C2 GM #3969835 Carb/Intake Heat Shield

[Paul L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

Then I feel rather silly and will have an NOS ...835 shield on EBay in the near future. I'm committed to that purchase. But the BB application does explain the potential fitment problems I mentioned earlier. Live and learn!

[Joe L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

Paul-----

That's why the 3969835 insulator was dropped from the Corvette P&A Catalog after 1970 (and, incidentally, fooled me into not checking further into the availablility/other applications of the 3969835. Since there were no actual Corvette applications for it, it was dropped.

However, the small block, Holley insulators that I metioned, which WERE used for some Corvette LT-1 applications, DID remain in the Corvette P&A Catalog for years.

Somehow the conclusion was drawn that because the 3969835 was for a Holley flange, then it was the right one for all Holley-equipped engines. That's not the way it is, though. The shield is configured to fit the particular manifold that it's intended for.

[Jack W.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

Joe, as always your depth of knowledge is appreciated - Paul, myself and some other folks on the forum where Paul and I first spoke about this are highly interested in this very topic - so just to make sure I understand you,

GM #3969835: was designed for the LS-7 (454 ci that never was) as well as 1970 Chevelles with LS-6 and L-78 (Doc Re has no need to repro this item, I would guess)

GM #3972156 (later, #3999198): was designed for the 1970 LT-1 350 ci / 370 hp
(Doc Re repro pn# 3726142 for the 70 LT-1, if I am not mistaken, and pn# 3726123 as repro for the 71-72 LT-1 350 ci / 330 hp heat shield). WHAT/Which is what we (those with a SB (327) 350 & up hp C2) need from the Dr, if we want a heat shield that will fit our manifolds?

GM #3969837 (later, GM #10147945): spread-bore / Q-jet piece for John's IROC; Note that Doc also lists a heat shield for a 1970 300, 350 and 390 hp application, pn# 3426140, those are the Roch Q-jets, so that shield is the pick if you have a 1970 in the 300, 350 or 390 configuration?.

sorry to belabor this, I just want to understand your advice as it might apply to my 65 L-76, as well as help Paul confirm his needs as well.

I hope I am not violating site policy (or getting the DR. mad) by referring to the page from the old Doc Re catalog that these items appear on:

http://www.docrebuild.com/dr-r-web/CARB-KITS.PDF

[Paul L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

This is indeed getting confusing. Here is the #3969835 NOS heat shield I purchased. It is identical to the #3726142 in Dr. Rebuild's catalogue: for use on an LT-1. Help!!

[Joe L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

Jack-----

Yes, the GM #3969835 is a Holley flange insulator designed for certain big block manifolds. Since it was never used on a Corvette, I don't think that Dr. Rebuild has it available.

The GM #3972156 was designed for use on 1970 Corvettes with LT-1 and NA-9 (EEC). As far as I know it was not used for 1971 Corvettes with LT-1. If it was, then it must have been on all since there was no NA-9 for 1971. I don't think that it was used on ANY, though. But, who knows, perhaps it was used in early PRODUCTION? Mostly, if not exclusively though, 1971 and all 72 Corvettes with LT-1 used a thick, insulating gasket with NO attached shield. I believe that this is the part that Dr. Rebuild supplies under his part number 376123. This is a 1/4" thick insulating gasket for a Holley flange but there is NO expansive, aluminum heat shield---it's just an insulating gasket. This piece was known as GM #3999259 and, perhaps, prior part numbers.

The GM #3972156 was discontinued from SERVICE in December, 1971 and replaced by the GM #3999198. At the moment, I don't know how these differ. It is POSSIBLE, although I have not confirmed it, that the 3999198 does not actually include an expansive heat shield.

The 3972156 and 3999198 were also used on other 70-72 era SHP small blocks with Holley carb used in Chevelles, Camaros, and Chevy IIs.

The GM #3972156/3999198 are the insulators which I believe that Dr. Rebuild sells under his number 3726123. This has the expansive aluminum heat shield and attached gasket. Although designed for use with the LT-1 style manifold, I believe that this insulator can be used with other small block Holley manifolds with little or no modification.

[Joe L.]

Correction

I erred in my posting. The Dr. Rebuild reproduction of the GM #3972156/3999198 which is the Holley flange insulator with expansive aluminum shield is his number 3726142.

The Dr. Rebuild reproduction of the 71-71 Holley flane insulating gasket with NO expansive alumiunum shield is his number 3726123.

[Joe L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

Paul-----

I have just confirmed that the 3999198 which replaced the 3972156 for SERVICE is an insulating gasket only; there is NO attached, expansive aluminum heat shield.

So, what we're talking about here is the difference between the 1970-only LT-1 with EEC insulator, GM #3972156, and the LS-7 with EEC insulator GM #3969835.

I do believe that there are some differences between these 2 insulators, but I don't know what they are. They may be subtle. I believe that the one that Dr. Rebuild supplies under his number 3726142 is the reproduction of the GM #3972176. As accurate as the drawings in his catalog are, it may not be able to discern the difference between the 3972176 and the 3969835.

Unfortunately, in my collection, I do not yet have an example of the GM #3972156.

[Paul L.]

Re: C2 GM #3969835 Carb/Intake Heat Shield

I have heard from the vendor (obviously looking in) and he has very kindly agreed to call off the purchase on the ...835 shield and return the funds I sent to him this morning. If anyone has an idea of what shield fits a 327 please e-mail me. I am completely lost.

[Jack W.]

Re: Correction

I will obtain the Doc Re pn# 3726142 (repro of GM #3972156/3999198) - the Holley flange insulator with expansive aluminum shield - and test fit it on a spare 65 SHP manifold with a spare 2818 Holley I have in my inventory, and report back on fitment for those who may be interested. (I am located relatively close to his operation in CT, and I have spoken with Geoffrey about this - he too is unable to state with certainty that it will fit my C2 application).

[Paul L.]

Re: Correction

Thanks Jack. Very much appreciated!