Thread: 383 S/b tapping noise

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Hey ya'll built a 383 stroker and everything seems fine. I have about 6k on it and it runs strong. It has had a tap thought since new that is bugging me. At about 2000 rpms it is loud enough to hear in the drivers compartment. I've adjusted the valves with no change. It is not a rod or main bearing knock, could be valve train but I'm not sure. Being that it's a stroker I did have a crank windage tray contact problem early on but I fixed that "I think" any ideas or simular experiences?

Do you hear it at all rpm's? Even while idling? Hydrolic or solid cam? Does it sound like it's coming from one side and not the other?

Just right around 2000-2500, It's a hydraulic cam and it seems to be comming from the passenger side...thanks for your reply

Hey Tex,
It seems to me you only have a few things to check by process of elimination. It's either a bad lifter, a bent push rod, or a bad rocker arm. There is a test you can do to see if the noise goes away by tightening one rocker at a time. If the noise stops you found your problem provided that the correct lash was set on all the lifters before you started. Chances are the one making the noise will get real quiet when you tighten her down. That's the one I would replace. Push rod and lifter.
I hope this helps you out.

Crusty

IT SHOULD BE EASY TO DETERMINE IF IT IS COMING FROM THE OIL PAN OR THE VALVE COVERS. BY USING A ROUND PEICE OF WOOD LIKE A SHORT (16") PEICE OF A BROOMSTICK(MOM'S FAVORITE), PRESS ONE END INTO YOUR EAR AND THE OTHER ON THE VALVE COVER OR OIL PAN. CLOSE YOUR EYES AND LISTEN CAREFULLY. SOMETIMES YOU CAN EVEN PINPOINT THE NOISEMAKER FROM OUTSIDE THE COVER! LET US KNOW HOW THE SEARCH WENT. GOOD LUCK AND I HOPE IT'S SOMETHIN' CHEAP.

don't rule out a cracked flexplate/flywheel if the car is an automatic........chevys are bad about breaking out around the hub and is barely visible.usually can be detected by wobble in flywheel or noisy starter engagement...[sounds just like a knock]Good Luck,Kenny

the 400 crank does not have the clearence that a 350 has and cam lifts over .370 (.50@the valve) might cause one or more of the lobes to touch the edge of your rods depending on lobe seperation. when listening with a stethascope the noise is strange because it doesn't seem to match the harmonics of the crank or the cam. might i add been there done that . Launiti recomends that you dont exceed .512 at 102 deg. lobe seperation unless you use a smaller base circle cam with rollers.

Originally posted by Flyingtexan
Hey ya'll built a 383 stroker and everything seems fine. I have about 6k on it and it runs strong. It has had a tap thought since new that is bugging me. At about 2000 rpms it is loud enough to hear in the drivers compartment. I've adjusted the valves with no change. It is not a rod or main bearing knock, could be valve train but I'm not sure. Being that it's a stroker I did have a crank windage tray contact problem early on but I fixed that "I think" any ideas or simular experiences?

Hey Tex
Just a thought, what kind of clearances did you have between your rods and block. Disconect one wire at a time and see if the noise quiets down. How about piston slap. I would do the lifter ajustment thing first. one at a time. It you put your finger on the rocker arm you might be able to feel it.
Rich

Check your exhaust system. The tapping could be exhaust coming out from around the headers where they meet the block or where they connect to the rest of the exhaust. I have seen this throw people off before. The other thing is a possible bad lifter. Hope this helps some.

Originally posted by IRON WILL
Check your exhaust system. The tapping could be exhaust coming out from around the headers where they meet the block or where they connect to the rest of the exhaust. I have seen this throw people off before. The other thing is a possible bad lifter. Hope this helps some.

Ditto on the exhaust leak. that happen to me once. Rich

I've been out from under the hood of cars for 30+ years, so if my suggestion is silly, please understand.

Back in 1970, I chased a knock in a 327 chevy for many months before I realized that the fuel pump push rod had a slight bend and wasn't staying seated. Anyway, you may have an electric fuel pump and this wouldn't even be applicable.

By the way, I'm getting back into cars ('34 Tudor Sedan) and I have enjoyed coming to this forum to browse.

Dan J

Originally posted by Dan J
I've been out from under the hood of cars for 30+ years, so if my suggestion is silly, please understand.

Back in 1970, I chased a knock in a 327 chevy for many months before I realized that the fuel pump push rod had a slight bend and wasn't staying seated. Anyway, you may have an electric fuel pump and this wouldn't even be applicable.

By the way, I'm getting back into cars ('34 Tudor Sedan) and I have enjoyed coming to this forum to browse.

Dan J

Hey dan That's not silly, I ran across that once myself. Noises can be tricky some times. Some times it the simplest things that cause the biggest problems. Rich

here's a quick way to check rockers. Pull the valve covers and just grab each rocker arm and wiggle it. the one that wiggles more than the rest is bad. Kinda unscientific, but it works.

Justin

It could be the mechanical fuel pump...also check that the spring
to the actuating arm is in tact...or it will not maintain contact with the lobe.

Try that broom stick trick (or a 3' length of heater hose) and get back to us with your findings!

Tom

I had a weird one like that when I worked at a chevy dealer, it turned out to be a bad valve guide causing the valve to " slap" the valve guide when closing. Check that by running the motor and use a large screw driver and put a side load on the valve spring and see if that stops the tapping noise.