The Stovebolt Site Forums The Shop Area Engine Shop Carb gaskets

I can not seem to find this info anywhere. Is a gasket needed both above and below the carburator insulator plate. If not both spots, where does it go?

Most people only put one between the carb and the insulator. Notice too, the little groove off to the side to feed the vacuum port.

Originally from the factory there was only the Bakelite spacer/insulator between the carb
and manifold. As Fred posted, some people feel uncomfortable with that. If you feel there
has to be one under the carb then it only makes sense that there should be on under the
insulator also.

DG

I've posted this before ...

As Denny noted, the Service Manual does not show any gaskets used between the carb / insulator / manifold. I use an original bakelite insulator between the carb and the manifold on my '54 235 and do not use any gaskets. Perfect seal; no leaks. I tried running 1/16" gaskets on both sides of the insulator, but they elevated the carb 1/8" above the factory level. This caused the accelerator rod to be 1/8" too short and would not open the throttle completely.

I don't know if reproduction plastic insulators would seal without gaskets.

Lonnie's last sentence is important. Some of the after-market insulators do not have the "slot" in them for the vacuum port on the base of the carburetor. A gasket with the vacuum port/hole cut-out is needed or the carburetor will not work properly.

Of course, someone with Denny's skills and equipment could machine the slot into a replacement insulator.

Here are insulators that have the correct slots in them.

Here are some more with the slots.

The aftermarket insulators are harder than my original insulator that I bought from a fellow Stovebolter. Seems like mine has coating that helps seal. It may just be varnish from years of use, but it helps the insulator seal perfectly.

The new plastic insulators also have a mold mark in them that reduces the contact surface. If you want to run an aftermarket insulator without gaskets, then I suggest lapping it with ~150g sandpaper attached to a flat surface to get it perfectly flat, even if you leave some of the mold mark.

I haven't seen any aftermarket insulators that do not have "dimples" or "slots". If there is no dimple, one can easily be cut into the plastic with a Dremmel or drill.

Useless info: I bought three aftermarket insulators for my 235 w/Rochester B. None would work. The port for the power piston on my carb is in a different location than the dimple on the insulators. The mold mark on the insulator prevented me from cutting a new dimple. (My port is like a 216, but the carb has the correct size throat) I had to cut a dimple in the bakalite insulator; no problem, works fine.