Need details on the 2.5L motor

[cnielsen]

I am trying to decide if I want to build a 2.5L motor for my next car. Was the 911ST equipped with the 2.5? I am trying to figure out if the factory ever made this combination and if so, what the specifics were. From Bruce Anderson's book, it appears like the 911/70 engine may have been that combination but it is hard to tell. I would do custom JE pistons with a 2.2 set of crank and rods with 2.7 Nikasil cylinders. But I am wondering what cams they used for this motor...does anybody have more information on this motor???

Thanks, Chris

[Tim Walsh]

That's nearly exactly what the factory did, except they used 89mm pistons instead of 90 so that they could run in the sub 2.5L class. I think they used the 906 cams if I remember correctly.. wayy too wild for street purposes.

BA also mentions the 2.2 crank + RS pistons as well and it seems to work well except it's low on compression (JE's would fix that). Ask curt how his runs... it's one of my favorite combinations for a small displacement engine.

[Plavan]

I am in the process of building one right now. I probably will be making 2 versions of this 2.5 race motor. The version I am building right now has 85mm J&E pistons with a 2.7 crank/rods. I plan on using the GE-80 cams instead of the 906 cams. (I think my cousin will have some 906 cams for sale here sortly). The other version I will build after this one will be based off on my current 2.7L race motor. I plan on using a counter weighted 66mm crank out of one of my alum case's. Then having some custom 89mm J&E's made up. Then send in my current cylinders in to get them sleeved by 1mm. This second motor should scream.
I should just keep my mind on the first motor until it's done