The Stovebolt Site Forums The Shop Area Engine Shop Carb question

The Rochester b I have has 2holes in the bottom flange
1 ia round and the other is oval(drilled at an angle)

The gasket that came with the carb has a notches that expose the oval hole

Another gasket I have has notches that expose the round hole (that gasket does not fit as well)

Also my original carb insulator has no notches but the new ones online have notches to match the carb gasket.

How important are these notches and which one should be exposed?

This is a Rochester b on a 1954 235 engine

I am thinking this could be the cause of my short whistling burst at initial throttle.


Thanks
Rich

Ps the second gasket that does not fit as well is the one listed for the 235 engine. But so is the carb

My old 216 had notches in the insulator plate

Any advice is appreciated. I can remove the insulator and drill the notches I just need to know which hole to expose

not to hijack a thread, but does my 49 216 with carter carb need a insulator? It did not have one from PO? Ordered one from classic, but it appears to be way to thick to work. Ran fine without, just wanted to check.

Rich,

The notches in the gaskets and in the insulator are needed to allow a vacuum "lead" to a hole in the base of the carburetor (I do not know the correct term for this hole/port).

If you are not using a carburetor gasket, the notch in the insulator is necessary for the vacuum "lead" (the Shop Manuals do not suggest a need for a gasket above or below the insulator).

If you are using a gasket with the notch between the carburetor and the insulator, there is no need for a notch in the insulator (but a notch there is OK).

If you use a gasket between the base of the carburetor and the top of the insulator, that gasket must have the notch orientated in the correct direction (to match the hole in the base of the carburetor).

A carburetor gasket with no notches might be used below the insulator (between the insulator and the intake manifold), but it would also be OK to use a notched gasket (or no gasket) in that location.

Many people simply always use a gasket under the carburetor and often under the insulator (to avoid vacuum leaks).

aggie jon,

If someone removed the insulator sometime during the life of your engine, they would have had to change the carburetor mounting posts (to shorter posts).

Usually the insulator is about 3/4 inch thick and protects the carb form over heating causing vapor lock and other issues

You might not have an issue in the cooler temps but it will vapor lock and gag a lot in the hot weather especially if you idle a lot ...like in a parade

Now back to my question. Heat hole should be exposed and does the insulator need to be notched?

Tim
I have 2 ports on the bottom they are only about a 1/4 inch apart
Close enough that the different gaskets expose a different hole
I used the gasket that fit better
The cab squeals (just a short high pitched burst) only if I hit the throttle quickly form idle. It is associated with a short hesitation.
The engine also stumbles slightly at max rpm

Other than that it runs great and has good power to be honest I can live with the squeal but not the stumbling

Could all this be related to the same vacuum problem

As alway thanks for your advice it is always helpful

Rich

I replaced the gasket with the other gasket to revel the other hole and the squeal is gone. The carb still hesitates a little and of course leaks like every rochester b I have ever seen.

I might replace the rochester with my newly rebuilt YF that I got on line for 10 bucks and see if that works any better.

The truck has more power but still stumbles a little at high rpms. It also seems to miss a little at low idle (my 216 did that too)