I want 225hp, how to get there?
 

Hey everyone,

I'm thinking 225hp (crank) would be a nice amount for a driver that I can have some fun in. Not a track car but may hit Road Atlanta once in a while seeing as I live about 8 miles from the track.

The car,
1979 SC, California car (if that matters) 172hp. Completely stock 3.0 with the exception of a M&K Cat Bypass pipe, air pump removed and CIS. I believe it has 8.5-1 compression.

The car has 78k and last year the PPI showed 2-3% loss across the board and the car currently runs great but, I have no basis to compare.

How would one go about reaching the 225hp goal in this situation?

I'm already planning on going with CDI+ and SSI (not sure on muffler) exhaust but would like to stick with the CIS for now as I've read that CIS can handle 250-275hp, not sure if that's accurate.

Would cams and higher compression pistons do the trick? Can I get just higher compression pistons or would I need to get the cylinders worked over?

I would be great if I can accomplish this without splitting the cases.

I do see PMO carbs or ITB fuel injection in the future but would like to do that later.

Thanks!

I’m new to the forum but from the info i’ve read the Euro Spec 3.0 engine will get you pretty close to 225hp. I will certainly be following the thread.

Yep, that's what I was thinking, I seem to remember reading the euro spec motors were 9.8 to 1 with around 207hp, I could be wrong on that, and I figured with pistons and cams along with the CDI+ and SSIs just might get me there.

Early SC CIS is pretty easy to tune for HP. One of these days I need to dyno my 1978 targa (98mm P&Cs, 9.5:1, 964 grind cams, SSIs) but the butt dyno says 230hp. If I built it again today I'd definitely use William Knight's M1 cam.

98mm Mahle 9.8p/c,, ssi + good muffler and cams ought to do it

if retaining CIS get the cis version of the pistons

98mm is for a 3.2 conversion, right?

correct

for most street use a btter torque curve is more important than top end hp

When I rebuilt my 3.0 (small port) a few years ago I did the SSI's and the 964 Cams. (But I'm intrigued by the M1 cam....I'll be listening if the discussion goes in that direction. )
I used the stock cylinders (plated with Nikasil) and bumped up compression with Max Moritz style pistons from J+E. To compare, my brother's mostly stock '79 SC (haven't touched the engine, just did SSI's) was peppier than mine even with all those mods (big ports make a difference) That said, I put a Kennedy lightweight pressure plate on a couple months ago and man that made a huge difference in the feel. Much more revvy and exciting to drive. I would not want a 911 with a stock pp. The lightweight one didn't affect street driving at all (spinning down too fast and being a pain to shift I mean) and did nothing but make the car more fun to drive.

Would this be possible maintaining the stock cylinders and just higher compression pistons?

Probably

here are some stock engines
930/18 aka SC/RS 3.0, S cams mfi 10.3 cr250hp@7000 188lb-ft@6500

930/02 76 Carrera 3.0, 3.0 basically an SC w/ better tune , 200hp@6000, 188lb-ft@4200

930/10 83 SC(RoW) 9.8cr 204hp@5500 190/lb-ft@4300

'84 Carrera 930/20 10.3 cr 3164cc, 231hp@5900, 209lb-ft@4800

so a 3.0 95mm bore w/ cams, sssi+muffler+ignition tuning 9.8cr ought to be in the low 220 hp area

It's just that there is no replacement for displacement on the street

that's' why so many have gone for a 993 3.6, stock 272hp@6100, 242lb-ft@5000, 11.3cr, knock sensors just in case gas is poor

I recently dynod an 80 SC

98mmJE 9.5:1 comp w new nickies
20/21 web cam
SSI’s
CIS

It only made about 170hp to the wheels. Checked on 2 different dynos very surprising. The car drove like a bat out of hell though much quicker than a stock sc.

That does not sound right.. you may want to look into you cam and ignition timing.

Either the dyno is broken or you had the wrong car on it...

It's not answering your question, but a more reliable and predictable way to get better performance is to change the gearing in 2nd through 4th gears (leave 5th alone for cruising).

SSI's and a muffler will make it sound like it has 250Hp!!!

Interestingly, I started with a '78 Targa, of the exact same spec, 11 years ago...and began down the slippery slope with similar mods you've mentioned.

I ended up going down the hot rod road and hunting for a euro 3.0, which I was grateful to find a freshly rebuilt one on here. That motor currently has Dougherty Cams "964 RS Spec", headers, M&K exhaust, and some other small basics, running strong on stock CIS... making 212whp on a Dynojet.

Your instance of a low mileage car with great leak downs so I'd imagine that a motor swap wouldn't be in the cards.

My opinion would be to build the top end to euro spec, P/Cs, maybe a little head work, and some mild cams would really run amazing.

Last $.02, PMO Carbs are really great when tuned properly. CIS is more solid and robust than carbs, just not as sexy. The ITB Juice isn't worth the squeeze. Before you consider blowing 15-20k on ITBs, do your homework on your ROI.

There's a good discussion of this topic here.

The early SC’s (U.S. spec) I’ve driven and been a passenger in all seem to be very quick. I suspect maybe Porsche was conservative in their power figures for some reason? There is a C&D road test of a ‘78 SC targa that was basically as fast as a later 3.2 Carrera. The later small port “emissions friendly” SC’s seem to have gained a few mpg, but lost some power.

It would be nice if a factory Porsche 911 engineer from that era could provide some insight into the early vs late SC power differences. Could the large ports and higher flow fuel distributor (even with 8:5:1 CR) really make that much difference? I could believe Porsche provided C&D a 3.1 “special,” but all of the early SC’s I’ve been have all seemed to be very quick…

Not an engineer but you're accurate regarding the 78-9 Big Port motors. I know that a local race shop who is very successful in the Air Cooled Cup series, prefers to build their race motors using a base of a "big port" motor

Here's a data set for air cooled 911

http://forums.pelicanparts.com/uploa...1655833203.gif

earlier list I forgot the '74 Carrera 3.0RS
3 liter, S cams MFI 230hp@6200 206lb-ft @5000 9.8 cr

to build a close modern rep. of it
9.8cr Mahles, TBI, Motec, S cams, SSI +muffler

I wouldn't change the gearing as it was pretty appropriate for the rev range and weight of these cars, It wouldn't hurt to have 225/45 or 245/45 x16 or 225/50 or 245/45 x15 tires in back

An older Mustang GT with a 5 speed will do it.