1983 SC based race car - need more power!

[jwasbury]

The car is awesome, best of everything, but the engine leaves a lot on the table. 3.0 liter, standard compression ratio, standard cams, etc. Supposedly built with Pauter rods, but I haven't had it apart to verify. Induction is very trick, Jenvey ITBs, 964 plenum, Motec EFI. Exhaust is custom. The ITBs and Motec were installed and tuned by Rothsport. Runs great, but I'd like more power (who wouldn't).

Not building to any specific class, but the car was tagged NASA GTS4. According to my discussions with the seller and the good folks at Rothsport this engine made ~240 crank hp, which if my weight estimate is accurate says that in current trim this car would be at the blunt end of GTS4 class.

My thoughts are bump the compression ratio, put in some better cams, maybe displacement increase (go 98mm, 3.2). Seems a waste to toss the cylinders assuming they are still good, so the minimalist route would be simply pistons, cams, retune ECU. Maybe get a better exhaust (Rothsport guys mentioned they thought the exhaust was holding it back as is).

How high is safe to go without twin plug. Looking at Bruce Anderson's book, I see the Euro 3.2 Carrera was 10.3/1. And what cams do people recommend? With ITBs I can do pretty much anything, right?

Pics because...

[JohnJL]

Supercharge it.

[saxen]

you may consider selling your current engine and going with a stock 3.6- you will gain another 30-50 hp and be reliable.

just a thought

[JV911SYDNEY]

Seems strange that it would have been built with Pauter rods but with standard everything else.

What do the (ever helpful) chaps at Rothsport suggest?

Of course if you went with new P&Cs you could both up the displacement and compression.

964 cams are common but given the Motec you could get something with more lift and duration without sacrificing drivability. Once you've settled on displacement & compression I'd speak to Elgin and get something custom with a custom grind.

I can’t comment on twin plugging as it’s not common in Aus (better fuel). The Motec should allow for a bit more comp though.

All this depends on your budget and what can be reused, but as I see it “stage 1” would be cams, springs, retainers and a retune. Stage 2 would be pistons for more comp, Stage 3 would be more comp and displacement. Stage 4 would be a balls out rebuild.

Whatever you decide, keep us posted!

Originally Posted by saxen

you may consider selling your current engine and going with a stock 3.6- you will gain another 30-50 hp and be reliable.

Or better still, putting the ITBs on the 3.6. However there is no guarantee that a used 3.6 is going to be reliable.

[saxen]

Originally Posted by JV911SYDNEY

Or better still, putting the ITBs on the 3.6. However there is no guarantee that a used 3.6 is going to be reliable.

you and I need to be friends

[jwasbury]

The engine wasn't updated with cams and pistons because the PO was building to the Spec 911 class.

Supercharger? hmmn. Forced induction has crossed my mind (my other car is a 930), but I am enjoying the NA experience.

My first thought was to purchase a 3.6 long lock, transfer the ITBs. Would not do stock 3.6 as there's no way I'm giving up ITB throttle response. A 3.6 core isn't cheap, and I would end up rebuilding the whole thing from the crank out. Depending on what needs doing, by my research if I take this route I need to be prepared to drop 25k (not factoring sale of current long block, I'd keep it). While I don't have a specific budget number in mind, I'd rather not put that much $ into this car.

I'm going to call rothsport and see what they recommend re: pistons and cams/exhaust. Still interested in opinions from the forum too.

[JJ 911SC]

Originally Posted by jwasbury

... I'm going to call rothsport and see what they recommend re: pistons and cams/exhaust. Still interested in opinions from the forum too.

Keep us posted.

[Steve@Rennsport]

Originally Posted by jwasbury

I'm going to call rothsport and see what they recommend re: pistons and cams/exhaust.

THAT is the best thing you can do.

Jeff is very very good at this and once you give him your budget & objectives, he will tailor a package for you.

