There is a tapping/knocking sound, coming as near as I can tell, from under the timing cover. Up high on the cover it is loudest, can still hear it to some degree down near crank. Not at all at fuel pump, Doesn't transfer to water pump. Hasn't given up yet at 4500 R's. No budget to replace it now anyway.

Found a double roller chain when we did heads cam etc. Felt ok, didn't change it. Maybe we should have?

Any ideas?

Dave H.
Houston, Quite Warm! TX

Well, you seem sure it is not the fuel pump, that was going to be my first response (and still is). Sometimes these noises are never diagnosed. I have a 350 in my 51 Chev that I built in 76 that has a knocking noise that has never changed. NO ONE can figure it out. It still runs strong, so why bother it? If yours doesn't change or get worse, maybe leave it alone?

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Tom Parsons

That is very hard to trouble shoot over a screen. An easier way to pin point it is to use a long screwing driver, better to have a wooden handle. Place its flat tip at various points. The vibrations will carry much like a stethiscope (sp). Then post a better explanation of the noise.

I had a similar problem last year with the 350 in my truck. Looked at everything and couldnt figure it out. Turned out to be a broken valvespring.

I have the same noise in my 350. Been there since I've owned it. No one can figure mine out either, she still runs strong. I have just learned to live with it. The fuel pump was the first thing I changed out, no change.
Mine seems to get very pronounced, once it's in gear and idling.
If you figure it out I'd be interested in knowing what you find.

Good luck!

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Bob
Merrimack, NH
{00==ss==00}
TC Gold Member #169
N.E. Chevelle & El Camino Assoc. #085
bob70@chevelles.com




[This message has been edited by Bob70 (edited 09-05-99).]

Guys,

Suggest changing fuel pump pushrod.

This is often overlooked & as DZAUTO & Bob70 says NO ONE can figure it out.

This may not solve your problems, but hopefully no one will give me a bunch of esoteric arguments about this being wrong w/o trying it.

I fixed mine.
Hope this helps.

I have seen bolts come loose on the cam gear and cause this type of noise. On one engine one of the bolts came out and took out the timing cover. How old is the rebuild?

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Jeff
Fort Dodge, Iowa
ACES #2814
Team Chevelle #21
www.dodgenet.com/~jmee/71chevss.html (http://www.dodgenet.com/~jmee/71chevss.html)
jmee@dodgenet.com

Hmm... I think I lock tighted the cam bolts. This was only about 3 months ago. I still think possibly chain slap or something, but there is a 406 sb in the future, and I don't want to tear into this one again (unless it chunks something).

Heck it COULD be a valve spring, but it runs well.

Thanks all!!!

Dave H.
Houston, TX

Are you sure you didn't lose a lifter? Had the same problem on my 65 283. Pull the valve cover and it's pretty easy to tell which one is talking to you. If you can tighten it a little and the tapping goes away for a few seconds then starts again you probably have a bad lifter.

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Chevy1999
Tucson, AZ