Need some numbers help

[Mark Carlisle]

So I take my car to Tom Jumper Chevrolet in Atlanta because several people raved about a mechanic there. It wasn't running right so I thought it needed a tune up. A week later I call to see how the progress is going. They tell me it has the wrong heads. The casting number is correct but the date says early eighties. I don't have access to the car right now. I do have the books that came with the car. The previous owner who had it Bloomington Gold certified and Top Flighted has a two page list of all the parts/numbers/dates. For the heads it says:
Drivers' side: 3973487 (A111)
Pax side: 3973487 (B181)

The mechanic says he bore scoped the numbers on the heads under the valve covers and called GM. GM says heads come from early eighties. I have had the car three years and recently took out the spark plugs. All had the same gap but were a little dirty. I cleaned them and put them back in the car. Mechanic says the pistons are hitting the spark plugs and closing the gap. I wonder why this didn't happen in the previous years. I have only talked to the service advisor who stated, "We think it may be a high dollar forgery, but were not sure." I have not talked with the mechanic only the service advisor. Now this is a 1971 LT-1 that was able to make it past Bloomington Gold judges, NCRS judges, and I had an NCRS guy in San Diego assess the car and he found nothing wrong with it. Unfortunately, it has not been able to pass the scrutiny of Tom Jumper Chevrolet. Any help with these numbers would be greatly appreciated. This has turned from "please fix my car" to "now I have to defend the validity of my car."

[Joe L.]

Re: Need some numbers help

Mark-----

First of all, neither NCRS or NCCB judging processes involve "bore-scoping" any part of the engine to determine if internally visible "numbers" or components are correct. If the external configuration is correct, then the part is deemed to be correct as far as judging is concerned.

Second, you did not mention what head casting numbers that the "bore scoping" process conducted by the "Tom Jumper Chevrolet" technician revealed. If the numbers are the same as those you reported from the previous owners' information, then those heads are the correct casting number for your application and car. The dates also look to be correct, depending upon when your car and engine were originally built.

In addition, the GM #3973487 cylinder heads were not being produced in the 80s, so they couldn't have originated then.

If the numbers discerned in the "bore-scoping" process are OTHER THAN the numbers you reported above, let us know what they are and we may be able to tell you more. In terms of EXTERNAL configuration (which, as I say, is all that's usually checked in the judging process) there are many other heads which are identical to the original heads used for 1971 LT-1s, but which have different casting numbers and some elments of different internal configuration.

[Mark Carlisle]

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[Tom H.]

Re: Need some numbers help

The part # and date code will both be under the valve covers.

[Robert C.]

Re: 81' LT-1

Mark, What the heck is a chevy dealer doing scoping the heads on your car.On an LT-1, all you need to do is take off the oil cap to see the part#, date, on the drivers side head. On the heads,raised configuration on the front, looks like a little peaked house.
Believe me the NCRS judges didn't miss that much.And the casting date! No way! At Bloomington to? No way! Someone is getting their info wrong. Either you or that service guy doesn't know Jack .... I'd be getting someone who knows what he's looking at to go with you to check it out! Any way I'd get my car out of the before it turns into an 81'. It wouldn't be the first time that parts disappear off a valuable car taken buy a mechanic.

[Mark #28455]

look at the deck shape of the head

First, get your car out of there as fast as possible!

Early 70's vintage heads have a straight lateral side below the exhaust ports with one nickle sized semicircular "cutout" to clear the driver's side oil dipstick. Later 1970's and on "lightweight" head castings have a cutout between every two head bolts (between each cylinder making three large cutouts per side) it's really obvious, so it's easy to spot a 1980's vintage head casting!

How much did the dealership charge you for scoping the inside of your engine? Did you ask them to do it, or did they do it first, then tell you? You may need to talk to your regional service manager at GM.

Good luck,
Mark

[Dennis C.]

...Or the cops or your attorney... *NM*

[Mark Carlisle]

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[Dale S.]

Re: ...Or the cops or your attorney...

If the heads have been pulled, make sure you get your original heads back. I heard of parts swaper's more than once in the parts business over the years. Dealers don't do investigative work for free. Why are they scoping out your car, what is in it for them? Did you ask them to look inside the engine? Just thoughts. Dale

[Mark Carlisle]

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[Mark #28455]

plug indexing

If what they say is true - that somehow the pistons are closing the plug gap (this typically happens only on super high compression racing engines) you could probably solve the problem either by making sure you do not use an extended tip plug or by indexing the plugs for each chamber. Draw a line on the ceramic of the plug on the side where the ground electrode is (the little arm that the spark jumps to) buy plug gaskets of various thicknesses from a supplier like Moroso and then juggle the plugs or the gasket thicknesses for each cylinder until all the plug lines point up away from the pistons.

Like I said before, I doubt this is the case as only racing pistons with HUGE domes even get close to the plugs and you would know it as the engine would knock like crazy on any pump gas. So back to just getting the car out of there in one piece.

Good luck,
Mark

[Mark Carlisle]

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[Richard S.]

Re: plug indexing

Mark,
May I suggest you print this thread and have someone take it over to the dealer early on Monday morning with a note from you to the service manager asking him to call you on your cell phone....or you call him as soon as the dealership opens. Tell him in no uncertain terms, you want to clear up any misunderstanding right now. Good luck....

[Robert C.]

Re: Big Hoax.....

Mark, I don't know if I'd pick up the car or not. If it isn't what it WAS when you brought it in, I might consider going in to the dealer and taking a few pictures of the engine compartment(heads) and then leave the car and have your lawyer call them. If you take your car out of there, they'll say that the heads etc. were changed at another time.........etc.

[Dave F.]

Moral to this story

IMHO, the LAST place to take a vintage Corvette is a Chevy dealer. If a diagnostic or repair need falls outside of my realm of expertise, the FIRST place to seek advice is THIS forum unless you have a bonified specialist in your area. With few exceptions, the bulk of mechanics that work at any dealership are kids who are paying back their schooling to the dealers they work for, and with that you get the qualities of "on the job training" performed on your vehicle. I agree with the advice given regarding "photo documenting" your car as it sits at the dealership now, then removing it asap!!