I am building a tri-power setup for my SBC using Rochester 2G carbs (progressive linkage; 1 primary & 2x secondary). I have 3 early small-base carbs, all of which have the holes for an idle vent valve. One of them is missing the hardware that is attached to the top cover (the valve itself and the metal cover). Here is a question for you Rochester tri-power gurus: Do I need to retain the idle vent valve on the secondary carbs? Can I simply remove the hardware on both secondary carbs and plug the hole? FYI. I've done my homework on the conversion. I have bought the aluminum secondary bases (in fact, the entire kit) from Vintage Speed. I'm just not sure what to do with the idle vent. Thanks in advance.
I think what you're looking at is the bowl vent valve. I don't think you'd want plug them off as long as there's going to be fuel in the bowls. The bowl venting may help prevent fuel percolation on a hot engine after the engine is shut off. It may have been called an idle vent because it was meant to be slightly open at idle and lower speeds.
In any event, I just finished rebuilding a 2GC, and in my travels, I came across an outfit that had all that little stuff available (at a reasonable price, too!). If you can't find it, get back to me, as I think I can. (They even list the little rubber plug that goes in the sheet metal piece separately.)
I've noticed that there isn't a vent on factory tri-power carbs. That's what made me think they might not be necessary for the secondary carbs. I'm trying to convert the carbs I have (standard 2g) to copy the factory secondary units, so I want to get rid of as much unnecessary hardware as possible. Thanks. If I find I am missing something, I'll definitely reach out to you, too. Thanks for the offer. I can use all the help I can get. Poking around the internets, I came across HOTRODCARBS.COM. Is this the company you were using? They seem to have all of the little bits, too.
There is a site "Quadrajetparts.com" that has all kinds of little stuff. Don't mind the site name, they have stuff for all Rochester carburetors. They have the rubber part of the vent cover, but not the metal parts. You'll probably have to get them off a used carb. I have some I could send you, but I am in Florida until May and my stuff is in Minnesota. If you can wait that long, I can help you. Otherwise, I'm sure someone on here has them for a pittance or just shipping. It's called "The Power of the H.A.M.B.". As others have said, I don't think it's a good idea to just plug the vent.
Thanks for the links. I just acquired a bare '58 Pontiac tri power manifold and am starting the adventure of finding/modifying carbs.
I'm sure things have changed over the last 20 years, but back then, a guy I knew, who was "in the know" told me, "the most expensive thing you can buy is a bare '60's GM tri-power manifold".
So far the intake system is the most expensive single component on my build, other than the body and frame. I paid more for the unrestored intake and carbs than I did for the 350 short block, which was rebuild by the PO 5000 miles ago.
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