Piston to valve Clearance?

[turbotalon1g]

Aren't you supposed to rotate teh piston so its backwards on a DSM because of this reason?

[gvr4]

NO!

More important than the location of the valve reliefs is the 1mm offset on the wrist pin. That is meant to reduce piston slap and reduce the forces seen by the crank as it passes TDC. If there wasn't an offset, the cylinder would fire at exactly TDC, when wrist pin, crank pin, and main centerlines were all lined up, and for an instant, all the combustion force would be transmitted directly onto the mains. If the offset is backwards, piston TDC is achieved slightly before the crank reaches the highest point in its rotation, so when the piston fires, it's almost like trying to rotate the crank backwards for an instant.

[JET]

All this work and you are putting incorrect pistons in the engine?!? Seems crazy with how cheap aftermarket pistons are for these engines. Stock 2g pistons probably would work better in the long run.

[gvr4]

I believe you have that backwards. I'm putting the right pistons in the wrong car.

[Pushit2.0]

So take a die grinder, wiz wheel and make the valve relief bigger. I did not know evo motors had offset wrist pins, funny how they slap like crazy and wipe out cylinder walls.

Check my build thread for exact specs but the short list: 1mm over valves, MAP stage 5 head, GSC beehives with .050" shims, stock oil passages and stock Hla's and cam followers, Crower stage 4 cams with adjustable cam gears, degreed in at I -4 E-3.

[gvr4]

I hadn't heard that part about wiping out cylinder walls either... Ahh well I'm only at .02" over. I'll go wiseco if this build doesn't last...

I already re-checked my clearances and I'm sure I'm good to go. Otherwise, I'd just stick some 40 grit adhesive backed sandpaper on the valve, and grab the stem with a cordless drill. Cutting valve reliefs isn't that hard.

[Pushit2.0]

The couple motors I have torn down the middle/ bottom of the cylinder walls on the thrust side had a lot of scuffing.

[munchgsx]

How are you measuring your clearance? How much as been milled off the decks? Is your TDC height above the current deck? If so how much?

[gvr4]

The best I could do was with a dial indicator on the valve retainer. I moved the crank a degree or 2, and lifted spring pressure off the lifter til I could feel the lash adjusters spring max out so I new I was at 0 lash.

I'm not sure on the block deck number, .007 was milled off the head this time, but I don't know how much has been taken off in the past.

Piston is .055 in the hole at TDC.