Originally Posted by tclederman
Jon,

Thanks for your opinion (I was hoping you would respond with opinion and advice).

What carburetor would you recommend using as a single carburetor on an original manifold of a 261 bored to around 270 ci (over bored .060") ?

1. With original 7.5 approximate compression ratio

2. With an "848" head from a 1960 235 - approximately 8.25 compression ratio

It would be nice if the carburetor is one that could be easily tuned/adjusted/jetted on a 261.

Thanks,

My recommendation would be either a single Stromberg or Zenith WITH the adjustable main metering jet in a S.A.E. size 3. Which one? This is where the homework comes in. Since you now have a 270, and G.M.C. built a 270 with Zenith carb; compare your engine to the original G.M.C. 270. Take a look at compression, cam specifications, and desired RPM. Now take a look at the internal venturi used on the 270. If your engine is a bit stronger, add 1 or 2 mm to the venturi. If your engine is a bit weaker, then subtract a mm.

Probably, you will end up with either a Zenith 228 size 12 or a Stromberg BXV size 3 with an internal venturi from 30~34 mm. The homework will tell you.

Jon.

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The most expensive carburetor is the wrong one you attempt to modify.
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