Can I use 95mm 3.2 (84-89) cylinders on my 78 sc 3.0 motor

[matty74]

Can I use 95mm 3.2 (84-89) cylinders on my 78 sc 3.0 motor.

If so what is the diff between 78 cylinders and the later 3.2 and whats involved in getting them to work with the 78 heads?

[Henry Schmidt]

3.2 cylinders are a direct replacement for 3.0 cylinders. No changes to the heads or case are necessary. In fact, with a slight change to the connecting rods you can even use 3.2 (95mm) Carrera pistons in a 3.0.
I would avoid reusing Alusil cylinders if possible, so make certain the cylinders you choose are Nikasil.

[matty74]

I was looking through Bruce Andersons book on page 148 top left is a pic of a SC cylinder with grooves for a ce head gasket, if you look on page 74 there is a 3.2 carrera Nikasil cylinder with no head gasket.


Just Double checking before I shell out $$.

Do the 3.2 cylinders require machining to fit the 78 SC heads?

If so there any impact on compression?

Help greatly apprciated

Cheers

matt

[tom1394racing]

Like Henry said...They are interchangeable with either SC or 3.2 heads. The only difference is the sealing ring, that Porsche disposed of with the 3.2 motors.

[matty74]

Thanks for you help guys

greatly appriciated.

cheers

Matt

[rbuswell]

Originally Posted by Henry Schmidt

3.2 cylinders are a direct replacement for 3.0 cylinders. No changes to the heads or case are necessary. In fact, with a slight change to the connecting rods you can even use 3.2 (95mm) Carrera pistons in a 3.0.
I would avoid reusing Alusil cylinders if possible, so make certain the cylinders you choose are Nikasil.

What slight change to the connecting rods are needed, Henry? Would the change require splitting the case?

Also, did they ever use Alusil cylinders in 3.2 Carreras?

[Henry Schmidt]

To run 3.2 Carrera pistons on a 3.0 crank all you need is a longer rod.
These rods can be custom ordered or you can just modify the stock 3.0 rod.
What is needed is .030" increase in the center to center rod length.
This can be accomplished by boring the small end of the rod with a center offset. Remember that the 3.2 wrist pin is larger 23mm vs 22mm for the 3.0.
Just offset the bore, install a larger bushing and size to 23 mm.
There are some mechanics that will remove the rods from a crank without splitting the case but I would never recommend this procedure.

There are two good reasons to use 3.2 pistons on a 3.0 crank.
First the longer rod improve rod length to stroke ratio creating an engine that spins easier.
The second reason is the cost for 3.2 pistons and cylinders is less. You can get high compression pistons for hundreds less than 3.0 pistons.

As for Alusil in a 3.2 Carrera, some US versions had Alusil.

[ChrisBennet]

Henry,
Can the 4 different tolerance groups (diameters) be ignored when mixing and matching cylinders and pistons?
-Chris

[Henry Schmidt]

Originally Posted by ChrisBennet

Henry,
Can the 4 different tolerance groups (diameters) be ignored when mixing and matching cylinders and pistons?
-Chris

Generally speaking tolerance groups should be respected.
When mixing and matching pistons and cylinders there can be benefits from mismatching diameter groups. For example: If you use a (1) piston in a (0) cylinder you can compensate for a small amount of wear.
If your question is about using a matched P&C with an incomplete set, I would say just watch the weight differences between the two different groups and try to limit the difference to 1 diameter group.
I.E. If you have five (0) group P&Cs and want to complete the set with a (1) P&C, I would say go for it (just balance all pistons first). If you a talking about using a (3) to complete a (0) set I would probably pass on that.

[rbuswell]

This is great! If I'm reading between the lines, there's no way to get the rods to a bore to drill out the larger size while they're in the case so the recommended procedure is to split the case. Sorry for all the newbie questions.

[jamesjedi]

Came across this old post. Very intersting. Can the engine be run on CIS, or does it have to changed to the later EFI or carbs etc?

[jeffery dalcour]

Would the same procedure hold ? Or is it not possible to use the 3.4 cylinders?
Jeff