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Oversize pistons vs liners and standard?

Mike Bohmann

Member
Joined
Aug 18, 2022
Messages
5
Location
Wisconsin USA
May need to rebuild the 4D95L engine in my Komatsu PC60-7. Looking at rebuild parts and kits online and puzzled as to the lack of oversize pistons. I believe this is a parent bore engine and it is still running so I don't anticipate anything beyond normal wear in the cylinders. I see some of the kits offered come with liners which I understand are "semi-finished" on the ID. Seems like a lot of $$ machine work as opposed to conventional rebuild bore/hone to fit OS pistons.
 

1693TA

Senior Member
Joined
Feb 27, 2010
Messages
2,687
Location
Farmington IL
Occupation
FAA Radar Engineer, (Retired)
Same thing. Liners are fit to the block and honed to fit the pistons.
 

Mike Bohmann

Member
Joined
Aug 18, 2022
Messages
5
Location
Wisconsin USA
I have rebuilt A LOT of engines, gas and heavier diesels going back 2-cycle Detroits. Replaceable liners are one thing, but HAVING to machine .090+ out of a block and installing what would be considered "repair liners" just to accommodate standard pistons seems like the hard (and $$) way to go. The only possible justification for liners might be the possibility of cavitation pinholes in the parent bore.
 

1693TA

Senior Member
Joined
Feb 27, 2010
Messages
2,687
Location
Farmington IL
Occupation
FAA Radar Engineer, (Retired)
Not disagreeing at all. However there are times you have to either repower, or bite the bullet. I've installed several "salvage sleeves" over the years to save an otherwise usable block. Cavitation holes are easily repaired with modern epoxy sealers and a salvage sleeve after the parent bore is glued up and bored to fit the sleeve.

Support for aging equipment these days leaves a lot to be desired.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
A PC60-7 is likely to be from the mid 1990s and will be a non tiered engine. Komatsu used to have oversize pistons for those engines but in all likelihood has stopped production of most all the parts for them. I have clients with old iron and dead engines growing blackberries over them because of parts availability. Exchange engines for that vintage stopped years ago.

Repair liners or sleeves as we know them in my area have been common practice on some types and brands of engines.
 

Mike Bohmann

Member
Joined
Aug 18, 2022
Messages
5
Location
Wisconsin USA
Parts, except oversize pistons, for the Komatsu 4D95 engine are readily available. Evidently that was a popular engine worldwide. It is just the "standard only" piston situation that has me puzzled.
 

Mike Bohmann

Member
Joined
Aug 18, 2022
Messages
5
Location
Wisconsin USA
I see some engine parts prices that look almost too good to be true. I'm sure it's all offshore, mostly Chinese. Any trusted brands/parts suppliers?
 

Tyler d4c

Senior Member
Joined
Mar 2, 2016
Messages
1,750
Location
Salix Pa
I see some engine parts prices that look almost too good to be true. I'm sure it's all offshore, mostly Chinese. Any trusted brands/parts suppliers?
Last year I rebuilt a cat 303 engine with a kit off ebay till it was done and proper it had genuine cat parts in it. In other words it was a 500 dollar and probably 40 hours or more time that i could have been doing something more better life lesson
 
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