Carb advise

[aboz]

I've got a 250 inline six from a 1970 Nova in my '63 stepside. I'm getting ready to install a Clifford water cooled intake manifold with a matching set of street headers. I'm replacing the old single barrel with a Holley 2 barrel. Is there a huge difference between the 350 cfm and the 500 cfm? At this point I care more about gas mileage than torque or horsepower. Will the 500cfm be a waste on the factory cam or just too much for my engine? Need advice quick.

[1Bad62Pro/Street]

Hey bud,
I called my dad and told him you may call. If you need an answer quick! He said he can help ya. I'm not up to date on 6 bangers. We have that one out of that 73 Nova in the shop, but is stock.
If you do find out let me know. I think it may be a little to much if ya wanna get fuel milage.

Thanks Bud,
I like to hear it with the new headers. What kinda headers are they?

[slepysal]

I am running a 2 BBL HOLLEY 350CFM
it came off of a ford van works great.
I would love a 390cfm 4bbl holley but can not adfford one

[1Bad62Pro/Street]

So you can run a 4 barrel on a 6 cylinder? I have seen a dodge swinger with a slant 6 with one on itan but it was built for drag racing. Man that car would run! Sounded wicked too!

[Corts60]

Here is a good formula for figuring out what CFM your carb should be:

Cubic inch Displacement X Max RPM
---------------------------------------------- = CFM
(3456)

[Eagar1]

If it is a progressive 2 barrel then that will give you better mileage over the single barrel or anything else because the primary barrel is smaller, (as long as you keep your foot out of it). But having the secondary is nice for passing and pulling hills.