Those are large bore engines which leave less material at the case spigots for stiffness and expecially important with the early (non 7R) cases.

Its really all about how long you expect the engine to last. :)

So, if Al is the way to go, we might as well go to big displacement like 3.2 otherwise what's the point?

The principal of small displacement is lightweightness but if that isn't possible...

Something like this has been said many times here. It makes a ton of sense but, I dont think there is a single best answer to the 'which engine' question.

In my case, Im going for the lightest possible engine tranny setup I can think of. My plan is a mild 2.5 built on a mag 7R case hooked up to a mag type 911 gearbox. Im sacrificing strength and durability throughout my drivetrain for something really lightweight. Since I may only occasionally see 7000 RPM, I dont think I need an engine that is completely bulletproof in sustained high RPM conditions.

I think people need to maintain perspective & context in cases like this and refrain from making hasty conclusions,....... :) :) :)

Mag-cased engines, if properly configured and constructed, can be VERY durable as long as one is realistic about what it costs to do one correctly and maintains reasonable performance expectations.

For example, I've done a LOT of 2.8's over the past 30+ years and these are not only bloody fast machines, but very reliable with good oil temperature control.

I can tell you that a 2.8 with good close-ratio gears in a light (sub 2400 lb) car, makes a potent combination that rivals a larger engine in a heavier one and is a lot more entertaining to drive.

That said, its all in what we all like and economic realities.

I think those are "Pearls of Wisdom",....:)

An advantage for opting an early alu case over the 3.0 alu case, I've just remembered, is that the head valves are smaller (46/40 as opposed to 49/41.5) thus less prone to valve floating at high revs. Right?

Of the early alu case, is it possible to enlarge the spigots to 97mm? Would there be any seating surface left for the copper base gaskets to sit on?

Hey Shuie,
We use the AL cases for the race cars 2.5Ls and down.
Send your case to Ted at Greman Presion.
Also tell him to convert it to the later cam covers, IF your gona use Carrera tenisors. We use solid ones on the race engines.
Do the oil by pass, Carrera or turbo oil pump, pin mains, boat tail mains and oil squrters. Costs about $1200 or so.

Thanks Don!