If you use a single carburetor, you MUST replace the intake with a single carburetor intake. You CANNOT blank off one carb of a dual carb intake successfully.
As far as the Rochester versus Carter question, I prefer Carter, but I am not in England, and no offense meant, have no desire to visit unless someone builds a highway
With your uprated engine, you probably can use dual carbs successfully. But whether you use Carter or Rochester, THEY MUST BE EXACTLY THE SAME BY IDENTIFICATION NUMBER! If they are not, you are whistling in the wind.
Due to the port configuration of the 235, dual carbs are not ideal; triple carbs are ideal, but you need three smaller carbs. Or you need an IR style intake manifold. With an IR style, I would suggest three Carter type YH carbs. Forget the original Corvette units, as they are now contructed from verypricium.
Instead, three from mid-1950's Dearborn marine are somewhat available, and much less pricey than the Corvette versions.
If you were to use a triple manifold with the plenum design, the Carter 938S that Jerry mentioned in an earlier post will work well.
If you plan to stay with the duals, my first choice would be a pair of Carter type W-1 574s from a Chevrolet 216; which will require modification to the carburetor footprint on the intake, as the center-to-center bolt spacing is 2 11/16 inch instead of the 2 15/16 inch of the 235 carbs. These are manual power system, and will be MUCH easier to tune than either the Carter type YF or the Rochester. If you are set on 2 Carter type YF, then a pair of the YF replacements for the 216 NOT the 235.
Should you go with a single carb, I would suggest either a Zenith type 228 from an IHC or GMC 248 engine; or if you are looking for maximum power from a single barrel, then one from a GMC 270 engine.
And much as I dearly love (
) the Rochesters (read sarcasm), and assuming they are EXACTLY the same by tag number, I would try to find out why they are not working. Note my comment about the manual power system on the Carter W-1. One of the issues enthusiasts face when adding a big camshaft is the vacuum (which controls the power valve(s) on the Rochesters, will be different than with a stock camshaft, thus the power valve may always be open causing a very rich condition.
Also, read the thread by Jon G. on Rochester B power valve issues (stuck actuator valve, warped bodies, etc.).
As to the Pinto Webers: while others on this board seem to like these; I tried new ones 25 years ago when I could buy them new for $5.00 each!!!! Both Carter and Holley were trying to purge their inventory of these. At the time, I was unable to make one (or two) work as well as a single very worn original Rochester B that I restored. And even though I could buy them at $5.00, I completely gave up on them. There were more than a thousand available at the time.
I cannot in good conscience recommend these units due to the experience I had with them.
Jon.
