Need Some Help With A Rapping Sound

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Aug 9, 2006 | 07:36 AM

73 red vette

Thread Starter

Racer

Joined: Mar 2005

Posts: 445

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From: SAN DIEGO(SANTEE) CA.

Need Some Help With A Rapping Sound

OK, here goes. My 78 L82 stock original engine fas a loud rapping sound once it warms up and you get up to speed. It's not like a rod bearing knock but just a rapping sound.
I was wondering if it could be a cam bearing or if it's a lifter stuck and/or a bent pushrod. It started some time ago and hasn't got any worse it just makes the rapping sound

and gets louder the faster as speed increases.
been trying to figure this out for a year now and have know idea what it could be.
TIA guys

Aug 9, 2006 | 07:50 AM

wnmech

Drifting

Joined: Jun 2005

Posts: 1,523

Likes: 1

From: grand prairie texas

If it were me if the oil pressure is good I would pull the valve cover if you can identify which side the noise is comming from and check the rocker arms to see if any of them has excessive looseness. If you find one loose check the rocker and the push rod to eliminate them. Of course you are going to have to rotate the engine to make sure the rocker arms that you are checking that the valve is in the closed position. Good luck

Aug 9, 2006 | 08:42 AM

73 red vette

Thread Starter

Racer

Joined: Mar 2005

Posts: 445

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From: SAN DIEGO(SANTEE) CA.

Quote:

Originally Posted by wnmech

Thanks wn, I 'll try that this weekend see what happens.

Rich

Aug 9, 2006 | 08:47 AM

SmokinBBC

Drifting

Joined: Mar 2006

Posts: 1,526

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From: Oak Ridge NC

Is it coming from the top or the bottom end...front of the engine or rear? Left side/right side?

If you think that you know the general vicinity of the noise, you can narrow down the possibilitites.

Aug 9, 2006 | 08:55 AM

ghoastrider1

Le Mans Master

Joined: May 2006

Posts: 7,708

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From: indy indiana

I know this sounds stupid,,,but...my buddy ask me to help finding (76 L82) a noise like yours...first time i ever saw it....the fuel pump was loose.Instead of the "cam arm" being worked,the whole pump was.I agree with the others...sounds like it might be a loose rocker hammering away.Your discription is rather vague,this is the best i can do. hope it helps

Aug 9, 2006 | 09:25 AM

73 red vette

Thread Starter

Racer

Joined: Mar 2005

Posts: 445

Likes: 0

From: SAN DIEGO(SANTEE) CA.

Quote:

Originally Posted by ghoastrider1

I know my description is vague, but it's the only way I can describe it. it seems to definitely be coming from the top, not the bottom. That's why i thought it might be a cam bearing, but it has never got worse just stays the same. I have never heard of a cam bearing going out or have no idea of what it would sound like if it did,It did start after it overheated and I drove it about 40 miles so I could get home, but it didn't start doing it til about 2-3 weeks after that. It does seem to have no power on the freeway when I take it out for a run.
thanks guys
I'll check out your suggestions and see what I find.

Aug 9, 2006 | 07:42 PM

sly vette

Safety Car

Joined: Oct 2005

Posts: 3,570

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From: Algonac Michigan

"It did start after it overheated and I drove it about 40 miles so I could get home, but it didn't start doing it til about 2-3 weeks after that. It does seem to have no power on the freeway when I take it out for a run."