I'm not having much luck trying to locate a insulator gasket for one of the '71 LS6's. Original part # was 3989380, not sure what it is now. I think this insulator gasket is at least 3/16 th's thick.
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Re: Holley carburetor gasket
Warren,
If you can't find a correct gasket and are trying to remedy a heat soak problem get a piece of 3/16 or 1/4 inch phenolic and use a gasket as a pattern to make a spacer. I used a high temp RTV between the intake and phenolic spacer and then a regular thin gasket between the spacer and the carb.
Wayne -
Re: Holley carburetor gasket
The Dr. Rebuild catalog lists the Holley insulating gasket for '70-72 LT-1 as their PN 3726123 at $28. The 1971 AIM shows the LS-6 engine originally used insulator 3989390 which is the same as the '70-72 LT-1 part, but it was changed to 3999198 on AIM date 7/23/70 (start of production for '71).
That suggests the Dr. Rebuild part may be a valid substitute for the factory correct 3999198 insulator for the LS-6....Comment
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Re: Holley carburetor gasket
Thanks, Jack. I'll check with them.Comment
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Re: Holley carburetor gasket
Warren-----
Early 1971 LS-6 may have used the 3989390. Otherwise, the GM #3999198 was used. As I recall, the only difference between these gaskets is a slight difference in the configuration of the plenum cut-out. I think the corner radii may have been different.
Attached is a photo of an NOS GM #3999198 [not for sale]. It's still in an unopened package, so I didn't want to remove it for the photo. This insulator gasket is 1/4" thick and manufactured from some sort of dense, cellulosic fiber material. Either side is medium gray and all the edges are medium tan (apparently, the natural color of the cellulosic material). The GM #3999198 was discontinued without supercession in May, 1991.
I think the reproduction available from Dr. Rebuild is probably the best you're going to find, if it's not identical in every nuance to the original. Of course, very little of this piece can be seen when installed on the engine.In Appreciation of John HinckleyComment
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Re: Holley carburetor gasket
Joe,
That's exactly what I have on my white car. The orange car was missing, and had one of those metal heat shield with stapled thin gasket sandwiching the metal on both sides.
I knew that gasket was somewhat thick. Now I realize why I haven't had much luck locating one! Thanks.Comment
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