2.5 liter engine build - am I on the right track?

Willem Fick · 05-23-2014, 02:17 AM

Hi folks,

I have a matching numbers '70T that I would like to add a little "fun" to. Though probably not too valuable in the grander scheme of things I want to leave the car as unmolested as possible so that I can revert to original at some point down the line. I therefore do not want to do any mods to the engine, but rather put that into long term storage and get something nicer to substitute for a while. In this light I also want to keep the 911 transaxle, which limits me to the amount of power the engine puts out (180hp?)

I have looked into the options of a 2.7 and even a US spec 3.0SC, but deep down I really want a 2.5 "stroker".

So;

I happen to have enough good parts lying around to build an engine around the following:

2.7l Alusil P&C

2.2l S crankshaft

2.7l Case complete

2.7l Heads

I have heard that it is possible to put these together as a 2.5l stroker, but see that this is mostly done with Nikasil cylinders and special LN high compression pistons.

So a couple of questions:

Can what I want to do be done with what I have?
If it does work, what effect will the lower compression ratio (I would guess around 8.x:1) have?
What sort of power output range can I expect?

Thanks,

Willem

tom1394racing · 07:48 AM

You will have to have your case spigots bored to accept the 90 mm cylinders.

For a street motor with good low end torque, you might consider a 2.45 liter with the 70.4 mm crank, 86 mm P&C's with 9.5 CR and a modified S cam.

Check out this thread

Which Cams?

burtm5 · 05-23-2014, 11:18 AM

What exactly do you have? If you have CIS 90 mm pistons they won't allow E cam or bigger to fit. If you have 74 small heads at 32 mm intake you don't have much. The 2.2 S crank (it is 66 mm right) is a very valuable piece. If its a 2.7 or 70.4 mm crank I would just build out a 2.7. Alusils are not loved for re-ringing. Have you got the carbs, intake manifolds etc.I had a ss 2.5 for 30 years and really liked it even though as you note only had 8.0 or less CR. best Henry