78 P.C. L-82 Strange Engine Noises

[Clem Z.]

Re: 78 P.C. L-82 Strange Engine Noises

the chevy shop manual tell you which valve to adjust at TDC #1 and TDC #6. you can use this if the valve clatter is in every cylinder and you can't hear which one you are adjusting with the engine running

[William C.]

Re: 78 P.C. L-82 Strange Engine Noises

YOu should also be able to "FEEL" a loose one when the engine is running at idle. Any chance some looney tunes put rhodes lifters in it? It usually takes a couple of thousandths of actual clearance to generate noise on a hydraulic cam, based on running solids on a hydraulic cam MANY years ago.

[Steven B.]

Re: 78 P.C. L-82 Strange Engine Noises

YOu should also be able to "FEEL" a loose one when the engine is running at idle. Any chance some looney tunes put rhodes lifters in it? It usually takes a couple of thousandths of actual clearance to generate noise on a hydraulic cam, based on running solids on a hydraulic cam MANY years ago.

Stu, Bill's method is what I have used since the car was new (late '76). When I drove on the street or track days I set them like that. When I autocrossed SCCA and NCCC I used to set them a thousandth or two loose on short courses. Bill is correct, you can feel them if they are loose.


Good Luck!

Steve

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

We did a complete adjustment on all the rockers using the book method (#1 and #6) as we did find them all slightly loose, that is we could easily turn the push rods and wiggle the rocker arm. Using the service manual method, we engaged them all 3/4 turn rather than the one full turn specified in the manual. Bottom line is that it runs smoother,but the diesel noise is still there. It had new (in appearance) rockers, screw in studs and adjusting nuts, along with push rod guide plates. The studs and guide plates were new to me.

Stu Fox

[Clem Z.]

Re: 78 P.C. L-82 Strange Engine Noises

did you check to make sure the rocker arms were not the self aligning type as they can not be used with guide plates

[Clem Z.]

Re: 78 P.C. L-82 Strange Engine Noises

picture showing the difference between self aligning and the standard rocker arm. http://www.cranecams.com/uploads/instructions/469e.pdf

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

Thanks for the heads up on the "self aligning" rockers. All looks correct for standard rockers.

Stu Fox

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

Thanks Dave for your insight. I did look at the holes when we did the adjustment and they were round with plenty of clearance.

Stu Fox

[Terry M.]

Re: 78 P.C. L-82 Strange Engine Noises

You don't suppose those furin car mechanics put the wrong cam in it? Any thing in the receipts to indicate what cam went in?

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

Terry;

Anything is possible I guess. The package of receipts we have from the shop does not break down the source or specifics of what parts were used. Our observation of the top deck valve train components seems to indicate they used standard replacement parts, but we can't even figure why they changed them at all in the first place on a car with such low mileage. The former owner is no help as he knows very little about the mechanics, and being naive may be the best indicator of why it was done. he's probably a good PI Attorney, but doesn't do to well with fraud.

Stu Fox

[Anthony P.]

Re: 78 P.C. L-82 Strange Engine Noises

Stu

Is this a four speed or auto? if Auto check for a cracked flywheel it will make a noise that is very similar to what you discribe, and will transfer through out the motor, just another idea, keep us posted,

Tony

[Joe C.]

Re: 78 P.C. L-82 Strange Engine Noises

Bill Clupper might be on to something:

http://www.rhoadslifters.com/Pages/Installation.html

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

Joe;

Thanks for the information on the Rhoads lifters. I will study it and try to figure if that may be what we're dealing with. My son's other 78 P.C. arrived from Phoenix last evening (another L-82, but w/4 speed and 1700 miles). We had them side by side in his garage today and the engine sounds are very different and he now agrees that the one is just not normal. He had a shop look at it and they say the front pump in the auto tranny has a leaky seal (?), so I suggested he have them drop it and at that time check the flex plate. His latest one is a great survivor and is most all original, and it truly sound like an L-82. I noticed the sound is much less when the engine is full warm.

Thanks again.

Stu Fox

[Stuart F.]

Re: 78 P.C. L-82 Strange Engine Noises

Dave;

Good tip. Thanks.

Stu Fox