7.3 Bore wear with Clevite Mahle plasma moly rings

[elrodalexander73]

I am posting pics of bore wear on a 50k mile engine I had built with head studs, comp 910s and Smith Bros' a while back. The engine was removed from my wrecked F350 and I am in the process of adding a cam and resealing the engine to put in my 95 I have purchased. There appears to be minor scuffing and scoring present. I made note that when assembling this engine with the bores honed to 320 grit the rings began to instantly score the cylinders. I had made several phone calls to different builders and all said run it. Engine took 3 full oil changes to break in and had almost zero blowby and oil consumption at time of wreck. I first removed exhaust manifolds and found zero evidence of oil ever in exhaust ports. Stem seals were doing their jobs and no oil on base of valve. My question here is does the plasma moly cause irregular wear patterns that are much different than the original factory rings. This engine was so tight that even at 30 degrees F. you needed no glow plug assistance to start engine. I used FFD 250/200s and tuning from G.H. and PHP and egts were never sustained above 1100 degrees F and a few bouts of 1300 degrees horsing around. I will post pics in next reply box.

 

[elrodalexander73]

Pics of bores and heads. No ash build up on valve faces and dry exhaust ports

 

[MeTo]

I have seen that before. The guy needed to trim (file) the ring end gaps and didn't chamfer the edges. Did you do a compression check before disassembly? Was assembly lube applied before the piston and rings were installed? What type of oil was used in the engine? Have you contacted the ring manufacturer?

 

[gnxtc2]

How do the pistons look like? Was the blocked bored/honed prior to getting pistons or were the bores sized to the pistons received?

Three oil changes to break in a boosted motor????

Billy T.
[email protected]

 

[elrodalexander73]

What I mean by break in is the oil consumption virtually stopped. First 3 oil changes engine went through 1 qt to 1.5 qts. I haven't removed pistons yet. 15/40w oil was used to coat the skirts and I measured all ring gaps.. Every single piston ring was gapped. And the scoring when assembling was in various areas of the cylinder. I had made note that the rings were exceptionally hard. The rings are a real dark compound type coating. The engine at the time of tear down and inspection used no oil. The extra fuel did turn the oil a little blacker than I had liked but the engine had zero blow by steam at all which is surprising. I wish my dumbass could have taken a video to show you guys at operating temp. The exhaust ports show no signs of oil residue and the valves as you can see have no white ash/ oil build up. I am calling mahle clevite today to ask a few questions in Novi Mi

 

[elrodalexander73]

Block was bored .020"', bored approx .017" then finish honed and pistons fit to bore to set oil and skirt clearances.

 

[golfer]

(from my engine guys)

I would guess that the bottom of the cylinder was probably left sharp after the cylinders were honed which leaves a razor edge that cuts into the piston as it rocks at BDC, which will pull pieces of cylinder and piston and get trapped between rings and cylinder. If it was happening during assembly then the block probably wasn't cleaned well enough. It is hard to tell how deep the scoring is so it might not be that bad or it could be bad, don't know. The worst thing would be that there isn't enough ring end gap and the rings are butting up to each other, don't think that is the case cause that normally turns out way worse a lot faster

 

[elrodalexander73]

I wiped everything down with paper towels and starting fluid and used paper towels as a reference to see if any residue was still present.. I rehoned block as soon as I saw the scuffing and tried again with same results. Was not scoring the bottom part of the skirts. Block was cleaned with hot soapy water and wrapped everytime with plastic wrap when I was done working on it for the day.. Heads were hot tanked and inspected very closesly. Honestly I am floored cause my ring caps were within spec.. This thing had no blowby and no oil consumption.. I look at the bores and say how the *** can it be.

 

[Swaan]

If its everything you say it is as in no blow by or oil consumption plus starts as good as you say then run it.

Geez, it is what it is. Why did you tear it down anyway??
Sounds like it was perfectly healthy.

Oh i see you just wanted to re seal and cam change.

I would just run it. 50,000 miles is nothin

 

[TARM]

Have you contacted the ring manf?
The dark coating you mention sounds like nitriding i.e nitrocarborizing basically a form of case hardening that can when put thru a polish process give a very low friction surface as well. I could be completely wrong that is what it is though as well. I have only personally worked with it in firearm manf.

 

[elrodalexander73]

I contacted Mahle clevite yesterday (1-800-223-9152) and they said if oil consumption was not present as well as lower amounts of blowby present then run it.. An old machinist for grooms said that may have been the heat transfer of the plasma moly coating that caused the cylinder walls to look like that.. I'm at this point of buying rings and honing it.. Then haul it up to swamps and see what they say.

 

[TARM]

If its going to bother you and always be in the back of your mind I would say do what you mentioned just to give you peace of mind. It may seem like $$ to do it but that stress over wondering everytime you have any issue etc maybe well worth it.

 

[IdahoF350]

You've got plenty of replies, but more can't hurt. If the scratches catch your fingernail or a dental pick, it should go to a machinist. If they don't, it's not abnormal to have visual lines of travel in the bore. Keep in mind, the crosshatch causes the rings to spin, but the pistons are fixed (non-rotating, only reciprocating).

You said you re-honed as soon as you noticed the marks during assembly. Did you power hone or do it by hand? Does your machinist use a plateau hone (or finishing brush) to remove the sharp peaks left from the honing stones? Did you do the same when you re-honed?

Also, motor oil on piston skirts and rings relays break in or ring seating by glazing the cylinder walls on initial start up. There isn't enough heat in the combustion process even on a diesel on initial startup of a new engine and that oil turns to carbon and fills the valleys of the hone crosshatches. It can take several thousand miles to get enough heat into the glazed oil to remove it and allow the rings proper lubrication and proper ring seating. I've used WD40 for 15 years, Total Seal has a dry powder lubricant for their rings, and you may get some other engine builders to chime in on their preference, but using motor oil just slows the break-in process and makes you wonder why you consume oil for a while.

Point being, proper cylinder finish, and correct assembly lubricant, and you'll seat the rings with minimal wear in the first hour of run time, just like the latest engines from the factory.

 

[gnxtc2]

Best way to break in a boosted motor.....start motor, verify no leaks and go beat on it. Boost pressure forces the rings into the cylinder walls. There is nothing else to break in on these motors.

Billy T.
[email protected]

 

[gwunter]

Cross hatch causes the rings to spin?? That's a new one to me.

 

[fastersteve]

Best way to break in a boosted motor.....start motor, verify no leaks and go beat on it. Boost pressure forces the rings into the cylinder walls. There is nothing else to break in on these motors.

Billy T.
[email protected]

True for all engines. Warm it up, then go twist it's tail...