Stuff you learn here…
What’s the advantage? Think I’ prefer Teflon buttons (never used those either).
My best guess is that it has a benefit to production cycle time, and probably reduces the potential for engine failures under warranty, related to poor installation of a circlip. Although, SOME “performance” rods for those engine do stick with the arrangement, so it can’t be all bad either.
You also now only have one critical tolerance to maintain (pin to piston), rather than two. The tolerance on the small end of the rod can probably be pretty wide open with this arrangement.
Teflon buttons are used in lieu of circlips, and would be of no benefit to this arrangement.
Yes, was just saying I think I’d prefer them to a fixed pin, but I follow the logic now, thanks. Buttons wouldn’t work on my stroker anyway. The skimpy slipper piston bosses are far narrower than the bore so the steel pins can be shorter and lighter.
Saw my machine shop do this tons (IIRC, SBC rods used that scheme) and never saw any issue with it.
Teflon buttons are da BOM! Used those in my Datsun racer, out of a healthy fear that, at near constant 7000 to 9900 rpm usage, even spirolox could vibrate loose.
Yes, I believe Chevys use it to…but I don’t like to talk about them 
The only “issue” I can see with it is the need to press them out, and the possible “trauma” that could cause to the rod. But, decades of re-using rods seems to indicate that’s a non-issue.
I used em cause I had less confidence in my engine assembly skills and was afraid of what might happen if I didn’t get the circles in right.
I hope you guys test the fit at room temperature first. Having either the pin/conrod or pin/piston fit even the slightest bit sloppy would not be good.
just a thought. Have the rods reconditioned and resized but note if you are planning on using upgraded rod bolts at a different torque you need to tell the machinist this. Also supply the rod bolts with the rods so they can be torqued and then resized.
My Mahle pins differed by a bit less than 1.0 gram. I swapped them around to more accurately balance the pistons and the pins all fit just the same, needing only a short heat with the hair drier to slip in. They’ll float just fine as the Aluminum hole will expand more than the steel pin - so you’re comment on a little, tiny bit snug is thermally sound.
The bit about the stamped “flash” on the circlips is covered in some assembly manuals and makes sense. I found the advice and followed it. I’d guess there are shops who don’t go into this detail. MAybe it makes no difference, but it made sense to me.
The original pistons differed by a maximum of 6.0 grams, Mahle’s by 5.0 grams.
Uhhh, I’ve never seen a setup like that. The wire circlips I’ve seen had tangs for you to get a tool on it to install or remove it. Such a tang would prevent a bevel on the pin from even touching the part of the clip that sits in the groove.
Which establishes what? That you’ve never worked on race two strokes? Not really. The pistons I just fitted to my stroker are the same. A small boss cut away to let you pry them out with a pick (one use only) and the rest is the lightest and most secure design where any side thrust merely secures the circlip even tighter. The kind you describe add reciprocating mass to a critical spring that you definitely don’t want fluttering open/closed with ears ser perpendicular to piston travel.
They are fine as flat UJ circlips with no reciprocating forces.
Google Kramm-Lox, and prepare to have your mind blown.
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