Tom M'Guinn

I just got off the phone with a highly regarded machine shop that has done a plenty of work on 944/68 motors (for dealers, racers, engine builders, etc.) They have the Sunnen machine and it was obvious that they know these motors inside and out. (He immediately suggested a cross-drill to help the No. 2, suggested piston squirters, quoted the piston to wall clearance from memory, etc.)

The shop tells me that they have run JE pistons (uncoated) in stock Alusil 944/968 bores many times without problems. He says they've done it for street and track cars and have never had one "stick" or take out a cylinder. Anyone else ever try it?

Geo

I'd get references.

Tom M'Guinn

Their reference list reads like a who's who in Porsche racing.

Geo

Specifically on this issue?

Start calling.

Tom M'Guinn

Well, I am not planning to do it, but was curious if anyone else has tried it. I wonder if we are just victims of Alusil-Mahle hype?

Chris Prack

Well we can buy a used engine as a group, buy some JE's as a group and have a pro wrench put the motor together. I would volunteer my time in teardown and assembly. We would make accurate measurements of cyl. diameter, out of round and taper, ring gaps, piston to cyl. wall clearance etc.

Then we would need someone to put the motor in a car and hammer on it for some period of time. An eight valve N/A motor is the obvious choice for this. Then periodically pull the head and measure the cylinders at the top looking for obvious wear or damage.

Between this list and the guys on the 928 board we should be able to make the individual cost pretty low.

It's an idea. It could certainly put the whole issue to rest.

Chris Prack

I just noticed that George has an 84 car that would be a good vehicle for our test mule. I have an 84 race car as well.

Tom M'Guinn

An idea like that needs a leader. I, of course, am much too lazy do lead the charge, but I would contribute some money if we could get enough others to share the burden.

JRMarchand

Hey guys, I have an issue with that too, one of these days I'm gonna put some sick JE slugs on a 944 and on a mid 70's 911 alusil and see...., well, If Chris can put this experiment (gig) together, I'll donate the racetrack, coffee and donuts.

Danno

How about combining this with the 944 engine-rebuild class that's been proposed?

Duke

I'm sure a complete teardown and rebuild on video would sell for some $$

OZ951

Hey Tom,

why not get in touch with some of those customers and see what they have to say? They may not want to talk tolerances but they may at least indicate if the pistons are satisfactory in alusil bores.

Brian Morris

I have to say I've never really quite understood the no Al pistons in Alusil bore thing. I guess the argument is you need hard against soft, iron against aluminum, but the alusil bores are hard enough for the rings to ride on?

--Brian Morris
89 951

TurboTim

It wont work.Galling will occur.

Danno

"I have to say I've never really quite understood the no Al pistons in Alusil bore thing. I guess the argument is you need hard against soft, iron against aluminum, but the alusil bores are hard enough for the rings to ride on? "

The soft part is the aluminium piston, thus the need for an iron coating on the stock pistons.