Sizing IR Carbs

[Rob R]

For reference:

[MadBill]

Interesting collectors...

[chimpvalet]

Modok, thanks for your patience in advising how to take up the issue in Pipemax. I took a look since my question was posted and see the application staring me in the face .

[mk e]

In How to Build Horsepower; Vol. 2, David Vizard gave an IR sizing formula that determines the ideal choke size, which he says should be 72-80% of the butterfly diameter, preferably the latter: choke in mm = √ (CV x RPM/2600), where CV is cylinder volume in cc and RPM is that of peak power.

I'm pretty sure that is...well....probably just a very general guideline and the part about getting it runner and then trying larger to see what happens is probably where the magic happens

[Belgian1979]

Yeah, I didn't say 350 c.i., I said SBC.

BTW, for a 377" 7,000 RPM engine, DV's IR sizing formula comes up with 57 mm carbs. (But of course GM didn't have a lot of sizing choices short of building their own carbs..)

I think I see where this comes from. You're saying 57mm bore size, not choke/venture size ...

Okay, my fault. In an EFI you wouldn't have a choke/venturi. The bore is roughly equal (or lager) than the choke of a carb. So yes, 45-48 mm chokes and whatever bore size that accommodates it I guess.