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I have a 1962 gmc with a 261 and it has the the 261 carb(larger throat size) would this be the dreaded Rochester B? It has no ID tag.

If you really have a 261 (would be odd in a 62 gmc), very good chance the carb is a "B." There are instructions on the board for posting pictures. That would tell us for sure.

Does it run ok? The B probably deserves most of the criticism thrown at it, but there are also countless millions of them still working fine.

Here it is:

Model B

Don't the Canadian GMC's run Chevy engines? If it's not the original engine it could be a transplant from a "Pontiac" that would probably be a bolt-in swap up there in ice cube land!
Jerry

That is the style Rochester that was used on later 235s/261s (with an air cleaner bolt on the top of the carb).

"Dreaded B?" - I think that later castings was not so prone to leaks between top/bottom of the carb (compared to earlier Rochester B/BC carbs).

Yes, the 261 was used on small Canadian GMC trucks starting in 1954. It was probably used on trucks through 62/63 (whenever 261 production ended in Canada).

Post the serial number (code) pressed into the block rearward of where the distributor goes into the block. Someone here might know the Canadian codes?

This is the original engine block number matches ID tag, I have not seen it run yet ,engine had a major failure before I bought it. Engine is now rebuilt and was looking for a carb kit.

I wouldn't worry about a Rochester B. I have one on my truck and it gives me great service.

Isn't the 261-sized "B" a pretty unique critter?

Yes, "unique" to the 261 engine

The 261 Rochester B had a larger venturi throat inner diameter and a larger throttle body inner diameter (compared to the 235 Rochester B).

It looks like 1958-1963 261 carb specs were the same but the air cleaner attachment might have changed in 1960?

Maybe someone knows when the air cleaner attachment changed?

The 1954-1959 261 Rochester carb model number was 7005140
The 1960-1963 261 Rochester carb model number was 7015143