ENDYN I use 4032 alloy on our normally aspirated pistons, unless the customer tells me ....

Hi there, Brian from Wiseco here. Sorry to hear your having issues with your Endyn pistons. Very commendable work doing research on the alloys though. Your descriptions of the alloys was first rate. You're smarter than most of our competition is I have some more info that I hope helps. Wiseco builds almost every sport compact piston w/ 2618 (unless specially requested by customer). All Endyn's are 2618. The reason for this is: to make big power w/ a small engine you either a: run a turbo, b: run nitrous, c: spin the be-jesus out of it. So we try to cover all the bases and go straight to 2618. 2618 does expand more than 4032 due to less porosity. We actually build the same clearance into the bottom of the skirt though as it only see's about 250 degre's of oil temperature.

We build the skirt taper of the pistons differently depending on the alloy and forging design. We do build two different primary styles of forgings. Strutted (like our IRL, CUP, Trans Am, etc.) -extremely light strong, but also so ridged that shape becomes very important; and slipper or full round (very similar except the band that goes out to the cylinder below the pin and heavier). These are more forgiving, but not as strong (this style is what the other piston companies sell as well). If you can furnish the part number from your box, I can tell you which forging was used. We offset almost all of our pins as well like the O.E's to quiet the pistons down. This is an expense that most of the other companies don't want to mess with, but for you guys running on the street, we've found it to be very helpful. I personally run the new 11.7:1 K566 series strutted piston in my own test engine and found them to be ABSOLUTELY silent on start up. I do not yet have 500 miles on it yet, which is the real test!, but I would expect them to develop a small amount of clatter on startup for about a minute, but certainly not to the extent you are experiencing. If you are running a slipper skirt or "full round", I would expect even less noise as we design those w/ less taper. I found the numbers for our pin bore clearance and Endyn's "usual" piston to wall clearance to be correct. Perhaps even a little to perfect which brings me to my next point. If the engine is taken apart yet, I'd HEAVILY suggest you have it taken to another shop and have piston to wall clearance checked again. Have them check taper in the cylinder bore as well. Measuring point is 1.300" below the oil ring groove on all our pistons. We've got a near constant problem of shops used to building chevy's putting in an extra "thou" of clearance knowing that it's better to rattle than seize. Honda's are a different animal though. If you go to another shop, they will likely give you the straight answer. Now, if you do find that they honed the engine too large, your only economical choice is to have the pistons coated to try and take up extra clearance. I'd recommend Polymer Dynamics in Texas at 713 694 3296 as they do many of the coatings for our Pro customers. Please give me a call at 800-321-1364 ext. 3177 if I can be of further assistance. Thanks, Brian Nutter-Wiseco Piston Co.