I am putting together a 440 with Mahle file fit plasma moly rings. My questioin is what would you guys recommend for the cylinder hone. I have a access to 320, 400, and 800 grit flex hones. I was under the impression that smoother was better with plasma moly because you don't need the "roughness" to hold oil on the cylinder wall like you do with cheaper rings. What would you guys suggest?
Thanks in advance!

320

It's a combination of rough and fine with a plateau finish that works best. If what you have is no longer good enough due to wear I'd have it done professionally. 320 is way too rough for a bore finish. Just run iron rings and prepare to break it in because the moly will simply be torn off the rings.

What does Mahle say? They'd be the experts on their own rings.

R.

I called Mahle ' s tech line and they said they have seen no significant difference in seal or longevity within the 320 to 800 range. They said to ask my preferred builder for their recommendation. I am assembling this motor as well as one for a friend and plan to buy my own hone from the 3 new ones available to me listed above so hone wear is not an issue at this point.
Thanks for the comments!

Good info BradH, but can you elaborate on the plateau finish? I thought that was what the flex hone created. Do I need a different finishing brush after the hone or does he mean to start with a 320 hone and then finish with a finer hone?
Thanks so much for the help!

A plateau finish takes off the high spots created by the original honing stones. That portion is normally taken off by the rings, hence the break in period. Without removing this high surface you risk ruining the moly surface. And to make matters worse, it almost always needs to be done properly with a machine that can control the pressure and stroke of the stone.

320....just run it forward and reverse...If it makes you feel better about it a Scotchbrite finisher will knock off the "high" spots...then you can brag up your "plateau" finish. Way more important is to make sure the bores are squeaky clean when finished.....

NO. To be specific, the words "plateau" and "Brush" are associated with Brush hones.

What was meant by what the machinist said was to finish hone with 320, then run a Brush ball hone through the hole to produce the plateaued surface.

Go to http://www.brushresearch.com/literature.php?type=2 and read the tech articles and you'll see what I mean.

R.

Thanks for the clarity. I already had it machine honed at the shop to the proper bore with (I believe) 320 stones. I was going to finish it with a ball hone myself. I think I was doing what you suggest I just wasn't using the terms properly. That being said, I think I'll use the 800 for the plateau finish over what the machine shop did.
Thanks again for all the replies!

i manage a machine shop and machine blocks for a living as well.if your machine shop finished the bores to size properly you shouln't touch it other than to clean it before assembly.it sounds like your not sure what they did? i suggest that you give them a call and go over it with them before ruining some potentially good,finished work.