3.2SS: Carrera or SC heads?

[YTNUKLR]

I've got these Carrera 3.2 heads sitting here about to be rebuilt for a 3.2SS. I will be using 46mm webers and DRCAMS DC60 or DC62 camshafts (and racing valve springs). I am strongly thinking about going twin-plug, with JE pistons in the 10.8:1 range. (This engine is going to use an SC crank, so 98mmx70.4mm).

BUT,

I've talked to a few people and they recommend I use the big-port 78-79 911SC heads instead of the Carrera 3.2 heads. I would like to run the 38/39/40 mm ports that they have...but if I already have 3.2 heads, why should I trade them in for the SC heads??

Thanks in advance
Scott

[Shuie]

Isnt the volume of the 3.2 heads different (bigger) than the SC heads? If so, you will obviously get a compression drop. Big port SC heads would be plenty big enough, but if you already have the Carrera heads.

Sorry Im not much help. I dont have any idea what I would do. Maybe tap them for MFI, run a real hot cam, and spin it as fast as possible . Oh, nevermind. you already have the 46mm carbs

[asphaltgambler]

My understanding is that the 3.2SC heads from '84-88 are the best flowing out there. In some cases (racing) you may want to actually reduce (narrow) the intake and exhaust ports for better high rpm airflow like in a short-stroke 3.2

[Henry Schmidt]

I believe the 3.0 are a better choice. The flange is longer on the SC heads and the ports can be modified to suit your needs. The ports on the 3.2 heads are so large that port velocity is negatively affected. The SC and 3.2 chambers CC the same and the valves are the same.
If you want MFI it is very difficult to machine Carrera (3.2) heads for the injector.