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

[messix]

rod length brings up alot of issues, longer rod to strock ratio will decrease the side forces that scuff the piston to the cylinder, this does reduce friction. it also incresses the tdc dwell time , this can cause problems of to much combustion pressure make for higher head temps and also detonation prone. Jake chime in her any time.
shorter rod to piston ratio is the anti to these, but also will have a stronger induction pulse due to the faster piston speed and accelerations. also same goes for the exhust. this can make up for a non-ideal intake port [size of port or valve or both] how ever the exhust could be hurt by not having time to flow all the gasses out.

just a big balancing act on a tight rope

that why not everone builds race engines and the good ones have engineering degrees