Thread: 4 barrel carb

Tweet

i have a 71 custom 10 with a built 350 in it, i don't know exactly what has been done to the engine for i just bought it, but i do know it has a big 4 barrel carter carb on it and i need better gas miliage and i heard that there is a plate you can buy to stop two of the valves from opening to pretty much make it a 2 barrel and i was wondering if this is true and where i could get one and if there is one if doing this to the carb is permanent or not and/or if there are any other ideas on how to get better gas miliage without just getting a 2 barrel or is that just my only option.

It has always, and I do mean always, been my experience that a 4bbl will get better gas mileage than a 2bbl; PROVIDED, you keep your big foot out of the back two barrels. I've ran both Rochester and Holley 2bbls and have always gotten poorer gas mileage than their 4bbl counterparts.

Rochester Quadrajets in particular get excellent gas mileage for 4bbl carbs. Holleys will also, especially the vacuum secondary 4160 models. As for Carters, the only one I've had experience with to any degree was a WCFB on my '57 Bel Air, and it always got horrible gas mileage no matter how I drove it. I don't think all Carters are like that, particularly AFBs and AVSs, but I don't have any experience to back it up.

I have personally never heard of a plate that blocks off two barrels of a 4bbl carb, although there is an adapter that will adapt a standard flange 4bbl to a standard flange 2bbl, but I can't imagine what good it could possibly serve. The best advice I could give you concerning improvement in your gas mileage would be to go very lightly on the gas pedal, and avoid opening the back two barrels. I will admit, it's kinda hard to do, knowing that you've got some extra punch under your foot if you want it. And, it's really hard when one of those noisy Honda Civics with a big wing and some stupid decals starts buzzing around you like a pissed-off bee. Man, they are just asking for all four barrels when they do that!

Randy

vurtok hit it dead, on... generally 4 barrel carbs will give you better gas mileage than 2bbl carbs. as long as your secondaries are vaccuum and you keep your foot out of it of course... mechanical secondaries destroy mileage... most i can tell you is that if you want to keep it so if you do open up your secondaries you dont eat up too much gas, would be to set it up so when you do open them up, that the butterflys dont open too far, which is adjustable on most carbs...