2.5 shor stroke engine, my plans Options

[michel richard]

So here's what I'm doing for the engine as part of my "GT style" conversion. First and foremost, I figure that an engine in a GT style car has to be rev-happy.

So, here's what I'm putting together, with the help of my trusty wrench, Ron Green of Campbell Gararge in Montreal:

Short stoke 2.5 Porsche engine:

1) Used 7R engine case, align bored, Timeserted, shuffle pinned
2) 90 mm JE pistons, 10.5 compression ratio
3) 90 mm replated Nickasil cylinders, sourced from EBS
4) Standard piston ring set
5) 66 mm counterweighted crankshaft
6) GE 80 camshafts
7) EBS racing valve springs
8) EBS valve spring retainer set for above
9) 2.0 connecting rods
10) ARP rod bolts and nuts for above
11) twin plugged heads
12) Electromotive HPV twin ignition
13) Turbo lower valve covers
14) front mounted ol cooler with "GT Style" installation
15) new bearings and gaskets all around
16) miscelaneous engine parts, stock.

I still need to figure out what to do with the port sizes in the head. The target is to have a 8,000 rpm redline, and 250 hp, although the redline is more important than the hp to me.

So that's the plan. I pulled the trigger on the hard parts above today. ( I already have the crank and the miscelaneous parts).

Induction is going to be 40 mm PMO carbs, jetting to be determined.

I'll post to this thread as progress is mad on the engine.

Michel Richard

[michel richard]

Gentlemen,

The reason for going to 2.0 rods is that ARP does not make rod bolts specifically for the 2.2 rod. I'm not going to the 2.0 rod to save money: I already have 2.2 rods in my current engine.

I spoke to Henry Schmidt. He has a solution that uses 2.2 rods, rod bolts that ARP designed as steel replacement parts for 935 Titanium bolts, along with 928 rod nuts. The problem with that solution is that it's fairly difficult for me to source all those parts at a reasonnable price. Henry agrees that the 2.0 rod solution is a workable one.

On the other hand, the people at EBS say that plenty of 2.5 short stroke engines have been built using 2.0 rods and ARP bolts and that they work fine.

So, for a full race engine, I'm sure that using aftermarket rods is a better solution, but I think that for a hot street / some track engine, the 2.0 rod /ARP bolt solution will work. I'll go with those and let you all know how it works out.