C3: Holley 4150 intake gasket - Metal or no?

[Dan Pepper]

Does the Holley 4150 require the thin metal gasket on top of the composit material gasket on an '70 LT1 manifold? Or just the composit gasket?

TIA

[Joe L.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Dan-----

No metal baffle was used between carb gasket and carburetor on LT-1 applications.

[Dan Pepper]

Thanks, Joe. Greatly appreciated. *NM*

[Alan T.]

Re: C3: Holley 4150 intake gasket - Metal or no?

On this topic, I would like to ask, how thick should the Holley carb gasket be on a '70 LT-1 and where can you find the correct gasket? A while back I finally had to have the original carb on my '70 LT-1 rebuilt (don't think it had ever been off) and a thicker gasket (I believe it was the original) was on it than what the Corvette shop replaced it with. They replaced it with a fairly thin rubber gasket as I was told they could not locate the thicker original type. Thanks.

Alan

[Jeremy D.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Dr. Rebuild had the right one (so I was told) for my LT-1. I can't remember how thick it was, but it was thicker than a normal gasket. And, is your car a California car, because those DID have a metal "shield" between the carb & gasket & manifold. Something to do with dissipating heat or something...I know I've seen cars with them on. And you GOTTA have that correct gasket...the thin ones suck.

[Paul O.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Doc Rebuild does have a correct thickness gasket but the color is incorrect. There's is black in color and originals were a greenish-gray. I don"t have the P/N infront of me now but they due show up on ebay and swap meets. Paul

[Alan T.]

Re: C3: Holley 4150 intake gasket - Joe Lucia?

Doc Rebuild says he does not have one for 1970 LT-1 (but he does have them for '71-72 LT-1 and '70 LT-1 California). Does anybody know what is the difference in the carb gasket for a '70 LT-1 vs '71/'72 LT-1? Its hard for me to imagine what the difference could be - aren't they all for Holley 4150? Also, when trying to locate the correct carb gasket for a '70 LT-1, what is the part number? Is it a GM part number or a Holley number? Thanks.

Alan

[Joe L.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Alan-----

The carburetor gasket used for 1970 LT-1 without EEC was the same gasket as used for many earlier Holley 4 barrel applications since 1966. It was GM #3881847. That part was discontinued in April, 1973 and replaced by GM #682914. GM #682914 was discontinued in October, 1984. Dr. Rebuild does have a reproduction available of the gasket you seek.

1970 LT-1 with EEC used a special insulator type gasket ASSEMBLY. It was known as GM #3989390 and, later, GM #3999198. This consisted of an aluminum plate with an ATTACHED thin gasket, similar to the 3881847. The aluminum plate was designed to shield the carburetor fuel bowls from engine heat. It was not, at all, like the stainless steel baffle, either in configuration or function, used for many 1969 and earlier applications.

Dr. Rebuild also has available a reproduction of the above, too.

[Joe L.]

Addendum

I should have made clear, the GM #3881847 and, later, 682914, were THIN gaskets. They were not, at all, a thick, insulating type gasket.

[Alan T.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Joe, many thanks. One last question if I may, do you know if ALL 1970 LT-1s (non EEC) used the thin gasket like many earlier Holleys (the part numbers you mentioned) or is it possible sometime late in 1970 production they started using the thicker '71/'72 LT-1 gaskets? Mine is very late '70 production, next to last day, and the gasket I took off looked original, it was a thicker type. So just wondering if maybe late '70 LT-1s used the thicker type, as I would like to use the correct type gasket. Does an AIM maybe show that or other info you may have? Thanks again for your knowledgeable help as usual.

Alan

[Joe L.]

Re: C3: Holley 4150 intake gasket - Metal or no?

Alan-----

I have no information that would confirm that the 1971-style insulator gasket was used for late 1970 LT-1. If it was, it would mean that the 1971 choke assembly would also have to have been used (PRODUCTION choke assemblies included the thermostatic coil + rod) due to the thicker insulator gasket thickness. The problem there is that the 1971 choke assemblies were different than the 1970 choke assemblies. So, a 1971 choke assembly would not have been installable on a 1970.