Help in identifying pistons inside engine

[Gearby]

Has anybody ever seen these types of pistons before? They are inside a 2.0 engine I have and all that I know is they don't resemble the '65 to '67 standard piston as I have a set of those. There is some kind of logo or marking on the crown of the piston and the reliefs are an unusual shape. Sorry I don't have better photos but it was hard to even get photos through the spark plug hole. I suspect they're some kind of performance piston as the engine was rebuilt with S cams, but I really have no idea. Hopefully somebody has seen these before. The silver cylinder in the photos is a flashlight btw. Thanks in advance, Derek

[Olivier]

THey look like Hi Comp pistons (69S/906) but it's hard to tell. Maybe the experts can decipher the marks, but I suspect they are more related to a mass group than to a special model.
If you have an endoscope, you should try to reach the opposite side of the pistons, under the skirt so to speak. There should be a forging reference mark, and then you could ID them more precisely. (thanks to this forum for what I learned!!!)

Olivier

[larwik]

That looks like the "side" view of the "M" in the Mahle logotype...and #108..../Lars...

[beh911]

THey look like Hi Comp pistons (69S/906) but it's hard to tell. Maybe the experts can decipher the marks, but I suspect they are more related to a mass group than to a special model.
If you have an endoscope, you should try to reach the opposite side of the pistons, under the skirt so to speak. There should be a forging reference mark, and then you could ID them more precisely. (thanks to this forum for what I learned!!!)

Olivier

No expert but I agree 69S/906 based on the valve pocket relief. Different than 67S

[Frank Beck]

Yep. I would agree; 906.

Great pics.

Have you considered "moon" lighting as an arse spelunker? I believe there is a good market out there for cheap colonoscopy's.

[Olivier]

Yep. I would agree; 906.

Great pics.

Have you considered "moon" lighting as an arse spelunker? I believe there is a good market out there for cheap colonoscopy's.

For posterity, before it ends up in the bin.

[sithot]

More of the same.

Documented factory built racing engine. 2.0 with Chromal Cylinders and Ti Rods, 906 center oiler cams, boat tailed mains, mooned cylinders. The studs were insulated which was an attempt to control expansion/contraction issues. It did not work (well) as any moisture created stress risers due to corrosion. Nearly every one of them broke, that weren't already, when removed from the case. Used on the 911R as well.

[Olivier]

I've read somewhere (don't remember where? Maybe THE book about 911s by Bruce XXX) that this insulation is actually fiberglass. First used on 906s engines. This must be a very rare bit!

Sithot, wouldn't you tell us more about this particular engine? What kind of case? How's the Chromal coating hanging?

Olivier.

[sithot]

I've read somewhere (don't remember where? Maybe THE book about 911s by Bruce XXX) that this insulation is actually fiberglass. First used on 906s engines. This must be a very rare bit!

Sithot, wouldn't you tell us more about this particular engine? What kind of case? How's the Chromal coating hanging?

Olivier.

The Chromal Bores were perfect. It was built on an early magnesium case. The research was done by the new owner. I was aware that it was "claimed factory" when I got it but the owner didn't have any proof. The proof was on a bill of lading the new owner located where the sister
engine which was found as well, "one digit off". These engines were assembled with AT prefixes.

I've got lots of photos including the lightweight flywheel assembly. To see it sitting on the floor you wouldn't have mistaken it for a race engine. Had a set of 906 Mg manifolds for it too. He had sold the 46mm Webers years ago.

The Ti rods are not being used in the new build nor are the cylinders to my knowledge. The old rods are cool but a new set of Carillos is good insurance.

"Mooned" cylinder with bore shot.

[sithot]

Here is a rod, engine tin (different), and numbered cylinder (1-6)