1963 FI Exhaust Manifold Mystery - pic

[Bob M.]

I'm the second owner of a '63 fuel injection convertible which I purchased in 1965. The car had not been modified and all of the ignition shielding was intact. Recently, while looking at the driver's side (LH) exhaust manifold, I noticed that the casting number was 3797902 rather than 3797942 which I would have expected to find. Casting number 3797902 is the correct number for the right side and my car does in fact have a 902 on the right side.

I then realized that the alternator bracket had been ground off of the left side 902. The grinding is extremely well done, with a contour consistent with the curve of the runner and no obvious "grind marks" where the alternator mounting boss was removed. This is obviously not a home shop hack job. Also, the ground surface has a patina consistent with the rest of the manifold.

This car has a very short and mostly known history. Does anyone have a plausible explanation for this adaptation of a 902 manifold to the left side? Factory shortage of 942's? Dealer warranty repair? This occurrence is a mystery to me, but I strongly believe that the modified manifold is "correct for this car." Help me change my mind...

Left side and right side manifolds:

[John D.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Bob, I have seen this also but always thought it was done by a backyard restorer. In fact if I look hard enough I might have a 902/942 identicle to yours.
I am not saying it's original or not original as I don't know. I see no reason though for GM to have done that especially when they used many 1000's of the same exhaust manifold on passenger cars. But once again what do I know.
That's a really nice pass side exhaust manifold you have though.
Notice no one is jumping up to answer your question. JD

[E S.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Very early/pilot line car?
Was the '63 L84 the first application for the 942?
Prototype 942 that was mistakenly installed on production car?
Factory, or whomever, could have made this from a 901,and at least it would had LH cast onto it-but then they would have had to grind off the mount (to clear the air cleaner cannister), and also machine and install the hot air choke tube assy. I guess it saved a step to make it out of a 902 off a carbureted engine.
I agree-that's a nice looking 902 with FI

[Tom P.]

Re: 1963 FI Exhaust Manifold Mystery - pic

I can't give you an answer about your hybrid 902-942 manifold, and it does have the appearance of being originally cast this way (with the extra hole).
BUT, I can show and tell you this.
First, the 942 manifolds were never offered as a service replacement (they were only installed on production cars, both pass cars and Vettes). Only the 901, 902 and 563 were BOTH production AND service replacement manifolds. Since the 942 was not available as a service part, it could be "made" from a (3846)563 left hand manifold used ONLY in 64-65.
Back when these were still available from GM, I bought several to make as a "plain" manifold for both sides, OR, as a plain manifold on the opposite side from the side where the alt was mounted.
I used a die grinder and cutoff wheel to cut off the bulk of the bracket, then slowly and with lots of patience, ground off the rest, finish shaped it with attention to shaping the casting parting line, using a dull, worn out rotary file to duplicate the original cast finish, then blasting the heck out of the entire manifold to achieve an even finish.
Here are before and after pictures.
Also, notice the difference in an early 563 and late (service replacement) 563 version (different positioning of the casting numbers).










By using a 563 manifold to make a "plain" 942 type manifold, you don't end up with that extra, unsightly hole in the side, which you will have if a 901 or 902 manifold is used such as in the top picture posted by Bob.

Here is a real 942 manifold.

[Bob M.]

Judging an Aberration Such as Mystery 902

Very impressive work with the die grinder and, especially, rotary file, Tom.

A hypothetical question from someone just becoming aware of the world of judging: How would a situation like this be treated by judges? Would/could they "cut some slack" if they had no explanation for the left side 902, or would the points get whacked, no discussion? If the latter, that implies that we may have to modify our cars (i.e., acquire and install a 942 in this case) to make them "officially original" doesn't it? Is this in keeping with the spirit of the NCRS?

