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.

Was there any mechanical reason why the car sat unused for so many years?

Get the mechanic to check for broken headstuds and worn valve guides which are the 'normal' issues for your year of 911, If these are good I wouldnt do any more than a super tune-up from an expert.
If you have to do a top end rebuild then that is the time to consider changing cams and ignition. Originality is a big deal now - so any 'upgrades' should not be too obvious.

I appreciate the advice, definitely take it on board

you can have a skim though my blog, basically car was in a front end fire sat for 10 or so years, I restored it.

https://hellblau82.wordpress.com/

to start with I'm leaning towards getting it a good tune and replacing any old rubbers for suspension and maybe putting an SSI system on it.

The auto heat and AC has been taken out I've kept all the pieces if anyone in the future wishes to put it back in.

The CIS and CDI setup I have no issues with its just old technology. It was my dads car who just past away so the emotional attachment to the car for me is high. He passed it onto me as a project to restore because he never could I've learnt so much and my appreciation for cars has really gone through the roof.

Its been 2 years with this and being in the garage working on it has given me a really good hobby that I enjoy. I don't think ill ever get rid of it only use it as a weekend streetcar that turns a few heads.

Checked your Blog, now I understand - great work and a terrific legacy project. Pretty sure my son wont do anything like this after I'm gone! :(

I suggest you look at the the air-injection system & give it the same treatment as the A/C . If you are going for SSIs you will make that stuff redundant anyway. That dam system has hoses going everywhere, even into the CIS distributor. I bet there are tweaks/tuning that can be done to CIS after removal. CIS will be excellent when all the possibilities for leaking vacuum are eliminated.

Something to consider. I had friends with Webers & PMOs on their 911s & it used to drive their wives & neighbors crazy while they let them idle to warm-up for 5 minutes or so. (My neighbors & I hate each other - so I do it on purpose, but you might be nicer than me!). Injection is much more civilised & cheaper than webers.

Keep up the good work

With my 914/6 I went with 964 cams and ITBs, it was a hoot! While everyone likes bigger displacement I felt it was less reliable in the long run.

+1........port velocity rather than high flow for street use.

regards,
al

i went with SSI's, then CDI+ box, then bitzracing EFI. The difference is quite big compared to stock. It's become a different car really.

- CDI+ box gives a little bit better low-end, much smoother, tiny bit more torque, and is programmable
- SSI's give a slightly bigger hit of low-end and some midrange, nothing dramatic though.
- but to make it all work, the fueling needs work...cheapest way to do this properly is the bitzracing kit (MS computer and some fuel rails). This brings the other mods to life, properly enhancing torque and top-end hp. Added to that is a dramatic difference in throttle response. Another added benefit could be longetivity of your engine and better mileage with proper tuning.

What's CDI + box? I have an 81 with SSI, been thinking about 964 cam

it's a modern (programmable) version of the bosch CDI box, made by these guys:
Welcome to Classic Retrofit

Chime

/\. There should be a rule that your post has to be bigger than your signature

yes

Did you end up going through with the mods?

This description fits my car as well, which I recommend highly.

Precisely. If you are using the stock CIS system, then the most aggressive cams will not work for you. With the stock CIS system, the most aggressive cams you can use used to be called 20/21 or 964+ cams. I have them in my '83 3.0 engine. In this configuration, with the narrower intake runners, intake air velocity is greater than with the fatter intake runners of the early SCs. This maximizes the system's ability to 'pack' the cylinders with air before the intake valve closes. Plus, the late-SC pistons are 9.3:1. My car makes 186 lb/ft of torque and (coincidentally) 186 hp at the rear wheels. That's about 205 hp at the flywheel. With those cams, and with the late-SC intake runners, and with SSIs, and the Triad exhaust, this car's power band looks like a table top. Smooth power from 3K rpm to 6500.

Also, your stock ignition system is fine. And more reliable than the aftermarket alternatives. Bosch rules.

i read the whole blog after reading this thread.
i'm super curious what you ended up doing with the engine upgrades.

what a story. inspiring is simply not strong enough of a word.

Early vs Late SC’s
 

I really don’t understand the performance gap from the early U.S. spec SC’s (‘78-‘79) and the later (‘80-‘83) models.

Road tests of early SC’s I have dug up show Carrera 3.2 like performance (mid 5 sec 0-60, QM 95ish) while later SC models were mid to upper 6 second range to 60 and barely break 90 in the QM. I have an ‘82 coupe and my cousin had a ‘78 coupe, and I will confirm that his car was definitely quicker. I understand some early SC’s had fewer options and were a bit lighter, but I don’t feel the slight weight difference could impact their performance that much.

From comments posted here, the higher compression (9:3:1 vs 8:5:1) with the small port heads and more complex emissions system (vs belt driven air pump) should result in a quicker car, but real world road tests prove quite the opposite. I always thought the later SC’s were modified for emissions and fuel economy, not performance, and that the performance returned with the larger displacement Carrera with a more performance oriented induction system.

My ‘82 falls off cam at around 5500 rpm’s which drives me crazy (I have SSI’s with M&K 2/1). Most people comment on the greater torque of the 3.0 (versus the 2.7 or less displacement models), but if I want torque, I’ll drive a pushrod V-8. I hope different cams will raise the redline to a more reasonable level (at least 6500 rpm’s). I want to build my SC with “early” SC performance.

What is the best way to achieve this? What gives the early SC’s their greater performance?

It's really hard to say due to the number of variables. I have limited data points, but when I bought my Euro '80 SC coupe (big port, 188 hp) I drove it back to back with a '84 3.2 Targa (200 hp) from the same dealer. Both were priced within a grand of each other, the SC had about 20K less miles. It still had functioning air pump, a/c and stock exhaust. The SC, to me, clearly felt like the faster car. There was no question, and I bought the SC.

After taking about 150 lbs out of the '80 SC and adding early HE and Bursch muffler, I had the opportunity to drive a friends exceptionally clean '85 3.2 Carrera coupe that had been chipped and had some Wevo shift upgrades. It had its A/C removed. They felt about dead even on acceleration/power. We never did a side by side race, but his car did not feel, when I drove it, any fast than mine.

I know, limited data point, but I agree that the big port 3.0 are better than what they show on paper.

Large port/small port.............
 

About 5 years ago, I rebuilt my 1980 3.0 into a 3.3SS. I used the LN Engineering slip fit 100mm cylinders, 10.1:1 Mahle pistons, 964 cams, an early large port CIS airbox, Carrera heads w/twin plugs and Electromotive XDi ignition. Compression wound up being more like 10.8:1 due to machining having been done on the heads. Used a stock flywheel with an aluminum clutch cover. This "assembly" of parts made an engine that starts and idles well, doesn't overheat when pushed and pulls like a scalded cat right up to the ignition interrupt at 7500 rpms. It is a little peaky until it gets completely warmed up but that usually only takes a mile or two. While I agree that huge ports probably aren't needed on a street engine, the small ports in the 1980 heads and airbox just didn't seem to be the right way to go for a performance engine. The 964 cams added just enough extra oomph to be entertaining without being too rump/rump! If I were to do it all over again, the only thing I would change would be to use the 105mm cylinders and pistons for a 3.7SS !

Interesting. What machining was done on the heads to increase the compression ratio?