Cab - Did you happen to look at how thick the skirts are w/ your Ross vs. your Diamond pistons? My Ross are fairly thin in that area, which makes me wonder if they're trading off weight for skirt stability.

biggest problem with skirt scuff on ross is people not deburing lower bore tears them up, id coat skits with dry film and tops with ceramic if you can aford it. swain has been doing nascar(nutcar) stuff since the 1970 here in new york. it helps but costly

Had issues with a few pistons in different motors getting scuffed , one issue was bottom of cylinder bore was'nt de-burred , the other was a tight gudgeon pin............ran .007" piston to bore clearance on the 605" , these Ross pistons would scuff pretty bad , never thought it to be the manu fault , those pistons hung out the bottom of bore & rocked like crazy , don't think any film of oil would of helped those pistons.

Measured a couple of the pistons today to see how much they'd changed due to wear-n-tear and my having "scrubbed" the heck outta the skirts w/ ScotchBrite to remove the scuffing. Both had "shrunk" about .0007" compared to the original Ross spec sheet dimensions for the set (e.g. 4.3745" now vs 4.3752").

I think the cylinders picked up about .002" w/ the re-hone job, which puts the clearance in the .007-.008" range. Ross' instructions say to run .004-.005", but also mention that engines honed w/o torque plates will require additional clearance (although they don't specify how much more). Due to circumstances beyond my control, the re-hone on this particular block was done w/o plates, so I may not be as far out on clearance as it looks.

Given the semi-budget nature of this rebuild, I'm thinking I'll pass on the skirt coating expense at this time and just run 'em as is.

.007"-.008" on Forged piston, race motor.... run it, it will be fine, might slap a little more on cold start but other than that, you'll never know.

I agree with several others that skirt coating is kind of a joke/$ making scheme. Piston top (thermal)coating is about only one worth ever thinking about.

I had a W2 dirt track motor come in shop late last week, guy had 2 spare new pistons for it (JE's) & I saw it had some "home" coated skirts... I mentioned to him, I'm sure that coating probably did'nt survive too well as it's kind of a gimmick, & was a waste of time. Got motor apart & sure enough, not much black coating left on any of the skirts, pretty much completely wore off & that is short stroke long rod piece (3.578" Stroke, 6.40" rod)

See it all the time, even with well done factory coatings by Companies like Mahle & Wiseco on their Pro-Tru's... it just does'nt live forever & is more of a sales ploy than anything.

Instead of wasting money on a coating I would invest in having the skirts hard anodized, it is a bit costly but a much better bang for the buck, holds up very well and makes more power...