? about TRW .030 pistons

[TURBOTIMMER]

I took my block and pistons to the machine shop after 400 miles of oil blow-by. I checked the ring gaps and everything seems ok there, so I thought there was a problem with piston wall clearance. The guy at the shop tells me there's between .004-.0045" clearance. TRW calls for right around .004". That also seems ok. The problem is that the pistons are rocking in the bores so much, that the rings aren't seating. The only reason I can come up with is that the pistons are expanding enough to grab the pins when they get hot from boost.

I'm I even close here, or do I really not know what the f&%$ I'm talking about? The pin ends looked good when I pulled the motor back apart. Anybody else here ever have a similar problem? Please speak up. I want this thing back together ASAP.

They are TRW forged pistons with the stock heavy pins that come with em.

 

[xlr8ngn]

Sound like alot of clearance. For some reason I was thinking TRW's were max .0035". Anyway, what is the hone like? What kind of rings? Was a torque plate used when bored. What did the bores look like when you took it apart?

 

[frankg]

Bad valve guides in the heads can cause blow by also, thats if everything else looks good. Frank

 

[TURBOTIMMER]

The bores are scuffed opposite of the pins. The rings used were perfect circle .030 over molys. I never checked with TRW on the clearances, but the machinist said .035" was the minimum they called for.

I'm not sure on any of this, but in the future, this stuff will be handled by someone that builds these motors all the time. I have alot of money and time tied up in this thing, and for what? So I can put a couple hundred miles on it and have to tear it back apart? Not any more. It's not worth it. I have much more fun in my stock motored GN. Its much more reliable, it can take alot of boost, and its consistant.

This motor is going to someone who knows what they're doing, not someone who makes a living doing machine work on small block chevys.

 

[Spongebob]

Sorry to hear that Tim...

Did you try Hemphill?