Replacing a Autolite 4100 w/1.12 venturis for a 4100 w/1.08's, but am puzzled that the carb provider sent me a carb/intake gasket with the single square bore opening instead of one with 4 round holes matching the one I destroyed when removing the old carb.

This will make a difference in where and how vacuum signals are detected and function, right? It would make a gap between the carb and the 1/2" spacer effectively joining all the bores and creating a place for fuel to collect or be disrupted, right?

Looking at the top of the "B" manifold, this would be a problem even without the spacer, rights?

Sorry for such an elemental question, but sometime it helps to a) get a confirming answer, and b) just think out loud to someone other than my shop dog.

Cheers.. Brian

Cylinder Index = 84

Current Experiment = `57 Tbird, Grand Rapids, Michigan

Y blocks seem to like the 4 holes better than the one open gasket. I prefer to make my own carb base gaskets for the Autolite as the over the counter ones are cut too close to the edge and can leak.



The base of the Autolite 4100 has a bridged base not a flat base as the Holleys, a vacuum leak will occur at the front of the carb between the two idle mixture screws if you do not use a flat base plate under the carb. The base of the carb and manifold base are near same dimensions and after the gasket gets damp it will suck inward. I use a 1" four holed phenolic spacer that is least as large as the 4100's base. Without a spacer your butterflies maybe to large for the holes in the B manifold and could stick. Yblocks seem to like spacers anyway. With spacers the holes are usually large enough for the butterflies to clear easily.



On Teds intake and carb testings the addition of a spacer really did shine.