carrera 3.0 heads versus 81 sc heads

[mb911]

I have a chance at some carrera 3.0 euro heads and was wondering if there is any benifit to my application of my 3.0 that is turbocharged?? Is the head stud spacing the same?? Thanks

[Bill Verburg]

930/02 C3 heads are the same as 930/03 RoW '78-79 SC, 930/04 US '78-79 SC, 930/05 Jpn. '78-79 SC, 930/06 Ca. '78-79 SC

In '80 SC Intake ports were reduced in size to speed intake air velocity

930/50 RoW '75-77 turbo used even smaller intake ports but bigger exhaust ports

930/60 RoW '78-79 turbo used the small intake ports and smaller exhaust ports

[mb911]

so from what porsche did the smaller the intake port that I currently have may be a benefit?????

[Bill Verburg]

Smaller ports will speed up gas flow, this has a tendancy to give better throttle response, it may have an effect on emissions and probably fual milage as well.

My only experience w/ different port sizes comes from racing motorcycles, we had small port heads for shorter , tighter circuits and big port heads for longer faster circuits. Pipes and tuning were also changed of course.

[cgarr]

I know on a carbureted engine its important or helps to taper the ports/intake towards the head to keep the speed of the fuel/air mix suspended and to help charge the cylinder when the valve opens but on a turbo or injected motor I don’t know if it would really matter that much since you can really increase the charge by increasing the boost? I don’t know I am just thinking out loud..

[cstreit]

Originally posted by cgarr
I don’t know I am just thinking out loud..

No wonder it was so quiet.

I'm going to speculate with Craig... I but it seems that the factory did the opposite... Could this have something to do with the CIS of the time though?

[Eagledriver]

Yes the smaller ports should be better for you because your engine is turbocharged. This would be closer to the turbo heads (32mm I believe). I hope you are putting lower compression pistons in.

-Andy

[mb911]

looking at some nice JE 8.0-1 for turbo application pistons from henry.. As I read more I see the spectrum OF CR for turbo cars was as low as 6.5-1 and as high as 10-1 so What had was not out of control but did not like to over boost