Can anyone tell me what are the common causes to scuff a cylinder?Piston tops look perfect but the walls have light scuff marks on them.

 

How come you've got the heads off that 05? Just wondering.. You doing some head porting or something?

 

It had a slight miss and failed a cylinder efficiency test.Dealer thought it was a injector changed it ,still failed ,then checked the compression,#5 cylinder was low(310psi) so they pulled the head and it has a scuff in it.#6 & #1 were barley noticeable but 2,3,4 had light scuffing but nothing you could feel with a finger nail.

 

A number of things will "scuff" the cylinder.

dirt in the air. Not really a scuff though.
an overheated piston
fuel in the oil + high temps
wrong piston/cylinder sizing
debris in the intake air, like filings.

What kind of scuff are you talking about ? Pictures ?

Are you stock or modded ? I see your posts about shimming fuel regulators, twins, etc. Is that on your truck ?

 

The #5 cylinder scuff is opposite the exhaust port and runs about 1 inch wide.The other cylinders have scuff marks in various spots.I had a lot on my mind today when I was looking at them so I can't remember exactly where but it looked like it was enough to take off the cross hatch in certain areas.I will try to get some pics but I am not sure on how to post them.

 

I posted image posting instructions here.

Twice actually, if you can't understand the first time, look at the second one.

 

Wet stacking from prolong idling??

MikeyB

 

I've seen scuffing/bore damage from piston rings installed incorrectly. I don't know how that can happen from the factory but nobody is perfect.
Especially that you mention the problem opposite of the exhaust valve as that's where you normally have an endgap of a ring and they do tend to rotate somewhat in the bore which would give you a wider path of damage. JMO....

 

Can you explain "wet stacking"?

 

It's when the combustion chamber temps drop and not all the diesel is burned. Coats the cylinder walls with unburnt diesel fuel.

MikeyB

 

How many miles do you have on your 05' ???

Seems like you've already "put her through her paces" for a "newer" truck.

Sure hope you let her break in properly...

 

A mild case of coolant mixing with oil can also cause the scuffing you describe. I have seen this on Volvo highway truck and off road diesels, as well as Mack units. Just a bit of food for thought.

 

It would sure be nice to know what happened to blkdually's engine.

 

Any chance any of your options caused the issue?

"2005 3/4 4x4 Q.C. S.W.B.,Auto,T.S.T.Quadzilla downloader,BD Flex Plate,D.T.T. race tranny 89%Converter,pro-52 turbo,F.A.S.S. "

I was reading in another thread about EGT's and thought of the box you have. What kind of EGT's did your truck run with the mods?

 

Guys, Given the location of the scuffing, I'm thinking excessive unburned fuel in the exhaust combined with excessive EGT's. J.Davy what were your maximum EGT's? Did you ever have any high egts and black smoke. ks