What jet size will be a choice for dual Rochester B carbs on a 235 Chevy? The ones I'm going to use have in the 70's size so I'm having to get new for them to match. Posted using the Full Custom H.A.M.B. App!
Just a guess but probably mid 50's. Hopefully someone with some 2-1 experience reads this.... A lot will depend on the air horns sealing so you have proper power circuit operation.
I haven't done the dual with rochesters but i suspect you can leave the stcok pill in it because of the way an in-line engine works. I do that combo with zeniths and they have an adjustable jet so it is hard to compare. I do have a selection of original rochester jets, pm me if you want to try a different setup and i might be able to help you out. I'd drive it first.
Stock jets range from 54 for a 59-60 PG, 57 for a 59-60 and some 61 Synchromesh, 56 for 61 PG and Syncromesh. These are 90 degree approach jets, they had an optional 2642 jet (60 degree approach), probably for altitude or the Mobile economy run. 54 sounds like a good start.
Thanks Hoop. That's what I was looking for. Didn't want to buy stock in the company buying all different sizes. Just a size to shoot for. I have done a bit of searching but couldn't find a definitive answer anywhere for this set-up. Thanks again to all that posted. Posted using the Full Custom H.A.M.B. App!
I hope I am doing playin' around with mine, time to get on with the rest of the truck. First off, I recommend getting a set of number drills and going through the carbs as per recommendations on this website:http://www.inliners.org/tech/tech4.html I got lucky and found a pair of 52 or maybe 50 jets that run fairly good. I have to admit I haven't been able to put many highway miles on yet. You can buy a pair of jets on ebay but this size jet is common in the Rochester two barrels so if you find one old 2-bbl you will have a pair of jets to work with. Make sure your carbs match. The base plate sizes should match and also the upper venture size should match. If they aren't real close you can find extra carbs for $5-$10. I've got several laying around you can have for cheap if you need to match them up better.
I have gotten to know these carbs way better than I wanted to but they are simple carbs. Well enough to know that 4 screws and a fuel line and the top of the carb is off in only a minute or two to change jets. I had 56 jets on the carbs but the plugs were black even though is ran kind of o.k. Keep us informed, lots of guys run pairs of Rochesters.
I've been doing this for a lot of years and didn't know how much I didn't know until I put an O2 sensor and digital readout to work tuning carbs. Now, I won't do anything more than adjust curb idle on a stock carb without one. They're magic for dual carbs, for modified engines. Set it up to reach into the cockpit and you can see cruise, acceleration and WOT in real time. Innovate makes a good setup, but there are others. With today's wonky ethanol polluted fuel, without an O2, you're just guessing. jack vines
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