[Sboxin]

+1 Steve

We have a friend that is very fast with a short stroke 3.2L w/ 3.o case and PMOs.
But his secret is the wide body suspension and rear coil overs . . . and low weight '72 body.

Maybe spend some on engine and some on wide body . . .

Regards,

[jwasbury]

Originally Posted by Sboxin

+1 Steve

We have a friend that is very fast with a short stroke 3.2L w/ 3.o case and PMOs.
But his secret is the wide body suspension and rear coil overs . . . and low weight '72 body.

Maybe spend some on engine and some on wide body . . .

Regards,

This car is pretty tricked out already on the chassis front, I don't think I have many excuses there

Not wide body, but some of the biggest tires you can fit under stock flares (Hoosier R6 275 in the rear 245 up front, IIRC), full coil overs (Moton 3 way adjustables), Smart Racing sway bars. Fully gutted, lexan windows all around, so only thing left on weight reduction side I can see is to replace steel with FRP parts. I could easily drop 67 lbs with hood and front fenders in FRP, after that it gets hard. That's on the to-do list at some point also.

My home track is pretty big (3.8 mile circuit) with some long straights...I'm getting crushed by the bigger hp cars on those straights.

[lindy 911]

Twin plug 3.0 with 10.5:1 JEs, PMO 50, GE 80, European 1 3/4" headers = 300 chp. Excellent race power.

[Matt Monson]

Yep, call Jeff. Cams, pistons and some headwork and the rest of your package puts you north of 300. Jeff has an engine dyno. He'll give you an actual crank number before the engine ever leaves his place. And it will be tuned properly. No further fiddling.

[jwasbury]

I called Jeff. While he's happy to give his time and discuss in generalities on the phone, he's not interested in giving specific advice and selling me parts so that I can do the install. I'd have to ship my engine across the country, which is not something I'm prepared to do. Fair enough. S'pose I'm spoiled by guys like Chris Carrol of Turbokraft who was open and honest, provided excellent counsel to me as a DIY engine builder, and I bought parts from him as a way to "pay" him for his time. This isn't my first tango: Jacob's rebuild thread

At any rate, my next trick is to call Dawes in PA. They are near to me and I figured I would call upon them for Dyno/Motec tuning assistance after I do the R&R of go fast bits.

Lindy 911, appreciate those details - that's the kind of feedback I'm looking for here.

As an aside, there is a tasty looking 3.8 RSR build for sale in the parts classifieds. One avenue would be to negotiate a purchase of that engine, then sell what I've got as is and complete. My engine is built to SPEC911 class so would be plug n play for someone who wanted to race that series. The 3.8 RSR is more power than I really envisioned, and I would need to spend some $ on my 915 to make sure it survived.

[304065]

Peter's one of the best and one of the nicest guys in the business.

[Europeanmotors]

Pretty sure for the 3.2 a lot of people were dumping 964 cams in it all day long, not sure with the sc's though because the pistons are different (along with a few other things)

[Matt Monson]

Take a look at what a bunch of the POC guys supported by Aase run. There's a JE piston they all seem to run with similar cams. I'm sure if you put a similar thread in the racing forum you'd get some additional traffic.

[3literpwr]

Keep engine... Change racing format!!!!

https://www.youtube.com/watch?v=rbLD_xkLefA

[JV911SYDNEY]

There are a couple of threads on this topic on rennlist at the moment. The consensus is:

3.2 (98mm) JE pistons
964 cams
recurved dizzy if running CIS (or retune in your case)
SSI headers
twin-plug if comp more than 9.8 in the US


Which cams would work best on a 3,2 SC with 46 PMOs ? - Rennlist Discussion Forums
Upgrading 3.0 into 3.2 - Rennlist Discussion Forums

[Dan J]

Peter, Trevor and Kevin Dawe will be able to do alot with what you're starting with
You won't find a better group anywhere

[Matt Monson]

Peter, Trevor and Kevin Dawe will be able to do alot with what you're starting with<

You won't find a better group anywhere

Words from a man with both humility and skill beyond his years...