears..no noise. Good luck.
BTW...do not overtighten, leave a few thou clearance.

[Tom Wesenberg]

THUMP sound.............Oh, I thought you said TRUMP sound, and were hearing TWEET, TWEET.

[Chuck Sea/Tac]

I installed the set screw and jam nut on my car 4 or 5 years ago. It does require adjusting every now and again . I suppose hardness has some impact on how often. Be careful not to over tighten. I bottom out and back off a touch.

[Brentwood Bob]

Good outcome.