Carb size question??

[Jeff Alton]

Just curious about carb size.... 3.4, 10.5, twin plug, 1 5/8 headers, ge40ish cams..... How much power am I giving up using 40's instead of 46's?? Car is dual purpose street/track so drivability is important too. Or are the 40's just way too small??

Cheers

[Steve@Rennsport]

Jeff:

A 3.2 or 3.4 needs 46mm carbs. The venturi's can be sized for how you drive the car and what you like,.....

[camgrinder]

If you want to shift past 6500 rpms, I would say 40's are too small.

[Jeff Alton]

Very well then! 46's it is then!

Cheers

[Wayne 962]

40s are fine for a 3.0 or a stock 3.2 with carbs bolted on. Any increase in displacement beyond that, or a hotter cam will require the larger 46mm carbs...

-Wayne

[Henry Schmidt]

I agree with all the preceding posters. One thing to remember is that you can change the butterflies on you 40 to 44 or 46 and end up with what you need at a reasonable price.
When choosing a carburetor for track use it's important to remember that Porsche never used a 40mm carburetor on anything larger than a 2.0 and that engine used a 46 with 42 mm venturies.