[G_Don]

Originally Posted by Patrick L.

You have .023" clearance ?

Where were you taking the piston measurements ? It should be taken on the thrust surfaces.

I took the measuremnets at the top of the piston right above the top ring. I'm assuming this is not the thrust surface. Where is the thrust surface? I tried googling it, but it was still unclear. I will be sure to re-measure the piston when I get home from work.

Originally Posted by Dave in MN

Gordo,
The piston you show looks like it started seizing in the cylinder. Many piston manufacturers suggest .002 to .003" clearance and for a solid skirt piston, that is too tight. I usually hone to .0035" for a street engine and .004" for a performance engine that will be worked hard.

Thanks for the link! Good stuff on there! I heard 0.0035" from a guy I know. He said to get the pistons and then hone them accordingly, and that I could have a little more clearance than what is typically recommended.

Originally Posted by Tom Wesenberg

The top of the piston runs the hottest, and has the least amount of oil, so I'm not surprised at your piston scuffing.
Did the engine ping?
Did the engine overheat?
I saw a good running engine wipe out the pistons like that in a couple miles of pinging.

The engine definitely had a higher pitched, irregular noise when I would run it. It had no rhythm in relation to the engine, kind of sporadically Id hear a "ping". The engine overheating and smoking while driving was the initial start of this whole problem.

Originally Posted by Jim Brierley

As John says, it is unusual for pistons to seize at the top, and as Dave says, you need more piston-to-wall clearance. Start with a new set of pistons, bore or hone cylinders and start fresh. I bore a stock engine to .003" clearance, then hone another .0005", more on performance pistons. You can safely bore to 4" if you want. Back in the day Ford said .002" maximum, that is way too tight with today's pistons.

Would it be best to purchase a new set of pistons that are 0.080" and hone it or just go to 0.100" and have it bored. I guess it couldn't hurt anything, other than my wallet to get 0.080" pistons and hone the cylinders, and if anything goes wrong, have a professional bore the cylinders to 0.100".

I was consistently getting cylinder measurements under 3.955", roughly 3.953" to 3.954" with the telescope gauge and mic. Would it make sense that the cylinders were too small, and the pistons (with 0.080" etched on top) were 3.955" and wouldn't have enough clearance in the cylinder?

I did hear that boring to 0.100" gets really tricky, i.e. the cylinders' walls are too thin.


Thanks so much for the help guys.