Base vs S - weight

[Paul]

The 2.7 is a nice motor, it revs freely, sounds great, and has sufficient power. But then I have almost as much fun in my 924S as in any of my other Porsches.

[Boxx]

Alright, I see.

An "S" is definitely a different block than the base,
though it looks the same from the outside.

There's just not enough metal to bore out a 2.5/2.7 into an S 3.2.
The cylinder walls would be way too thin to change the bore by 7.5mm.

So Porsche didn't just rebore the Base motor into a (relatively) big-block.
Nor did they expand the motor to accomodate increased cylinder volumes.
They kept the rest of the motor identical and just re-cast the S cylinders larger
(and maybe a mm or 2 thicker) and jammed them into the same Base block.

So there's alot less room inside the block for the water jacket.
It doesn't seem marginal either. Looks like half as much water-jacket
especially on the ends of the outer cylinders. I'm guessing heat problems.


At least that's how I read the block internals pics from Paul and BYprodriver.
Thanks guys. And thanks to boxxster who figured it out and explained it to me.