Please disregard my last post. I found a 1953 Corvette intake on Ebay, with good pictures. When I get the software up on my new computer (the old one died after 8 1/2 years) will post the picture on my website.
The reason I wanted the picture was to augment Jerry's comments with a good picture.
OK, dual carbs CAN be made to work on the 216/235/261 as many have found, but never as well as 3 carbs, and only somewhat better than 1 carb. Jerry, Joe, and others have mentioned the limitation of the cylinder head, so the real benefit of multiple carbs (and no internal engine work) is to improve the volumetric efficiency of the engine through a more equal A/F charge to each cylinder. BUT, the Chevrolet 216/235/261 has THREE intake ports; so with dual carbs one has TWO carbs feeding THREE ports; impossible to get exact equal A/F distribution with this setup.
Joe H. HAS made it work fairly well, but Joe is from a family of racing mechanics. He understands HOW to get power from an engine, AND he has the testing tools to tune the setup. His Dad is famous in the racing community. While I know part of the history of Joe's multiple carbs, it would be interesting to hear the full story of how he ended with the W-1's, and how "easy" it is to just put some carbs on the engine and gain power.
Try to find a picture of either the intake ports or the Corvette intake manifold. Chevrolet used 3 carbs on the Corvette because of the port design. Three carbs feeding three ports, all running simultaneously.
The choice of carbs is obviously up to you; but if there are ANY carbs available which can be placed on the engine and obtain perfect (or as near to perfect as can be had) A/F ratios across the range of vacuum and RPM without MAJOR and I do mean MAJOR modifications and tuning, I haven't found them. I suggest the Carter W-1 BECAUSE: (1) readily available, (2) engineering data readily available, (3) parts (other than the accelerator pump for the 684s) readily available, and (4) all of the preceding are relatively inexpensive. Holley, Stromberg, and Zenith all are also excellent choices, but fall short of the Carter W-1 in all 4 or the criteria in the preceding sentence. Rochester NEVER went after the aftermarket, so fall much further short in these criteria than Holley, Stromberg, and Zenith (notice alphabetic order). If you really WANT to use something else, think of these criteria.
Finally, the transmission change suggested in this thread by 52Carl is an excellent idea. I have not personally seen this modification; however, the very best "bang for the buck" on a automatic transmissioned 1964~1966 GTO is to swap out the 2-speed dogmatic transmission for the 3-speed TH-350. Bolt in swap and will lower ET in the quarter-mile by more than 1 full second! How much money would need to be spend on the engine to accomplish the same result? Have seen this done a few times, always with excellent results.
Jon.
