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Sit N' Spin
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Discussion Starter · #1 ·
I'd like to get some input from the mahinists here on plasma moly rings in hopes of proving fact or disspelling rumor. Some guys seem to think that plasma moly rings have seating problems and take quite a few hours to seat, and claim that they'll never use moly rings in a performance engine because they've had nothing but problems getting them to seat. However I've heard from several builders that they should fully seat within the first heat cycle.

A couple machinists I know have said that it all has to do with the cylinder wall finish. I do know that different rings require different honing stones. If I remember correctly I believe since plasma moly is a much harder material that they require a very fine honing stone on the final hone to seat properly whereas chrome or cast iron rings need a courser one?

Also...is there a "proper break-in procedure" for seating rings in a performance engine?

Let's hear it from the machinists here.
 

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Jetaholic, that is total BS. Alot of people seem to think the MOLY rings are akin to chromemoly steel. WRONG!!!! The moly is not "mixed in" with the steel, it is a surface structure where the moly is virtually vaporized and sprayed onto the rings surface. The old moly filled rings (where the moly filled a groove in the rings face) took a little while to seat, but the plasma deals seat in a wink, if the walls are properly honed and the cylinder is ROUND!!!!!! The moly isn't on there thick enough to where away to suit the cylinder like an iron ring. And it isn't hard enough to wear away the 'peaks' of a coursely honed cylinder like a chrome rings. The moly won't wear in a smooth hone cylinder, and due to the fact that it absorbs oil to create a seal it is very gentle on the cylinder walls, they won't wear. So your cylinder has to be ROUND or you get the old "they never seat" story. Moly in itself is not hard. In fact it is considered "greasy" by metallurgists.



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Sit N' Spin
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Discussion Starter · #3 · (Edited)
Jetaholic, that is total BS. Alot of people seem to think the MOLY rings is akin to chromemoly steel. WRONG!!!! The moly is not "mixed in" with the steel, it is a surface structure or coating. The old moly filled rings (where the moly filled a groove in the rings face) took a little while to seat, but the plasma deals seat in a wink. Moly in itself is not hard. In fact it is
considered "greasy" by metallurgists.
That's pretty much what I figured. A friend of mine who recently built a 460 Ford told me he had nothing but seating problems with moly rings and pretty much blamed the rings as a result and swore up and down that he'll never run moly rings again. Come to find out, he hones his own cylinders the old school way (drill and a hone) and used a medium grit hone when he did it. Yet he strongly believes that the same hone should work for every type of ring and that the moly rings are junk as a result.
 

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Sit N' Spin
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Discussion Starter · #6 · (Edited)
Actually it was not a machinist that gave me the info about moly rings having seating issues. That was the friend of mine that I mentioned in my last post. The machinists I've talked to have always been in favor of them and explained that it all has to do with the cylinder wall finish and that you have to use a fine honing stone with moly rings.

Also, other boaters have said that their motors with moly rings have taken at least 5-7 hours of runtime to seat as well. This goes against everything I've been told by almost every machinist and engine builder I've spoken with.

Does engine temperature have anything to do with seating the rings? How about whether you run a PCV valve or not (i.e. introducing vacuum into the crankcase)?
 

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Moly rings need a VERY fine cylinder wall finish. Almost mirror finish. The reason is that moly has microscopic pores that make up about 60% of the face. A chrome ring has a little under 20% porosity for holding oil. That's the reason you need a rougher finish for chrome.
If you have a nice rough finish on the cylinder walls and a porous ring face you've got too much oil hanging around. Some of it will be left behind and burned.
 

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Gone
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You hone em 625 and then 3 strokes of an 800 and they will damn near be seated by the time you check piston to valve clearance and adjust the valves.
 

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Sit N' Spin
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Discussion Starter · #9 ·
Moly rings need a VERY fine cylinder wall finish. Almost mirror finish. The reason is that moly has microscopic pores that make up about 60% of the face. A chrome ring has a little under 20% porosity for holding oil. That's the reason you need a rougher finish for chrome.
If you have a nice rough finish on the cylinder walls and a porous ring face you've got too much oil hanging around. Some of it will be left behind and burned.
If I read your post right, I gather that instead of the oil hanging out in the crosshatch grooves in the cylinder wall like it would with the chrome rings, the oil hangs out in the pores of the moly ring instead?
 

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Break in?

You hone em 625 and then 3 strokes of an 800 and they will damn near be seated by the time you check piston to valve clearance and adjust the valves.
If a machinist tells you to baby and engine for break in, find another machinist. I fire an engine, adjust timing, and wring it's neck. Done deal.

We ran an engine at Long Beach that had less than a minute run time because we finished it in the pits that morning.........Didn't have time to set up the "pit water". Launched the boat into the first heat and ran it until the following April w/o teardown. A quick check of the end clearance, and back in for many more heats after that. We only get accused of "killing bugs" when a piston turns over in the bore.......Ray
 

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steelcomp was here
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LOL...I just wrote this in my response to Tim on the "break in oil" thread...

Tim, what you did was fine. It's a little agressive, but the best way to break in an engine is take out and run it good and hard. Valve springs are more critical than rings...I think valve springs really need to be brought up to operating temp, and then allowed to cool before really romping on them. Your ring seal may have gone away for a few reasons, but my first guess would be cylinder wall finish. There aren't many machine shops that really pay attention to the details when finishing a cyl wall, and it can make a night and day difference. Moly rings really don't need much breaking in...heck, they're about broken in by the time you push them in the cyl's, but the finish can have a big effect on how long they last.
JMO
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If I read your post right, I gather that instead of the oil hanging out in the crosshatch grooves in the cylinder wall like it would with the chrome rings, the oil hangs out in the pores of the moly ring instead?

With a chrome ring there's very little room for oil so you have to have some tooth to the cylinder wall to hold oil. With moly rings there's room to hold oil so you want the cylinder wall to be smooth and hold less oil than "normal". What you don't want is to give oil two places to hang out (and moly rings don't like rough finishes)

People that use moly rings with a rough crosshatch are the ones that say moly rings take forever to seat.
 

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Sit N' Spin
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Discussion Starter · #13 ·
With a chrome ring there's very little room for oil so you have to have some tooth to the cylinder wall to hold oil. With moly rings there's room to hold oil so you want the cylinder wall to be smooth and hold less oil than "normal". What you don't want is to give oil two places to hang out (and moly rings don't like rough finishes)

People that use moly rings with a rough crosshatch are the ones that say moly rings take forever to seat.
That's about what I gathered...you just worded it much better than I did :D

Your last statement...that's pretty much what I figured. Just wanted to make sure my opinions on it were correct.
 

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Many,many years before all these fancy tool, we used to mix bon ami with gas and poured down the carb to break in the rings, worked too.
 

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Many,many years before all these fancy tool, we used to mix bon ami with gas and poured down the carb to break in the rings, worked too.
I have a 1953 Caterpillar D-8 dozer and in the service manual under engine re-building, that Bon Ami trick is a Cat approved method of seating rings.

Jim
 

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steelcomp was here
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I have a 1953 Caterpillar D-8 dozer and in the service manual under engine re-building, that Bon Ami trick is a Cat approved method of seating rings.

Jim
Well, yeah, back in 1953!;)
I saw Bill Jenkins one year sprinkling a little magic (BonAmi) dust over the tops of his carbs during a warm up in the pits.:)devil
 

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Living in a cage of fear
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You hone em 625 and then 3 strokes of an 800 and they will damn near be seated by the time you check piston to valve clearance and adjust the valves.
Bingo!
Try to run plasmas with out honing with a plate and you can see the out of round on the walls.
 
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