[Tom P.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Oh Bob, Bob, Bob!
I don't know.
I've been a member for a VERY long time (member 3491), and I've seen a lot of things that were fair and questionable and un fair and extremely unfair.
Over the years, there have been cars presented for judging with anomalies which the owner swore straight up and down and sideways was correct, original and even so much as the fact the owner was the original owner of the car, and the judges flat disallowed it. Then, several years down the road, it was determined after all that in fact the particular anomalie was genuine. Rare, but genuine. Consequently, the owner which had the particular anomalie on his car which was disallowed, had now become accepted by NCRS as a genuine factory, original part. BUUUUUUUUUT, too late for that poor guy, and because of the judges disallowing the item to be accepetd, the poor guy missed out on what COULD HAVE BEEN a top flight car.
Sooooooooooooo, where does this place your manifold for authenticity as a factory installed oddball, but genuine GM installed part? First of all, if another strange manifold such as yours has previously surfaced, and been accepted as the genuine article, they you should be fine. If no one has ever seen one, but if all the guru judges should examine it and determine that in fact it is a genuine odd ball GM manifold, then you may be OK. But, personally, I'd prepare myself for a rejection by the judges.
Should you remove it and replace it with a 942 manifold? IF IT REALLY APPEARS TO BE THE GENUINE ARTICLE, AND THERE APPEARS TO BE ZERO INDICATION THAT IS HAS BEEN MODIFIED SIMILAR TO WHAT I HAVE DONE TO THE 563 VERSION TO DUPLICATE A 942, I'D LEAVE IT!!! If it REALLY, REALLY appears to have been cast WITHOUT the remainder of the bracket for an alternator, then you probably have something worth retaining. If you, or someone, can come up with documentation or GM drawings which can verify this manifold, then have those in hand for judging. In the meantime, email Ken Kayser and/or John Hinkley for an opinion.
I have enlarged the picture, and it LOOKS real to me!

[Michael H.]

Re: 1963 FI Exhaust Manifold Mystery - pic

I'm the second owner of a '63 fuel injection convertible which I purchased in 1965. Left side and right side manifolds:

Bob, would it be possible to get a pic of the top side of this manifold, especially the area where the choke pipe would normally be on a non FI car?
Is that the original alternator mounting bracket?

Thanks

[Bob M.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Michael, I'll try to get a picture tomorrow. To confirm, you want a picture of the top of the right side 902, not the left side 902>942 in question, correct? I can also get a closeup of the area where the alternator bracket has been ground off the LH 902 if that is of any interest to you.

As far as I know, the alternator bracket is original. It's the only one I've had on the car since 1965.

For a little history on this car, see my thread on instrument cluster wiring harnesses posted earlier today. It contains a response to a question on how the IP was stolen. The engine and FI were out of the car at the time it was stripped.

Bob

[Michael H.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Michael, I'll try to get a picture tomorrow. To confirm, you want a picture of the top of the right side 902, not the left side 902>942 in question, correct? I can also get a closeup of the area where the alternator bracket has been ground off the LH 902 if that is of any interest to you.

As far as I know, the alternator bracket is original. It's the only one I've had on the car since 1965.

Thanks Bob. I was just curious about the area where a choke pipe would have been. Is that area rough cast on both the top of the manifold and the bottom where the lower end of the tube would come out?

I was curious about the alternator mounting bracket because it appears to be a later style. (mid 64 and later)

[Bob M.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Here are the pictures you requested, Michael.

1. Top of 902 manifold (Genuine GM overspray).
2. Choke tube boss top.
3. Choke tube boss bottom.
4. LH modified 902.

Bob

[Michael H.]

Re: 1963 FI Exhaust Manifold Mystery - pic

Here are the pictures you requested, Michael.

1. Top of 902 manifold (Genuine GM overspray).
2. Choke tube boss top.
3. Choke tube boss bottom.
4. LH modified 902.

Bob

Thanks Bob. The manifold appears to be genuine. (hard part to find)

The alternator mounting bracket appears to be 64-65 though. Note the location of the hole for the heater hose bracket.
The hole/screw would be close to centered between the large mounting bolts for 63 and early 64.
The hole was moved back, closer to the rear mounting bolt, for late 64 and 65.