Well a few weeks ago I blew the diff in my car anyway long story short I decided to tear down the motor in my car fo ***** and giggles really. Well turns out at .0055 pistons to wall clearance its was still a little tight b/c there was a good amount of skirt rub. Now I have GE sleeves now depending on the mettalurgy of the cast they use it may expand slower than some other sleeves. Now we are running .0075 clearance (however this is a race motor and we had to go a little bigger to clean up out of round bores from the shitty machine shop I used prior) After talking to my new machinist (who knows his **** and very credible) We think about .0065.007 clearance should be sufficiant Ross tech told me .005-.006.

Next thing we ran into is that the pin fit is too tight and the ****** pin hole was out of round between .001-.002 in some places (Some due to being ran in the car but not all)

to recap:

Ross pistons need a lot of clearance at least .006 but probably better with .0065-.007
- also the pin fit is too tight and pin bore is out of round.

Just a little info for those running ross or thinking about running them. I still believe Ross are great pistons. Any good machine shop can fix these up good just have them check the **** first.

 

it seemed like alot of clearance to me at first as well but ross tells me .7 would is perfect

 

You have your logic ALL wrong. You are running that motor way too lean. That is why the aluminum is on the cylinder walls. The problem with the pins is from the detonation caused by running to lean.
Without seeing your piston, I'll bet that the aluminum galling is worst right under the oil ring and gets less as it goes down the piston. If the piston was too tight, it would be worse at the bottom and get better going up.
If a piston needs that much clearance to operate, it is not designed properly.

 

.0065 to .007 seems to be a litlle loose for skirt to wall clearance..do they expands that much ?

stan

 

We had 5thou ona Ross Motor...and there was no noise at startup...I thought it was going to diesel like a bitch.