[kellzey]

I'm building one by the way with 98mm P&Cs, 3.0L bottom end, early SC cylinder heads with 39mm intakes, single plug Electomotive Ingition, 3.6L oil pump, headers, and custom exhaust.

According to Bruce Anderson's weber sizing calculation.

Venturi size = 20 x square root of (Volume of one clunder in cc x RPM where engine reaches peak power/1000000)

It would seem that a lot depends on the cam you use.

For a 3.2 motor (short stroke)... one cylinder is 527cc.

Let's say you choose a 911S cam that has a peak HP rating at 6800 RPMs.

Plug this into Bruce's equation and you get a venturi size of 37.861 mm. Throttle bore (according to Bruce) should be 10 to 25% larger than the venturi size.

10% greater = 41.64
25% greater = 47.32

So a 46mm carb would work wonderfully!

If you went to a less-aggressive cam... let's say a late 964 cam with 6100RPM at max power, your throttle bores would be 39.44 and 44.8 respectively, so you could get away with the 40mm carbs.

My engine builder says there will be no problem running a 3.2 with 46mm carbs, even for street use. He builds them all the time.