The Stovebolt Site Forums The Shop Area Engine Shop spacer under carb

have a 48 gmc 1/2 ton with a 228 motor and 1 barrel carb, Rochester...had a 5/8 spacer between the carb and manifold, it broke in pieces, do I need the spacer?

yes, it's not a 'spacer' it's an insulator to prevent boiling the gas in the float bowl

Bill

You may want to talk with other stovebolters in your area to see if they are running this insulator. Climate in your area may not require it. If it does they are available from the usual vendors, if not just a gasket will do.

In your area, so north, I would use it. In the summer it helps keep the carb gas from percolating. In the winter, as long as your manifold heat flapper works, it will help prevent carb frost from a vacuum leak on the manifold. They are made of bakelite(a resin) now, not dense paper fiber.

It was put there for a reason

where can I get one, or can I make one, if so what material can I use to make one.

right here. http://www.oldchevytrucks.com/cart/index.asp?cat2=10336&path=1947+%2D+Early+1955+Truck+Parts%2FMechanical%2FFuel+System%2FMiscellaneous+Carburetor+Items

Mike,

Will that work on an earlier GMC? It won't work on a 216 or earlier (pre-1950) 235? I have earlier GMC carbs with the smaller bolt pattern.

earlier insulator

later insulator

Jim Carter insulator at your link

The other size from Jim Carter (but, I have a post 1954 270 GMC carb with the wider base).

i just posted the page so he knows where to get one. which one it is exactly i dont know.

Reproduction spacers/insulators are made from injection molded plastic and not bakelite as was original. For several years I worked with this material making piston rings for gas compressors which will swell ever so slightly assisting sealing ability. This is why gaskets are usually required that were not there in the first place.
Throttle rod length will probably also be an issue leaving it out.

A gasket was not specified on either side of the insulator - it was directly against the intake manifold and the carb.

I tried gaskets on both sides of my reproduction plastic insulator, but it raised the carb too high and as a result the throttle rod was too short.

I finally bought an original Bakelite insulator from another Stovebolter. It seals tightly and doesn't require gaskets.

QUESTION:
What is the difference between the early and late insulators that Tim showed? Is it the location of the vent for the power piston? Or do I just have a screwy carb that someone built from various parts?

The vent on my Rochester B carb ('54 235) is close to the mounting holes. The gasket that came with my NAPA carb rebuild kit has cut outs for the vent in the same location as my carb. But the reproduction plastic insulators that I bought - both early and late - have the cut out farther away from the mounting holes. The plastic insulator covers the vent. The Bakelite insulator that I bought from George also had the cut out as on the reproductions. I cut out a new vent on the Bakelite insulator. If I had cut out a new vent at the indented mold mark on the plastic insulator, I bet that the carb would have leaked near the edge - see first pic below.

> Vent locations: Left=Rebuild gasket; Right=Aftermarket insulator
> Power piston vent - similar to my carb

Thanks,

- Lonnie

the stud spacing on the manifold is different.

got lucky guys, my wife work in a place that makes cathaders, and deal with a lot of that kind of plastic, so they gave me a chunk and I made one, thanks for the help everybody...