ThomasC2

Hi all!
A friend of mine has opened up his engine (3.6l 964-92) because of a retainer broke, but it happened at idle so no real damage. It was also time to replace some gaskets and other stuff. It’s a low mileage car so the inside looks as new with no visible marks, scratches i.e.

But we got into a discussion about how important it is to install the cylinder heads on the same cylinders he dismounted them from. He will change the oil/piston rings and they are the only things that moves against the cylinder wall, so should it matter? He'll send all the parts of for a clean at an engine shop and that’s why we started to talk about this.

So which parts can you mix, and absolutely NOT mix?

1. Cylinder head and cylinder?
2. Piston and conrod?
3. Piston to cylinder?
4. Conrods position on the crank?
Thomas

Undutched

This may or may not help you.

as I am rebuilding my 90 C2 I have done the following:

GT3 4.0 crank
LN Cylinders 102mm
Pankl reinforced steel rods in Gt3 size
Custom JE pistons (to fit the rods)

Most things can be mixed and matcked. I could probably get away with GT3 rods and just have custom pistons (no extra charge), but since I'm going Turbo I need some stronger rods.

You can also use 993 Cylinders and heads AFAIK, the same goes for the internals. There may be things that need to be modified, but I haven't heard that parts don't fit. You need the right combo. I.e. if you take that crank, you need to take the fitting rods and the fitting pistons.

Rocket Rob

I defer to the engine experts on if its a good idea to mix and match. I seem to remember reading that the 993 head exhaust port studs are 90 degrees off of the 964 heads so if you change heads you will need to change/modify your exhaust.

ThomasC2

We not talking about doing any changes here. His question is just how important it is to put all the parts back in the exakt same order as they were. Meaning, does the head from cylinder 1 have to go back on to cylinder 1 with the conrod and piston from cylinder 1? Or can he put the head from cylinder 3 on to cylinder 1 if he lost track on how everything was before the tear down?

Thomas

Rocket Rob

When I rebuilt my engine, I numbered all of the parts and put them back in the same positions, just to be safe.

Undutched

Removing them may not be as important. But once removed a certain set of parts, should be kept together, so that the bearings, rings, etc. fit!

So it is easier to number them from the start and keep the together when changing bearings, etc. rather than be confused halfway!

ThomasC2

I think the confusion is already done, at least to some extent. That's why he needs to know how big the problem is.
Thomas

Steve Weiner-Rennsport Systems

1. No problem, however keep right & left side heads on their respective sides for the HE's to fit.

2. No problem.

3. This one IS a problem. The piston and rings match the existing bores for ring sealing so do not mix these up.

4. No problem. The rods should be re-sized with new bolts and new rod bearings.

ThomasC2

great info, thanks!

Thomas

Navaros911

On point #2 I read somewhere it is good to balance the total weight of the pistons and the rods. So that the sum of the two in weight is as close as possible to the others.

Can't remember where I read this... I think it was in one of Bruce Anderson's books.

Not that I'm an expert, but if it is not a problem to mix rods and pistons, I would do this since it costs nothing and won't hurt.

Undutched

That is a nice to have, not a must, since on a stock engine this isnt the case. You are right though. Since they are already out, might as well do that, since its a small cost factor now.

hockenheimr

Every-time I see GT3 crankshaft mentioned on here people are saying how cheaper it is then a 964 one. If I look up the prices, they actually seem pretty expensive....like north of $4gs....am I looking at the wrong thing?

Steve Weiner-Rennsport Systems

$2440 for a GT-3 crank. All of the air-cooled ones are almost double and nowhere near as good.

robt964

What are the key differences between the two cranks Steve?

hockenheimr

Thanks Steve, much better than I thought, any idea of the going price on a GT3 oil pump?