Wrist pin circlip upgrade

[pampadori]

Anyone offer a piston wrist pin circlip upgrade that uses the kind with the rings on the ends that you use circlip pliers with to compress? Like this:


My last engine build was a nissan 2 liter that revved to the sky and it used this style making life much easier. I'm curious why Porsche doesn't use them and if anyone here has any experience converting to them.

[db_cooper]

I think the "wire" style clips are lighter (not a bad think on a piston moving at high speed and reversing directions..less chance of coming loose)..and more fiddly to remove for sure.

I don't know of a conversion part number or application for the circlip with eyes.

[Dmitry at Pelican Parts]

Hi pampadori,

I also have not seen or heard of an upgrade to the oem version. In case you need one, I've attached a link to our catalog. Best of luck!

1983 Porsche 911 SC Targa - Pistons and Cylinders - Page 2


-Dmitry

[prschmn]

Factory pistons are made to use a wire type clip. You absolutely must stick with that.
A square cut snap ring is NOT going to stay in the factory groove.

[pampadori]

Ok. The wire clip is what I'll use. But I feel like adding some loops to each end so you could use the pliers would result in a better mouse trap.
I'm still not sure why a circlip like the picture wouldn't work just fine. Perhaps it has to do with the shape of the groove it resides in within the piston isn't flat and is round instead. But if it works reliably in other engines with faster piston speeds, I remain skeptical it wouldn't work in these old lumps.

[db_cooper]

The original piston pin wire style clips are/were used on most euro air cooled engines including the 911 and most motorcycles..have to say I have not seen the big "C" eye clips used in an air cooled engines at all. It may be a high heat and piston speed design thought.

I would not try and re-engineer that critical part.

[prschmn]

Circular cross section requires a continuous ring-putting tangs on the ends precludes that.
How often are you going to remove and install anyway?

[Tippy]

You're playing with fire putting a square-edged C clip in place of the round wire clip.

'Taint worth it!!!

[db_cooper]

Originally Posted by Tippy

You're playing with fire putting a square-edged C clip in place of the round wire clip.

'Taint worth it!!!

Absolutely, and insure the "gap" on the wire clip is either at the bottom or top, looking at the piston. This forces the wire clip deeper into it's groove as the piston changes direction at TDC and BDC when running.

[chrismorse]

The retainer must be engineered to transmit any axial thrust from the pin to the piston. This requires that the pin end and the mating surface of the retainer be engineered to also work together.
I have no way of knowing this but I am fairly sure that end clearances between the pin face and the retainer are also critical.

To paraphrase Carroll Smith, "Nothing good has ever been said about a retainer failure"

Scary Stuff,
chris

[uwanna]

Many years ago I bought a Jaguar XK140MC that had had higher compression pistons
retrofitted to it. Shortly after the purchase, it starting burning a lot of oil and running rather poor. I tore it down to find the PO had installed the new pistons using the type of
retainers you show in the photo. The retainers had eaten out the retainer boss, came loose and deeply gouged the cylinder walls. Had to overbore the block and install new pistons. To sum it up DON'T even think of ever using that type piston pin retainer!!

[Quicksilver]

The "hot trick" for reliable use of circlips in a high performance environment is to use two of them on each side of the pin. You install them with the openings in opposite directions so they overlap. Each inserted so the rounded side faces each other and the flat side faces out.

Not sure how this is an upgrade for a Porsche...
The reason that anyone uses them is it facilitates fast easy tear down which is important if you are drag racing, running circle track, or ...

Spirolox or the simple round wire retainer may be a pain to tear down but they are much more reliable.