Originally posted by ???
off topic but
a kid with a 6cyl VW of some kind dropped off a set of pistons hung on rods for the owner of the shop, i work at. to look at. i didn't get to hear what the customer had to say. just saw the box of pistons and heard that the motor was built at engine lab. (they were JE's) i was just wondering if you had any info on them.
just wondering cause jerry that builds all the fast DSM's was saying something about JE giving a lot of people the wrong specs. they were telling people to run .004 piston clearance and they needed more like .006. these looked like the same thing and i have a friend building a focus with JE's and they want him to run .004.
just sounds like he may run into the same thing. if he follows there intrusions.
there seems to be a pattern here
I think I know about the engine you are talking about except that the kid is trying blame us for his fucked up motor even though we machined the engine to spec and correctly assembled the short block.
If we are talking about the same engine all the thrust faces on the pistons were pretty galled which indicates it was not a clearance problem since if that was the case the entire piston skirt would be fouled up. Just the thrust faces being galled indicates that the pistons were being seriously overloaded or didn't get enough oil.
In addition to the pistons being fucked up one rod bearing was hammered so bad that it spun and all the others showed clear signs that they were also getting beat to death or didn't get enough oil.
Both these problems show that the motor was severely overloaded and/or detonated all to hell if its not a case of oiling problems.
Depite the switch to low compression pistons the kid claims that they were running no more than 6 lbs of boost and they did nothing more than let it idle for a little while and drive it around the block.
I am extremely skeptical of that story but my boss is being a lot nicer about it than I would be.
I asked the kid what he was doing about engine management and he indicated that he is still running the OBD I system and he didn't mention any mods to it.
My theory is that the kid thought some heavy duty low compression pistons would allow him to up the boost with no other mods and he learned the hard way it takes a bit more than that to try to seriously turn up the power on a VR6. Either that or they didn't put enough oil in the motor, assembled the oil pick up incorrectly or accellerated hard enough to slosh the oil away from the pump pickup.
Personally I think JEs get a bad rap cause their pistons are used in so many hi-po and race motors that they see a much higher failure rate than stock pistons normally do. One should not confuse failure from abuse with design defects or bad specs.
IMHO - .004 is the right clearance for a forged piston in an iron block. You could go with more but I would be worried about the amount of piston slap it would cause before the motor gets up to temp. The amount of piston rock it would allow could also lead to premature ring wear too.