930 3.0 SC to 3.2, what should i do?

[Porschekid962]

This summer my 78 3.0 sc is due for a rebuild. I have gone between the idea of upping the compression and staying 3.0 or just moving up to a 3.2 where i have the option to run the 3.2 dme. can i bolt the 3.2 p's and c's onto the 930 case with the original crank or are there head spacing problems? i plan the port and polish the heads, possibly twin plug and also move up to an S cam. are there any threads on something similar to this??

newbie to engine building.

[emcon5]

This summer my 78 3.0 sc is due for a rebuild.

Why? Not doubting you, just curious.

I have gone between the idea of upping the compression and staying 3.0 or just moving up to a 3.2 where i have the option to run the 3.2 dme.

Are you talking about swapping your CIS engine with an 84-89 Motronic 3.2, or installing 98mm P&Cs to get a short stroke 3.2 and run the factory 84-89 fuel injection?

can i bolt the 3.2 p's and c's onto the 930 case with the original crank or are there head spacing problems?

Depends on what you mean by "3.2 p's and c's" See Wayne's thread here: Quick FAQ 3.0/3.2 upgrades to 3.2/3.4

i plan the port and polish the heads,

78 has the large port heads. Whether port/polish will do anything for you is a matter of debate, which seems to depend on what cam you are planning on using.

possibly twin plug

There have been a few discussions of twin plugging, and the many ways of making this happen. Start here:

twin plugging question
Opinions on twin plugging with race gas

also move up to an S cam. are there any threads on something similar to this??

The early S cam will not work with CIS or stock Motronic.

What is your goal, hot street car, full track car, daily driver?

Will this car have to pass CA smog?

Tom

[Porschekid962]

hot street car and track car, no worries about smog since the engine does business in my 74 911s, twin plus is now out after talking to tyson at tre, he also said i cannot bolt the 3.2 pistons onto the 930 case since one i think he said the 3.2 has an o ring seal and the 930 case doesnt accept it. i can always burn a new chip for the dme to accomodate the new s cam. if i change the cam from the 20/21 to the S then the CIS is up for sale. thanks for the links.

[Porschekid962]

if i used it solely as a daily driver than i would wait longer for the rebuild but seeing as the car and engine will be on the track as often as possible i think a rebuild now would be better than rebuilding after something has gone wrong at the track. plus a little more hp is always a nice thing!

[Tyson Schmidt]

Originally posted by Porschekid962
hot street car and track car, no worries about smog since the engine does business in my 74 911s, twin plus is now out after talking to tyson at tre, he also said i cannot bolt the 3.2 pistons onto the 930 case since one i think he said the 3.2 has an o ring seal and the 930 case doesnt accept it. i can always burn a new chip for the dme to accomodate the new s cam. if i change the cam from the 20/21 to the S then the CIS is up for sale. thanks for the links.

Actually, I said that the 3.0 uses a head gasket and the 3.2 doesn't. You can interchange the barrels though. But why would you? They are the same bore.

As far as POC classification goes, it would make the most sense to limit your mods to cams and compression. To complement that, and to take full advantage of the cams, you should install ARP rod bolts, Ti retainers, and Aasco valve springs, so you can raise the rev limit. JE pistons would be wise, since you could run any compression ratio, and have valve clearance in case you go with wild cams in the future. I recommend 10/1 C/R pistons. 20/21 cams for a nice compromise, or 993SS cams if you don't mind a bit of a lumpy idle.

Now if you get crazy and want to run carbs or Motec, then some GE60 cams with the above mods plus some port work, and some stepped headers. But then you're running with the big dogs.