Piston pin retainers?

[RedCoupe]

After dealing with the wire-type circlips used on Mahle pistons as well as the fat wire circlips used on JE's, I can't help but wonder why other retainers aren't used that are easier to remove and replace. Are the wire circlips superior to internal snap rings? Surely it's not just to save a few pennies. (BTW, years ago I helped my late father overhaul an airplane engine in the home shop, and those big 5 inch pistons used internal snap rings to retain the piston pins.)

[TibetanT]

Hello There:

I asked this question a while back about the Ross Spiral Lock type clips since a friend (machinist) wanted to know why I did not use them in my engine build.

The answer I got pertained to the way the channel on the piston itself is engineered/made. Looking closely at the Mahle or KS pistons you will notice that the channel the clips sit in are rounded, so the Ross Spiral Lock type which is squared-edge will not work for our application.

Also, as some knowledgeable engine builders here have pointed out, if Porsche race engines have used these circlips in their respective Race Cars for years winning at places such as Le Mans, why would I question that experience.


If you search my posts, you should find some answers to your question.

Hope this helps.

[Walt Fricke]

Well, J&E might get more business if they switched to circlips. An order of magnitude easier to R&R than the spring clips. Even the Mahle clips are easier to use than the J&E. And that's even if you use the Stomski tool. Be easy enough for them to change how the channel is made.

The fact that the Porsche clips work in a racing environment is not really a testament to their superiority to other methods. They work well at their job. Something easier to R&R might work equally well. And they are a lot easier than the J&E clips.

[safe]

Its not that difficult to remove and replace the Mahle type clips, even without special tools. Maybe the JEs are worse.
How often do you replace a piston in an engines lifetime? Ones every 30 years?

[RedCoupe]

Ed and all,
I realize that Porsche Mahle pistons are designed for the wire type circlips, and other types of circlips or snap rings won't fit properly. I just wondered why they (and JE) chose this type of retainer as opposed to other more user-friendly retainers. Yes, I have the Stomski tool for installation of the wire type clips, but one can't help wonder why.

[m42racer]

Its a safety thing. The pins can bang against the clip and you do not want a sharp corner where a heavily loaded part lives. Pins shouldn't act as a slide hammer, but the Piston manufacturer doesn't know how well the rods have been repaired, so all caution is taken.

[Walt Fricke]

The J&Es are an order of magnitude more difficult to deal with then the Mahle/KS ones. If it is a race engine, rebuilds may be on the order of every five or ten years depending. A stock class 3.0 will go a long time shifting below 7,000 RPM. A 12:1 Compression modified 3.0 shifted at 8,000 RPM or maybe 8.5 or 9 is going to have to be gone through a lot more often.