930 3.0L Pistons into 3.2L Carrera engine...

[WydRyd]

Hi gang,

I'm curious, will a new set of 930 95mm 3.0L Pistons slip right into my 95mm Carrera Cylinders?

Obviously these two engines have different strokes (70.4 vs 74.4), so what would be the C/R if I used these pistons in my engine?

I'm weighing up whether I should use a used set of 930 3.3L P&C's (excellent condition) in my rebuild, or whether I should just buy a new set of 930 3.0L pistons & rings and slip those into the existing liners?

Will new pistons & rings in used cylinders pose any reliability issues?

Advice/recommendations/flamings anyone?

[Wayne 962]

Hmm, 930 95mm pistons, that would be the 3.0L pistons from 1976-77. They would not work with a 3.2, as the piston pin diameter and offset are all wrong.

Wait a sec, well, to *specifically* answer exactly what you asked, yes, the pistons will slip right into the cylinders. Even if they fit your crankshaft (which they don't) these are turbo pistons, flat-topped, and very low compression.

I'm weighing up whether I should use a used set of 930 3.3L P&C's (excellent condition) in my rebuild, or whether I should just buy a new set of 930 3.0L pistons & rings and slip those into the existing liners?

I give up. I've read your post now about five times, and I can't figure out what you're trying to do. Neither of those will work in your normally aspirated engine.

Oh wait, you have an aftermarket Turbo kit (just read the signature).

Okay need more info then on your entire engine.

-Wayne

[john walker's workshop]

different pin heights, won't work.

[WydRyd]

LOL!

OK, OK, what about some aftermarket 95mm pistons spec'd at say, 7.5:1 C/R.

But then again, I keep hearing such negative things about JE Pistons that I just don't know what/who to believe

[A Quiet Boom]

WydRyd,

I called JE about custom 7.5:1 for my SC the other day and they will make them at a reasonable price (about $150.00 ea) now I just wish I had Nickasil jugs to put them in. I haven't searched the board yet for JE's so I haven't heard anything bad about them but I've gotten great reviews from V8 and 4cyl guys who run them. In fact the tech guy at JE was out racing his 911 when I called so I talked to another guy woh gave me the ballpark price.

[Lukesportsman]

A Quiet Boom:

The "news" I hear around the P car camps is that they can separate at high rpms. I'm not sure what is so special about a Porsche at high rpms! For the most part these are short stroke engines compared to where JE has made their reputation. Drag cars run 8-10k rpm granted for much shorter life cycles, but have longer strokes and much higher piston speed. Piston speed is much harder on a piston than HP per cylinder. How many rods are destroyed by hp, or torque more accurately, versus too many rpm?

Builder error still kills more engines than quality parts failing in my opinion. These issues concerning JE are NOT MINE, yet what is floating around. Going stronger against this issue, I have all intensions to purchase JE pistons in the future (for both P cars and other).

Bad luck just happens, no matter the preparation. Due you think NASCAR or F1 teams use inferior products at their budget? Haven't you seen both blow up in the first lap? One part failure doesn't da*n a company.

Luke

[A Quiet Boom]

Luke, actually the stroke length on 3.0+ 911 engines is close to most small block V8's. A small block Ford 302 for example has a stroke of 3.0" or 76.2mm. So I doubt that's the issue even though most drag V8's do in fact have much longer strokes. I'd be willing to bet rod angularity caused by short rods or higher piston temps in an aircooled engine play a larger role in most failures than piston speed.. You're right though, most problems come down to builder error. High rod angularity and high rpm don't go well together because their is too much side loading on the pistons.