Info needed on current engine setup.

[Cairns888]

Firstly I need some info on the current setup of my engine. I purchased the car as it is. I have read a few books about engines but I none the wiser.

What I understand (which may be wrong) is that most short stroke engines are built using 3.0 litre cases.

Anyway my specs are below.

2.0 litre aluminium case (1965)
2.8 litre RSR barrels and pistons (Mahle)
2.4s heads

So I calculated 2.65 litre displacement.
And with 92mm pistons and a short stroke of 66 mm

So lots of questions and would appreciate any info

- is this a good engine setup?
- looking at upgrading the induction from 40 IDT webers to PMO's. 40mm or 46mm ??
- any idea of the compression ratio?


My personal opinion it is a strong, high revving, lots of low down torque, (
Which could be because of the low weight of the car of 830kgs) info from PO.

Ignition setup is an Mallory type which will be upgraded shortly to most probably an MSD setup.

Thanks for you help

Jim

[Cairns888]

Anyone?

Any info would be appreciated.

Thanks

[CamBiscuit]

Hi Jim

- is this a good engine setup? Yes! People use the later cases as you dont need to bore the spigots, and they have piston squirters etc already.
- looking at upgrading the induction from 40 IDT webers to PMO's. 40mm or 46mm ??Why? what don't you like about the Webers? You can play with the IDT's a fair bit from what I gather. Paul Abbott from Performance Oriented has some good writeups on Webers.
- any idea of the compression ratio? Depends on your pistons and if the heads were machined. Do you have any paperwork to go with the engine? Assuming it is sungle plug then the CR is likely to be under 9.5 (or so) :1

What sort of driving are you intending with the car?

Cheers

[Cairns888]

Thanks Cam.

No paperwork with the engine at all. Purchased the car basically sight unseen.

Very honest seller.

PMO carbs will be an option as my carbs need a full rebuild and when pulled apart I will make a decision either to do a full overhaul with Performance Orientated or start fresh.
Webers are not original for my car.
Yes single plug.

Car is street / track days. Nothing serious.

It is hard finding info about my engine and why it was done that way.

Thanks for your input.

[Harvey Weidman]

What I understand (which may be wrong) is that most short stroke engines are built using 3.0 litre cases.

Anyway my specs are below.

2.0 litre aluminium case (1965)
2.8 litre RSR barrels and pistons (Mahle)
2.4s heads Jim

That IS the original "short stroke" (66mm)
The 3.0 SS (70.4) designation is used to tell it from the 3.2 Carrera (74.4) "long (er) stroke"

Great engine BTW
H

[Cairns888]

Cheers Harry.
So even the short stroke 3.0 is 70.4 mm not 66mm. So the 2.0 case short stroke is the shortest stroke available?
If so it is all making sense.

[Harvey Weidman]

It all came about when people started putting bigger pistons on the 3.0 and made it into a 3.2.
The "short stroke 3.2" description was used to differentiate it from the stock 3.2 found in the Carreras with the long (er) stroke.
And yes, the 66mm stroke is the shortest production crank...race cranks went down to 60mm as I recall.
H

[Flieger]

I think the 1.4 liter 935 (for the 2.0 equivalent class) had the shortest stroke of any of the Porsche 6's, bar the F1 V6 possibly. I think it was less than 60mm. The 956 may have had the 60mm or else it was 66mm.

[Cairns888]

So using the 2.0 case was for strength and a 66 mm stroke without any mods. That would or should mean it has piston oil squirters??? Also why would 2.4 s heads be fitted instead of 2.8 rsr heads. Perhaps price and availability or solely for performance. I have seen pics of rsr pistons and they have a massive valve rebate on them. I might have a peak with a camera soon.

[Cairns888]

Has anybody else built a similar engine?