I have a block I want to use with some stock pistons (4g63). The manufacturers specs. call for a maximum clearance of 1.5thou. To get the bores round and nicely honed I will need to carry them out to 3 thou. Now I have heard of people using coatings to adjust the clearance within the manufacturers original spec. range (Mike for one), but this is a bit different as I would be using the coating to build up the piston size by 1.5 thou. or more. Has anyone ever done this with success or am I stuck with going with aftermarket pistons?

I guess that would be based on how that coating is designed to be used. If the coating manufacturer says that you should be including the coating thickness with your piston dimension measurement, then maybe you can give it a shot. On the other hand I don't think you'll find many skirt coatings that add up to 1.5 thou thick for the two skirts.

Cast pistons are kind of forgiving though. Especially buff ones like the 4G.

Eric, you touched on the other question I had. Am I likely to experience any problems with running the clearances at 3 thou vs. 1.5 thou (i.e. not using a coating?). I assume ring seal would suffer, but would cylinder wear be excessive? High oil consumption? Any other problems?

Thanks guys.

In most cases you are suggested to compensate for the coating however most coatings wear off and the "added" clearance given when measured with the coating can become an issue later on.  I measure my pistons with coatings and set clearance where I want them regardless due to the nature of the coating burnishing down to a zero clearance. 

The coatings I use and apply myself require no added clearance are 100% the substraight once applied and cured.  This is unlike most other coatings offered on the market. 

Posted By Wrecked on 03-09-2010 05:12 AM

Eric, you touched on the other question I had. Am I likely to experience any problems with running the clearances at 3 thou vs. 1.5 thou (i.e. not using a coating?). I assume ring seal would suffer, but would cylinder wear be excessive? High oil consumption? Any other problems?

Thanks guys.

Nobody has tried an OEM piston with higher than spec. clearances? Not even with a junkyard daily driver engine?

 

I have seen some hard ano pistons that made a mess of the bore, a Honda Bonneville K motor was the victim.  Considering you are building up a layer of aluminum oxide on the piston, it might have issues.  Some of my piston engineer friends from a very reputable company say that its a big no no.

Posted By Eric Hsu on 04-01-2010 02:30 PM
Yeah I have. I used stock Civic Type-R pistons in my LS engine way back. Piston to cylinder wall clearance was about .0025". It burned about 1/2 qt every 2500-3000 miles, but was otherwise okay for 12,000 miles before I sold the car.

1/2 quart, I guess I could live with that. Thanks.

I figured you would say something like that   Here is the thing though, for the past four or so years I have been running a N/A 4G63 in my car with Evo 8 pistons/rods etc. (turbocharged of course). The N/A  block doesn't come with squirters and it has held up fine all this time.