Ross piston clearance

[turbodave231]

I'm honing a stage block to accept a set of custom Ross pistons and I have a question for anyone who has used Ross in the past.

The Instruction sheet calls for .007 wall clearance as a minimum for normally aspirated applications. It calls for .010 for blown gas or turbo applications. These pistons have a barrel design and don't have long skirts.

I've never used Ross before and a wall clearance of .010 sounds huge to me. I'm concerned about ring seal and cylinder wall loading at the bigger clearance. All the Ross guys are at PRI and I can't talk to them until Monday.

Anybody have experience with Ross pistons? Please share!!

 

[49-blues]

I bought my ross pistons from-Andersen Performance also who i would ask about Ross pistons.

 

[Mac in SD]

My machinist told me back when, that Ross's reeeelllly expand and need a lot of clearance. In other words, noisy.

 

[turbodave231]

Thanks for the replies. I'm going to call the Tech guys at ROSS on Monday. They expand that much? Must really sound horrible at cold start-up. But my customer can live with that.

Dave

 

[STP]

Dave, my Ross slugs aren't that noisy on cold startup..Solid roller makes more noise..Me and one of my bestest buddies (Leo) decided to tighten them up to .008...About 15 1/4mile passes and a half dozen 1/8 only passes in the mid to low 6's on the engine with no issues.

 

[turbodave231]

Just to finish this thread. We got with Ross and landed on .007 piston to wall clearance. The pistons have a thermal barrier coating on the tops and the anti-friction coating on the skirts. Less heat in the pistons and less friction means we can run them a little tighter.

 

[STP]

Good deal Dave...I forgot to add that Calico coated the tops and skirts of my slugs. Did you get a couple extra when you ordered from Ross? I went ahead and purchased a set of 8 just in case I hurt one...

 

[GARY HARVEY]

Something else that helps pistons...

beside getting them cryo'ed would be to have the rings coated too.

Maybe one day Jerry will find a place to put a cryo machine....

 

[turbodave231]

My customer placed the order for the pistons, and he forgot the ring support rails..........but I always get at least one extra piston, just in case.

These piston have a copper colored thermal coating and the black friction reduction coating. Very nice looking pieces indeed!

Here are a few pictures of the motor mocked up.

 

[Dominic]

Why are the valve notches upside down? The eyebrows are supposed to be on top right?

Are those pistons installed upside down?

 

[Dominic]

I sure hope you read this before you finish assemble that engine. Those things are installed upside down.

 

[GARY HARVEY]

Coatings

Interesting that the thermal barrier is cocoa colored, not up to speed on this since all I've ever seen or used, ended up being a very light grey that would polish to a nice light luster. As to the skirt coating, Du Pont Indusrtial Black Teflon (non food Grade) was used as a base with Moly top coat.

Anyone interested in how to do this undoable process email me and we can visit. :biggrin:

 

[turbodave231]

Good eyes!!

Wasn't paying attention to the piston orientation. Pistons aren't installed on the rods yet, I still need to pin fit the pistons and rods. Pins are just in the pin bores to check block to rod clearance. Did you notice the brass tube in the oil pickup? That took me awhile to get done.

 

[Dominic]

Good eyes!!

Wasn't paying attention to the piston orientation. Pistons aren't installed on the rods yet, I still need to pin fit the pistons and rods. Pins are just in the pin bores to check block to rod clearance. Did you notice the brass tube in the oil pickup? That took me awhile to get done.

Cool glad you cought it! You did say you were mocking it up so i figured it was not a finish assembly i also noticed you had no rear main side seals in the cap too

I just built a 3.8 stage and i had to do something similar to what you did with the oil pump pickup, i like your idea too it looks great! It looks like a long stroke is it 3.625? Those look like Carrillos too, looks to be a really nice piece you're putting together!