3.2SS or 3.4 for my new engine? Opinions please.

[butzi73]

Fellas,

The time has come for me to put a new engine in my car and I need some opinions. The 2.7 has a loose crank shaft. It actually ran great when I pulled it to put in a clutch, but discovered there is slight vertical play in the crank. I've decided that I don't want to dump all the rebuild money into the same motor. Even though I loved that motor, I figure I should go for more power now (feel free to try to talk me out of that). I haven't torn it down yet. The rest of the motor is still pretty fresh. I likely will sell it, I’m just not sure if I want to part it out or sell it complete yet.

So, I’ve come down to deciding on two engine choices: 3.2 Short-Stroke, or a 3.4. I’ve driven a few different engines in early 911s (2.2, 2.7, 3.0, 3.3, 3.6), but not these two yet.

My big question is what will the difference in character be between these two motors? I know that displacement is only one factor in ‘character’. Port, cam, exhaust, intake, etc. all have an effect. But, I still have to make a decision on which base engine to get so I can get started: 3.0 for the 3.2SS, or a 3.2 for the 3.4. So, all things being equal what will the difference between these two motors be?

When I drove the 3.6 I was amazed at the power, but it’s not really the character I’m looking for. Too much power down low. Too modern feeling (probably from the injection). I’ve learned that, although I love torque as much as the next guy, I still need there to be a higher end power peek for the excitement factor. This is what originally attracted me to the 3.2SS. Good displacement, but more free-revving then the stock 3.2. But, I also know I could just as easily go for a 3.4 and have even more power. I know that the power can be put anywhere on either of these engines with the right port and cam so why not just go with the 3.4 right? But I’ve heard opinions that the 3.2SS is the sweet spot for powerful, but still revy engines.

The stroke difference is 70.4mm vs 74.4mm. Will I feel that? With the extra rotational inertia needed with the 3.4 will it be noticeably slower to rev?

(couldn't decided on if I should post this in technical or general)

[Jim Breazeale]

Hi Cary

I'll bring my ratrod with it's tired short stroke 3.2 next Sat for our Rgruppe/Early 911s Registry coffee and donutfest.
We seem to be one of the only groups that meet year around.
The car is yours for a road test.

Regards

Jim

[butzi73]

Awesome Jim. Thank you! See you there.

Cary

[a911s]

The stroke difference is 70.4mm vs 74.4mm. Will I feel that? With the extra rotational inertia needed with the 3.4 will it be noticeably slower to rev?

Yes, provided both are steel con rods. The ideal motor for your needs is twin-plug moderately high compression, somewhere between 2.9 and 3.2L - depending on LS/SS, carbs/MFI.

I've driven pretty much everything from 2.0 R to 3.8 Motec slide valve... If it were me, I would go 3.2L SS twin plug MFI.

[BURN-BROS]

I'm partial to the 3.2SS. It retains the classic feel of the early engines but with the volume turned up a bit...

This one was built to look "correct" in a 72/73.

[pu911rsr]

I've owned quite a few different race/hot rod motor configurations- my last one was a twin plug 3.5. If I were to do another I'd try a 3.2 SS just for the novelty. You can rev 74.4 pretty high as long as you are willing to pay $$ to prep case for lots of oiling mods. My 3.5 revved plenty fast but torque curve was very flat, more E like than S like, monster torque off idle.

Phil

[Chuck Miller]

Cary,

I've driven most 'middle and light heavy-weight' combos and the ones that stick out are 2.7 High compression, 3.0 MFI, and SS 3.2....

I do like the SS 3.2s...

I think you'll like Jim's 'ole parts getter'.....

[butzi73]

Guys,
Thanks you so much for the excellent input! This is exactly what I needed/wanted to hear. I feel good about this decision now. 3.2SS sound like what I want. I'm going for it.

Thanks!
Cary