JS Motorsport Pistons/Rods First Impressions

As I said I was not complaining. The engine was a touch stronger with the higher compression JSM setup. Only reason I tore the engine down when it had the JSM parts in it was I wanted build the engine with the alloy barrels while I could still do it.

I figure if I live long enough I'll put the JSM rods and pistons back in the 750 engine. If the standard 750 bores in the Molnar barrels aren't already too large for the JSM bore spec I'll get new standard bore JSM pistons with the thicker coating. I did think about doing that from the get go with the Molnar barrel change, but I had already purchased the other long rod kit, so figured I'd use it to see how it worked.

Fast Eddie said:

The last two engines I built (920 and 1007) had JS pistons with the thick coating as described an above.

I liked the notion that it beds in to suit the bore as you describe Jim. They were both built for track use so we’re gonna have a hard life.

Neither engines have been stripped since, so I don’t know what the pistons look like now, but all external indicators are still good. I’d definitely use the same in future

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The piston alloy on the JSM pistons didn't get scuffed at all.

With some aluminium alloys, the oxide coating is very tough. It can be created by cold anodising, however stronger aluminiums often contain copper and cannot be successfully anodised. It requires a manufacturer's decision about which way to go, and a customers' decision about whether they want strength or wear properties. Jim Schmidt is probably smart enough to get a good combination for general use. I suspect most pistons these days are spin-cast and forged, so they would all be pretty good. Some of the pistons which were made in Australia years ago, were terrible. They used to seize and get filed several times before they became stable.
Mahle pistons have always been excellent - light and strong.

Got these in and installed. Love the way the DLC looks in this light, just blends in with the background. I honed the gear bushing and then coated the bushing with a dry film lubricant and honed the coated bushing again to fit. The dry film lubricant on the DLC spins like a high quality ball bearing in light oil. Rocker shafts should be here in a week or two along with some other stuff I am testing.

I posted a photo of the head and pistons coated in another thread, should have them back by early next week as well.