Laust Pedersen

As title

Does anybody know what type of pistons these are ?
Found in my 1988 951 non-S.

Laust

TRP951

They look like turbo pistons with valve cutouts in them, but then again im no expert. My stock turbo pistons look like that without the releif cuts in them.

inactiveuser92616

do you have cylinder liners in there? I see two different colors in your cylinder wall. If so, they could be aftermarket. Or maybe I am hallucinating and that ring is caused by the headgasket.

evil 944t

They look stock but with valve reliefs cut in. Do you have a big valve head? Are you the original owner?

Matt H

I agree they look like stock with reliefs crappily cut into them. Nice touch though!
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Laust Pedersen

And why would they have valve relief cut into them?
I have standard valves and cam.I have standard valves and cam … the mystery continues

Matt H

Someone probably had a timing belt break. The good news if it does again there should be no interference.
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evil 944t

My guess is the head was decked and they needed more clearance in the valve area.

hosrom_951

Laust: Those pistons are you're 'experimental' non-interference pistons you were working on a while back, if the timing belt snaps, the pistons and valves will not contact.....

Laust Pedersen

Hosrom, … BINGO !!

You have a good memory.

Here is a reference to the original thread on the subject.

I made a tool to cut these valve pockets with the pistons in place (In Situ) and cut them yesterday without spilling a single shaving in the cylinders, which still are in extremely good condition (only 2% leak-down on a 180k engine).

As a crude verification I turned the cam 360º with the head and cam housing stalled and the engine at TDC.

I did a few other minor things “while in there” and should have the car back on the street early next week.

Laust

hosrom_951

Laust: I was going to post a link to the thread, but i figures i better get in the car and get to work, besides i am half-awake anyways

Now, would this cutting cause and increase or decrease in compression ratio?? sorry if this was covered in the old thread, but i couldn't find it.

ibkevin

Excellent work Laust. How many cc's now in the top of piston?

There ya go again-creating a product that none of us will ever be able to live without.

Porsche-O-Phile

Fantastic job! Any idea what the new c/r is? Will they be radiused on the edges to avoid hotspots & stress concentrators?

Super-cool idea and great work!

Zero10

Haha, I knew exactly what they were when I saw the pictures, but it looks like I'm too late.
I remember this coming up over on Clark's Garage way back when.
Looking good

JimV8

LP thats excellent.