1973 911 S...What would you do?

[a911s]

I think the cylinder fin count is different on a 2.7RS conversion compared to a stock 2.4S. Could be wrong though. Also the case needs to be machined. So they may not be exactly alike visually.

I would go with 2.2S pistons for a higher compression 2.4S if you want no mods to the original case. A 5R case is fine for a 2.7RS conversion BTW .

Otherwise, I'd go 2.7RS spec for the torque. I've driven them all (2.4S stock, 2.4S higher compression, 2.5, and 2.7RS - both regular and higher compression). I'd say the last one - like what's in Chuck Miller's 911 now - is the best. But I never drove Eric's old Gamroth built 911..

[RC70SCoupe]

I had Dan and Scott of Scotts Independent put in the 2.2 S pistons in the 2.4 of my S Targa. I had the MFI completely redone. MORE hp than a stock 2.7 RS Spec. GREAT motor!!

[RC70SCoupe]

Link to Dyno Day
217 hp stock muffler and stock air cleaner
http://www.early911sregistry.org/for...n-a-Dyno/page5

[Jens]

Can I change my vote? Is it too late to recommend 2.2 pistons into the original engine?

I see the light now.

[Chuck Miller]

Some thoughts on this……

- A good running stock 2.4S motor is one of best most responsive they ever made…
- It takes a pretty experienced hand to out-drive a 2.4S’s potential.
- My stock 2.4S engine went 164,000 hard miles without ‘much’ complaint.
- After driving other ‘bigger’ engined 911’s you realize 2.4’s (and anything smaller) have a lot of top end bang and not much low end torque.
- Driving a 2.4S w/2.2S pistons is like driving a 2.4S with more top end bang… still not much torque, but like a 2.2S on steroids… lots of fun...
- Going 90mm 2.7 RS piston set gives you a bit more HP, but one HELL of a lot more torque… almost 25% more...
- The more torque of the 2.7 plus still having a relatively high reving engine is wonderful...
- Not all 2.7 RS spec. engines run the same… Tom is right; I’ve driven 2.7 RS spec cars that would be hard pressed to outrun my old 2.4S.
- Running a 9.5 2.7RS engine makes the whole equation even better.
-Even though it’s done all the time, if I could turn back the clock (and had the finical wherewithal at the time) I would have not built my engine on my numbered mag case.
- Any anomaly or problem in the machining, building, running, or longevity of a ‘high performance’ Porsche engine will most likely be blamed on starting with a mag case...
- Lots of ‘good’ head work on the intake side of these engines makes a WORLD of difference in performance.
- After about 55,000 miles of very aggressive driving my 2.7 9.5 RS + spec mag case engine is doing fine……..

It’s a hard call Bobby…

All these options have merit…….

You really need to think of what you want to do with it, what you want to keep of it, and how long you need it to last without complaint…..

All these options, built right, should last a long time giving you GREAT pleasure..........

Hope this helps,
Chuck

[Jens]

Ah yes Chuck, the voice of experience and reason. I've driven pretty much all of them too. My daily hotrod is a lightweight car with a massaged 3.0 that really has made me a slut for torque. This week I built up an R muffler that is virtually free flow and has increased mid range torque even more. I get that 2.4L 5000+ rpm rush of power at 2500 and up with an intoxicating howl. Torque is addictive, but so is that incredible feeling of canyon and mountain carving with a peaky motor at 5000-7000 shifting. Bobby, you have to decide what combination of horse power and torque you value most, as well as how you want to present the car; stock looking or modificated. As Chuck said, you can't go too far wrong no matter what you do as long as you're having fun with it.

[RSTarga]

Some thoughts on this……



- Going 90mm 2.7 RS piston set gives you a bit more HP, but one HELL of a lot more torque… almost 25% more...
- The more torque of the 2.7 plus still having a relatively high reving engine is wonderful...
- Running a 9.5 2.7RS engine makes the whole equation even better.


All these options have merit…….

You really need to think of what you want to do with it, what you want to keep of it, and how long you need it to last without complaint…..

All these options, built right, should last a long time giving you GREAT pleasure..........

Hope this helps,
Chuck

Chuck, What pistons did you use for the 9.5? Are they the Andial Mahle?

[Chuck Miller]

Chuck, What pistons did you use for the 9.5? Are they the Andial Mahle?

Yes.........

David,
That 103 928 02 piston set was the very first part I purchased for my rebuild back in '03.
Did a bunch of homework back then and decided that, that was my starting point.

BTW- They were expensive back then as well.........

[joseph battista]

Hello Guys

Many thanks for all your comments...Now I'm really confused.

Hopefully I won't need to do anything, I'll keep you posted.

The lift is a Rotary and is now NLA, and I believe it is almost 911 specific.

Thanks Again

[Reza]

Joe, just close your eyes and build an engine already. it dont matter which. to keep things simple and binary, let your car decide. its a 70.4mm crank year. therefore 2.7/2.8 is the bulge bracket there. why low compression? that was a compromise.

but dont listen to me man, listen to the car. remember to consider gear ratios too.