I have what seems to be a stock cam 2 bbl 351W without headers and want to put a 4 bbl carb on it. I have a new 750 cfm 4160 Holley and would like to know if this is too much carb for this engine. If it is too much what would be the max size I could go and have no problems?
It has automatic and I’m not sure about the gears.
With a vacuum secondary that is properly set up with the correct tension diaphram spring (the tightest spring in the bag)the 750 will be o-k. If you already have a 750 on hand, go with it. If you are buying a carb new, get something a little smaller. Like 600 or so. Realistically, around 500 cfm is all you’d need with this combo.
See the car in my avatar? At that time it had a 750 vacuum secondary on a 351c with 2 v heads, Performer intake, headers with dual 2 1/4", bigger than stock cam–but still mild. 750 was more than it needed. Using the tightest vacuum spring gave the best results. The tighter or stiffer the spring, the slower and less the vacuum secondaries open. Meaning the full extent of 750 cfm was more than the engine could digest. But it still ran pretty good. So if ya got it go with it, otherwise choose what will be optimal for your application.
i took the 750 off my warmed 351C 4V as it was too big unless I wanted to drive above 2000rpm all day. All the experts said it would work but none of them could get it to function without bogging down, even with stronger springs. Swapped on a 600 and it was fine. I also learnt a lot about using a spacer on a dual plane manifold to get the fuel velocities up and improve bottom end on a 4V
For a stock 351W with auto, I would stick with a 600 or 670 street avenger on dual plane manifold
I have a Holley that came off of a 390 S code. I might try rebuilding that and see how it works.
I had a 750 Holley 4160 vacuum secondary on a 400 and it was too much carb for that. I changed over to a 600 Holley 4160 vacuum secondary and it sorted out all my idle and low rpm response issues.
The engine doesn’t spin up quite as fast, but the gained torque from a better tune more than made up for it. That engine is a 351M/400, so high rpm isn’t in their design anyway, but it will spin up to 5000 rpm no problem with that 600.
Yep, the key is the dual plane manifold. I ran a 750 for a while and then switched to a 600 on the same manifold and driveability improved. But then again, I’m not a mad carb scientist either.
My 70 has a 351 Cleveland 2 bbl and I went w/ a 600 CFM carb downsizing from the 750 that was on it when I bought the car. It runs much better with the 600.
I figured the 750 would be too big but thought I’d ask anyway to be sure. It looks like it’ll be a 600cfm because I have to have a smooth running car.
I have one of those on BetaCat (almost stock 351C-4V, auto) and it absolutely loves it!