70 LT-1 Carburetor Base Gasket

[George C.]

I have a 1970 LT-1 with a Holley 4150 (list 4555) carburetor and the stock Winters aluminum dual plane intake manifold.

I have been told the open carburetor gasket will allow a small leak across the divided plenum with the opening it creates under the carb baseplate and this leak will weaken the strong intake signal that a dual plane produces and could have an impact on jetting and idle.

What carburetor base gasket should I use; open or 4 hole?

[Joe L.]

Re: 70 LT-1 Carburetor Base Gasket

I have a 1970 LT-1 with a Holley 4150 (list 4555) carburetor and the stock Winters aluminum dual plane intake manifold.

I have been told the open carburetor gasket will allow a small leak across the divided plenum with the opening it creates under the carb baseplate and this leak will weaken the strong intake signal that a dual plane produces and could have an impact on jetting and idle.

What carburetor base gasket should I use; open or 4 hole?

George------


The original carb base gasket used for ALL LT-1's was an open plenum type. You MUST use this type. The LT-1 manifold carb flange will not support the 4 hole type gasket.

[Christopher K.]

Re: 70 LT-1 Carburetor Base Gasket

George,

This one is almost identical to the original which is impossible to find.

https://m.summitracing.com/parts/hly-108-12

May also solve any vacuum leaks

[Joe L.]

Re: 70 LT-1 Carburetor Base Gasket

George,

This one is almost identical to the original which is impossible to find.

https://m.summitracing.com/parts/hly-108-12

May also solve any vacuum leaks

Chris------


1970 LT-1 did not originally use a gasket like this. Non-EEC cars used only a thin, open plenum gasket. EEC used an aluminum shield with 2 attached thin gaskets.

[Christopher K.]

Re: 70 LT-1 Carburetor Base Gasket

Thanks Joe for the correction. I forgot the '70 Lt-1 was configured differently. Interesting difference between EEC vs Non-EEC.