The "right" engine for a ST Replica

[Yzerman-45]

Hi there!
I am about to build a ST replica up here in cold Norway, and i have a discussion with the other guys aboaut the "right" engine for such a car. Today i have a 2,7 with 40 IDA Webers. (single ignition system)I know that most of the ST,s where delivered with 2,5,s but wasn.t there also delivered some with 2,7,s?In this article:
http://www.qv500.com/porsche91124p2.php
They say (quote)"Wins at the Daytona 6 and Sebring 12 Hour race's were backed up by others at the Nurburgring 1000km and Targa Florio, a special 2.7-litre ST also securing victory at the Zeltweg 1000km."

So what do you think? Do i have the "right" engine??

[Flieger]

The ST started with a 2,3 big bore version of the 2,2 street motor with Biral cylinders. Then the street motor became 2,4 with the long stroke. The big bore became a 2,5 long stroke. Then they experienced flywheel failures due to vibrations at high speed. They went back to the 66mm stroke crankshaft and used the biggest bore cylinders (only made possible with thin walled Nickasil technology from the 917) to arrive at just a couple cc's less than the long-stroke 2,5. The short stroke 2,5 had the same power and torque (a lot) and revved quick and fast but was reliable.

Some STs used MFI.

The best ST engine would be a 2,5 short stroke (89.5mm bore x 66mm stroke) Magnesium case, Nickasil cylinders, and for the most power and best throttle response, MFI.

[Flieger]

I think the 2,7 at Zeltweg may have been a reference to the development car for next year's Carrera RS 2,7 and RSR 2,8.

[kenikh]

See this thread:

Thoughts on 911/20 ST Type Engine

Building it now, 2.3L ST replica motor for my '69S:

Fully detailed small spigot 7R case (shuffle pins, squirters, light mooning, every oiling mod known to man, etc)
85mm JE pistons @ 9.5:1 CR
'69S heads - ported by Dick Evelrude
Twin plugs (still debating which system to use)
DC44 cams (custom grind; .490 lift at both lobes; 102 deg lobe centers)
Titanium valve retainers
RARE 47mm 4-bearing cam carriers
Nickie cylinders
Rebuilt 2 liter 'S' rods w/ ARP bolts
Cross drilled crank
Fully balanced internals
Fresh 930 oil pump, with full race chamfer on the internals
2.4S MFI pump
52mm>38mm (taper bored) magnesium MFI stacks and match bored and rebuilt TBs
Lightened '69S flywheel

Planned to be good for between 210 and 220 HP (crank) at 7800 RPM.

[Henry Schmidt]

This one will be for sale after dyno run for developement.

Old school with a twist

Supertec has decided to build an "old school format with a modern twist". The base platform is a 2.5 liter, MFI, twin plug engine. The twist is this engine uses GT3 Gen 2 titanium rods and a new peanut shaped combustion chamber.
Why, we wanted to build an 8500 RPM high compression engine that would run on pump gas.
Twin plugging helps with low octane ratings but the new innovation is to replace the standard Porsche hemmi head with a more modern peanut shape chamber. This allows us to run a relatively flat top piston to generate high compression. This one will make a static compression of 10.25 to 1.
We start:
68 aluminum case
shuffle pins
piston squirters
boat tailed (I know, boating makes no measurable difference, but this case was boat tailed when I got it)
oil bypass modification
oil mod for cross drilled crank
Dry film Moly coating on main bearings
Distributor mount modified for late shaft
Mounts welded for MFI pump
Oil pump
Supertec flow modified Carrera pump
Crank 2.2 counter weighted
Cross drilled
Knife edged
Journals ground to 53 mm RSR with .100" fillets for strength (GT3 bearings, dry film moly coating)
GT3 Gen 2 titanium connecting rods (130mm center to center)
911 SC distributor gear (counter clockwise rotating)
Ion plasma surface hardened
Pistons and cylinders: Mahle 8.5:1, 90 mm RS
Supertec head studs
Heads:
2.4 heads with MFI injector ports
Peanut chamber (51cc)
Big valves 47 mm intake and 41 mm exhaust
38 mm Venti Port intake
37mm exhaust port
Heads have been shaved .040" and a .040" dimension shim added. This a shim placed between the head and cam tower to return a shaved head to proper thickness.
Supertec valve springs (90lb seat pressure and 220lb @ .500" lift)
Aasco titanium valve spring retainers

[911pcars]

Glad to hear the engine is constantly being developed.

Nice work Henry.

Sherwood

[sten gr]

Hello
What is the size on the spigot for the ø 89.5mm bore sylinder?
Same as the ø 90mm?

sten

[911 tweaks]

Henry... any update on your 3.5 build up ?? I thought this engine was to use your new super crank ??
I can't wait to see oics and hear about how it performs!!!!!!!!!!!! ;-)
Bob

[911 tweaks]

typo... fat fingers... 2.5 build here

[sten gr]

Me to, fat fingers.
I meant ø 89mm sylinder

[Henry Schmidt]

Originally Posted by 911 tweaks

Henry... any update on your 3.5 build up ?? I thought this engine was to use your new super crank ??
I can't wait to see oics and hear about how it performs!!!!!!!!!!!! ;-)
Bob

No news to report. This current economic situation he me scrambling much like so many of you.
I already build the corral for the pony that Obama promised, now I'm just waiting for my bailout money.
All kidding aside, this group of politicians couldn't be more wrong.
Whenever you medicate an injury solely to mask the pain you hamper the recovery.

Rant over, now back to engines and real would fantasies.