911 sc 3.0 performance upgrades
 

Hey guys

Looking at rebuilding my engine on my 3.0 sc engine just wanted to start a discussion on advice of what people have done to there stock engines with out going to crazy.

SSI system?

Change out the Cams or rebuild the stock?

Upgrade CDI to MSD ?

Install carburettor system?

My goal is to essentially just upgrade and breath life back into the 3.0 engine.

I understand the 3.0 engine is a beast on its own but I guess what I want to do is essentially upgrade any of the old archaeic technology.

Are you rebuilding the engine (or having it rebuilt), or do you want to add performance modifications? Obviously making sure you have a healthy engine is a prerequisite to waking it up a little more with performance parts. That said, if you have a healthy engine, SSIs, a 964 cam grind and an EFI system with electronic ignition would meet your criterion in your last sentence.

There are no real issues with the engine at all atm besides needing a good service and valve check going to investigate optioions with a few porsche specialists on tuesday

I was amazed when I swapped from the stock heat exchangers with the cross over pipe to SSI's or even just heat exchangers from an early car (pre-cat) that gave me the ability to run a 2-in muffler. I did run an M&K muffler, which sounded faster and removed a lot of weight from the very rear of the car, but these simple things gave me a 3.0 that felt like a whole different motor, really engaging at high RPM's.

exciting, will definatley lean towards making this mod first

I redid my SC with 9.8:1 compression Euro pistons, SSIs, 993 Super Sport cams, SSIs, MK muffler and twin plug ignition...The car absolutely rips and has lost all of its previous laziness. ITBs and EFI would have made it even sharper.

If I didn't already have a 930 though, I might go turbo: stock pistons with 8.5:1 compression is perfect as are the cams, stock exhaust bolts right up to the euro turbo J pipe. Then all you need is a nice little turbo, and Leask WUR or TBitz EFI kit. Instant 350HP.

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Instead of changing to a MSD you might want to switch to the Classic Retrofit CDI. If the Classic Retrofit CDI was available when I had my CDI rebuilt, I would have gone that route.

Classic Retrofit CDI

Classic Retrofit CDI+: Dyno Results

Set you cam timing at one extreme or the other. You want low end, set it there. High end, the other.

964 cam is cool. I have a set on the shelf waiting. Would set timing on the high end to maximizing the cam's better breathing characteristics. Pretty sure you don't kiss low end grunt goodbye with that cam (both cams are nice but pretty wimpy) but would rather see you stay with the SC cam if you are a hole shot lover.

You should have five thousandths of an inch fly-cut off you heads when restored. That is 0.2 points of compression. You have a 930-10? That now gives you 10:1 compression. You are getting close to having to study to do the right thing regarding engine timing. Don't be a pig tweaking timing.

If you don't do a thing, just get the engine running correctly after rebuild.

I assume you have a ROW version which should have large part heads and higher flow injection like '78/'79 U.S. versions. They were pretty quick stock. There are some good tips here and you could search for more.

The first modification I made to my '82 were SSI's and an M&K 2/1, nice power gains here and fairly simple - worth the price just for the sound. With 964 or similar cams a ROW 3.0 SC should perform very well.

I purchased many parts for my anticipated build (Max Moritz P&C's, 964 cams, early 3.0 high flow heads and CIS, etc.) in advance to help offset the financial pain of the rebuild, but you may have a bigger budget than I have.

Also consider a 7:31 R&P or gear set swap for the 915 for more mechanical advantage, and you may want to consider a LSD to help aid traction. I replaced my 2nd thru 5th gear sets and added a LSD/TBD and Wevo internal gate shift to a spare 915 I have, but it was very expensive. If you are going to rebuild the engine anyway I would suggest the engine mods first and maybe later (when the 915 needs work) look at modifying the transmission.

Good Luck, please let us know what mods you perform and comment on the newfound performance.

The is all amazing info thanks guys, I definitely have got the bug to upgrade now.

You could also drop some weight off the car and rebuild the suspension for good effect.

-Steve

I've been dropping weight off my SC through the usual methods: no crash shocks, fiberglass bumpers, no heat exchangers, no cat. Installed stainless headers and M&K 2 in 2 out. Then did Torsion bar upgrade (22/28) elephant poly bronze, Carrera sways, Bilstein shocks appropriate to TBs. WOW. Even though the engine has not been touched (other than exhaust) it is a very very different car. The weight change alone was dramatic, but combined with the new suspension the car is fantastic. Plan to continue the weight loss with lighter seats, RS carpet and door panels. Already at 2450 lbs. wet with half tank, hope to break 2400. Losing weight in the car (and driver) seems to be a very cost effective way to improve performance.

Stay away from the 7:31...They won't last. Money is better spent on 2-5 gears. LSD is a great call - I added one to my 915 along with a Wevo gateshift, but opted against swapping out gears for cost reasons. You have stop somewhere, and I'm making enough power it doesn't matter.

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Have this engine in my 73.5:

Upgrades include 1) Max Moritz 3.2 liter pistons and cylinders, 2) 964 cams, 3) Raceware hardware, balanced rods, Carrera oil pump. New parts included: intake valve sleeves, rod bearings and rods balanced, and rocker arms.

Retained the CIS, has the early car exhaust and low gears. Luv it...

Dam you large port CISers. ;) yes, I am envious.

Large port...OVER RATED.

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Rick, if you want large port, I have full large port CIS.

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Not if your engine is a 930/10 with 964 cams and SSIs

Large ports are fine, but unless you're running non-common plenum cams, (e.g., S cams and carbs), it's not needed. Speaking from experience, I'm running 9.8:1 Euro pistons and 993 Super Sport cams on small ports.

I even bought a large port setup and decided against using it after a long conversation with a builder who has done multiple motors builds of similar spec on large and small port. I can say without a doubt that the importance of big ports is indeed overrated.

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The only time you NEED the large-port heads is when you using aggressive cams such as early "S" cams, GE60's or more.

For street use, port velocity is more critical than simply high flow volumes.