The Stovebolt Site Forums The Shop Area Engine Shop Nuther Carb Question

was reading MarkT's dual carb question, got one of my own...

I have a Nicson dual intake for my GMC 270... It appears as though the base-bolt pattern of the intake studs to attach the carbs to the manifold DO NOT match my Rochester carbs??

Are the carburetor base patterns different on the Carter, Rochester, Zenith carbs???

Yes, there were different bolt spacings on early and late Chevy sixes and possibly GMC too. Also different throttle shaft orientations among the GMC engines.

Take a look at the thread title "Zenith physical carburetor sizes".

Reference is made to S.A.E. sizes.

There are other threads stating the S.A.E. sizes on Carter and Rochester.

Basically size 2 is 2 11/16 center to center; and size 3 is 2 and 15/16 center to center.

The above is true for Carter, Holley, Rochester, Stromberg, and Zenith.

Jon.

Nicson is indirectly giving you good advice: you want carburetors smaller than your Rochesters.

Panic, carbking, cletis... Really wanna make a go of the dual Nicson! What smaller carb do y'all recommend?

There are many different carbs that may be used successfully.

Your choice should depend on, in order:

(1) The amount and scope of engine modifications
(2) Your expertise with the carburetors of your choice
(3) Your budget

These articles may help you:

http://www.thecarburetorshop.com/Dual1barrelcarbs.htm

http://www.thecarburetorshop.com/Triple1barrels.htm

Personally, if it were mine, I would use Zeniths from either a G.M.C. 228 or G.M.C. 248, depending on the scope of engine modifications. I like to make my changes appear as if they COULD have been factory; and the Zeniths were original on the G.M.C. A detriment from your standpoint to using the Zeniths is that they are probably the high end cost-wise to what is available.

Jon.