911 sc 3.0 performance upgrades

[zelrik911]

Originally Posted by hellblau82

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

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.

[hellblau82]

Originally Posted by zelrik911

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.

[zelrik911]

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

[Joe Bob]

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.

[al lkosmal]

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

regards,
al

[wreckah]

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.

[DoninDEN]

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

[wreckah]

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

[angelny911]

Chime

[RSBob]

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

[al lkosmal]

yes

[mikedsilva]

Did you end up going through with the mods?

[Superman]

Originally Posted by David 23

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.

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

[Superman]

Originally Posted by Steve@Rennsport

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.

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.

[Superman]

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

[chrisbalich]

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.

[G450X]

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?

[Josh D]

Originally Posted by G450X

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.

[fred cook]

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 !

[WP0ZZZ]

Originally Posted by fred cook

Compression wound up being more like 10.8:1 due to machining having been done on the heads.

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