66 Big Block Valve Covers, Side pipe clues

[Tony J. Hurtado]

I am interested in whether all right side 1966 Corvette big block valve covers had the indentation to accommodate a/c compressor or was it just the a/c-equipted cars that had this valve cover? The car I am looking at has 4xxx serial number and no a/c (and no indentation on valve covers). Were a/c indented valve covers used on non-a/c cars in any part of production?

Also, what are some of the clues that the side exhaust are original on 1966 Corvette?

[Dave, NCRS#24235]

Re: 66 Big Block Valve Covers, Side pipe clues

According to Noland Adams book, the valve cover indentation for a-c bracket was not needed, and the covers were installed randomly on a-c and nona-c cars. My 66 has a-c - so I was interested. - Dave

[Ed S.]

Re: 66 Big Block Valve Covers, Side pipe clues

Tony,

The judging guide and technical manual has a pretty good list of clues that help identify a non-original sidepipe car, but here are the ones I remember off the top of my head:

1. Original construction fiberglass, unfilled, smooth rear exhaust valence panel 2. Absence of an exhaust pipe support at the transmission mount/frame x-mbr. 3. Untapped holes in the front of the frame x-member (undercar exhaust systems used these to attach the radio ground straps) 4. Lack of weatherstrip on the small triangular frame-to-body splash pans in the front fender area. (should be absent of any staple holes or signs of filled holes) 5. The fiberglass at the rear of the rocker panel area is notched on sidepipe cars 6.Look up underneath the rocker panel to determine if the original rocker panel mounting arms have been bent back out of the way, or have been shortened by other means during the addition of the sidepipes.

These points should help you begin the verification process regarding the authenticity of the sidepipes. I'm certain others can add to this list.

Good luck,

Ed

NCRS #13671

[John H.]

Another Sidepipe Clue

Tony - another possible clue to an original sidepipe car is a shim between the trans mount and the crossmember equal in thickness to the non-sidepipe exhaust hanger bracket (part of factory package to maintain design driveline angles).

John

[Scott Marzahl]

Re: Side pipe clues

Another side pipe clue is that there should not be any supports in the bird cage channels that are under the rocker panels. That channel should be open.

Scott

[Wayne W.]

Re: 66 Big Block Valve Covers, Side pipe clues

Many 66 BB cars without a/c had the indentions.

[Wayne M.]

Re: Another Sidepipe Clue

John --- I was thinking of that very spacer at the transmission mount the other day, when I removed my non-side-exhaust pipe hanger/clamp. It was 0.12" thick, so the trans yoke will sit at least 1/8" lower without a spacer on side exhaust cars.

Now here's my problem; the AIM (for '65) under N14, does not show this spacer. My '70 parts catalog shows it only for '69 w/side-mounted exhaust (exc.TH 400) [part Group 4.085, # 3949179]. Repop parts catalogs show it, but was it really installed on factory N14 cars ?

Maybe Joe L. can point me to the correct place in the GM parts book, if I'm missing something.

[Tom B.]

Re: Side pipe clues: The other 2 (66 JM)

7) in addition to the rear quarter panels that are trimmed for fit near the rear rocker molding, they are also smoothly cut to provide a 3 1/2" radius for exhaust pipe clearance, and 8) Look for evidence of rear muffler support brackets that attach to the frame. TBarr #24014

[Kieran A.]

Re: Another Sidepipe Clue

Wayne, I also looked at my 1967 roadster with sidepipes and did not see the spacer that is mentioned in the restoration catalogs.The car is apparently very original and the sidepipes can be verified with the tank sticker. I then looked in the assembly manual and as you mentioned saw no drawings that indicate the spacer being installed. I ordered one just to be on the safe side(only $5.00) since I plan to have the transmission serviced soon to correct a rear bearing problem. Any further information would be greatly appreciated. Thanks,Kieran.

[Wayne M.]

Re: Another Sidepipe Clue

Kieran --- Thanks for the observation; my post was based on speculation, as neither of my '65's were factory N14 cars. It was just a case where the NCRS Tech Guide, GM documents (AIM and Parts Cataloge), and the reproduction companies' catalogs don't equate.

If I was converting to side pipes, I'd probably add a spacer; but I question as to whether any '65 - '67 Corvette had one factory-installed. Responses from any other original cars out there ?

[Terry M.]

Re: Another Sidepipe Clue

Kieran,

I am far from knowledgeable on mid-years, but my understanding is that spacer under the trans mount is a 1969 only feature. I have to admit this makes little sense to me since the frames are basically the same and the spacer only takes up the thickness of the missing exhaust hanger that goes under the trans mount on cars with under chassis exhaust. If this spacer is needed on 1969, why not in the mid-years? I just don't know.

Terry

[Wayne M.]

Re: Another Sidepipe Clue

Kieran --- After reading Terry M's post, I checked the '65 NCRS Tech Guide and it does NOT mention the presence of a spacer, just the absence of the clamp, so I stand corrected. However, to avoid giving a "free ride" to those with an "owner-inspired" (added) spacer, perhaps the Tech Guide should add a note under "Mounting: Hangers and Clamps", as they have exhaustively (p.i.) covered all other evidence of side exhaust mods.

And, as I said before, if I wasn't having it judged, I'd add the spacer to maintain driveline angle and reduce any extra work on the driveshaft U-joints (which I believe mostly correct the engine off-set to the right at the front motor mounts).

[Kieran A.]

Re: Another Sidepipe Clue

Wayne and Terry, There is no mention of the spacer in the 1967 AIM and also no mention of it in the Chevrolet service manual. I will check for a part number later today but an sure Joe L. could find it (and its possible years of application) given his extensive knowledge/library. Thanks,Kieran

[Kieran A.]

Re: Another Sidepipe Clue

Wayne,Terry mentioned that the spacer for the transmission mounting support was used starting with the 1969 year. According to the parts book,section 4.085 lists this spacer for corvette with side mounted exhaust as #3949179 and lists the year of application as 1969 only. I also looked in section 3.708 in the exhaust section for a front exhaust pipe clamp but all these descriptions were for under car exhaust systems(at least as far as I can tell).Unless someone can add more to this discussion topic, I think Terry has the final verdict.Kieran.