2.7 Engine - aluminum vs magnesium case? What would you get?
 

I am going to get a new 2.7 engine for my 1972T. I am looking at two different engines, one that is an aluminum case (from the mid '60's) and a standard 2.7 mag case.

From purely the case perspective (all things being equal), and both built by knowledgeable rebuilders (case savers, ect.)

Which case would you choose, and why?


Thanks.

Go with the aluminum case if you can. Magnesium isn't as strong.

Magnesium is a LOT lighter and the 7R big spigot version is very strong. If the case issues are addressed, it's a better "Fit" for your '72T which originally came with a magnesium case (a 4R or 5R). Only the very knowledgable would be able to tell that it's not original and they'd have to get under the car to do it. . . vs. AL which is immediately obvious.

Depends, IMO, how fast you spin the motor. Anything 8K and over is pretty destructive to magnesiuam cases, especially on 70.4mm cranks. My guess is you are looking for an RS spec motor, so I'd go mag, as long as it is a 7R. They are light and look correct. If doing something exotic, like a 2.6SS, I'd absolutely go Ally.

Why? Aren't 66mm cranks stable?

It isn't crank related; sorry to be unclear. Aluminum cases are good if you want large spigot bored (92mm P/Cs), regardless of crank.

Well, the 2.6SS has the same spigot as the 2.7RS ... :D

Woops; had some numbers mixed up. Both use a 97mm bore, don't they? Tha's why the 2.8 skirts tend to fail; too thin. Still, I wouldn't build a high revving motor with 97mm spigots on a mag case.

Hello there.

I'd ask the temeprature you expect to see.

Mag is strong, and excellent below 180 degrees, when it suddenly softens.

Cool ambients, cool oil, cool everything, and mag is great.

Kind regards
David

It's the 2.9 skirts that tend to fail, not 2.8.