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Rochester B carb gasket question.
#1357723 Wed Apr 29 2020 11:32 AM
Joined: Sep 2011
Posts: 1,987
Lugnutz Offline OP
Shop Shark
In another post I showed the bottom of my Rochester B carburetor. It has two holes. I concluded that both holes should see manifold vacuum. That might NOT be correct. Here’s why.

I just examined two more carburetors that I have. Both of them have only one hole at the bottom. If you look carefully at the photos, you will see the 4 slot marks made by the gasket. Look at the gasket marks. Notice that the gasket slots do not line up with the hole in the bottom of carb. So, even the one hole carbs have the gasket covering the hole.

I know for a fact that one of the “one hole carbs” ran very well when I used it on my 250ci (presently in storage), yet the gasket blocks the hole. HRL and the ODSS gang at the 2018 ODSS Homecoming checked this one hole carb for vacuum advance while I was there and verified it was working.

Can anyone help me understand?

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Re: Rochester B carb gasket question.
Lugnutz #1357792 Wed Apr 29 2020 06:59 PM
Joined: Jun 2004
Posts: 8,202
Master Gabster
If that hole is blocked the carb will run extra rich. It allows vacuum to go to the power valve piston. Without it it will be on full rich all the time. Sure, it may run good but it will waste gas & cause excess carbon & dilute the oil. If the holes don't line up, cut a passage in the gasket to allow the vacuum from the intake manifold to reach the hole in the carb.

Last edited by Wrenchbender Ret.; Wed Apr 29 2020 07:06 PM.

They say money can't buy happiness. It can buy old Chevy trucks though. Same thing.

1956 Chevy 1/2-Ton Pickup

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