The Ford Barn - View Single Post - 1958 FE intake utilizing 4100 carburetor, vacuum leak at base

Brushwolf · 11-05-2023, 10:55 PM

Have a 1969 390 here topped with early 1958 machined chamber heads and matching 1958 4 barrel factory intake, but we are using a 1961 Ford 4100 carburetor in place of the Holley that would have been on a 1958.

Finally got it running last night and realized there is a vacuum leak at the base at the left front corner. This is because the corner of the 4100 carb base sticks out further than the horizontal carb mounting surface of the intake. I looked at a core 1960 and a core 1962 4100 carb on the shelf and all 3 carbs have this same issue where the base can not fully sealed to the early factory intake.

Comparing the 58 intake with an Edelbrock intake it is noticeable that the Edelbrock has a wider surface only at that left front corner which would alleviate this vacuum leak - except for the base gaskets that comes with the carb kit does not jut out to cover that area either. So basically it would leak at that corner even if used with the newer Edelbrock intake.

The outer perimeter of the base gasket does not extend to the outer perimeter of the 4100 carburetor base at only the left front corner where the 4100 has this little kickout at the left front corner of the base plate.

The 58 intake manifold casting for the carb base mounting surface does not extend out to the perimeter of the carb base at this corner either. So there is a triangular-shaped vacuum leak about the size of a pencil diameter in area. Sounds like a vacuum cleaner when running, unless plugged with a fingertip.

Has anyone run into this before and if so, how did you resolve it? Even if we swapped intakes it would still leak vaccum at this corner, although it would leak a lot less. Is there a special 4100 base gasket for this or do you have to make your own?

11-05-2023, 10:55 PM	#1
Brushwolf Member Join Date: Aug 2016 Location: Minnesota Posts: 90	1958 FE intake utilizing 4100 carburetor, vacuum leak at base Have a 1969 390 here topped with early 1958 machined chamber heads and matching 1958 4 barrel factory intake, but we are using a 1961 Ford 4100 carburetor in place of the Holley that would have been on a 1958. Finally got it running last night and realized there is a vacuum leak at the base at the left front corner. This is because the corner of the 4100 carb base sticks out further than the horizontal carb mounting surface of the intake. I looked at a core 1960 and a core 1962 4100 carb on the shelf and all 3 carbs have this same issue where the base can not fully sealed to the early factory intake. Comparing the 58 intake with an Edelbrock intake it is noticeable that the Edelbrock has a wider surface only at that left front corner which would alleviate this vacuum leak - except for the base gaskets that comes with the carb kit does not jut out to cover that area either. So basically it would leak at that corner even if used with the newer Edelbrock intake. The outer perimeter of the base gasket does not extend to the outer perimeter of the 4100 carburetor base at only the left front corner where the 4100 has this little kickout at the left front corner of the base plate. The 58 intake manifold casting for the carb base mounting surface does not extend out to the perimeter of the carb base at this corner either. So there is a triangular-shaped vacuum leak about the size of a pencil diameter in area. Sounds like a vacuum cleaner when running, unless plugged with a fingertip. Has anyone run into this before and if so, how did you resolve it? Even if we swapped intakes it would still leak vaccum at this corner, although it would leak a lot less. Is there a special 4100 base gasket for this or do you have to make your own?