OK, Got it.
See page 11B-23-5 of the 4M41 manual that you can find here
"Use a piston having the same size mark as that stamped beside each cylinder on the upper crankcase ..."
From the diagram it looks like there is a possibility for the different cylinders to have different markings because there is one location for each of the four cylinders.
It still does not explain what they signify and how you select if you rehone / rebore.
On page 11B-25-8 of the same manual it does refer to standard sizes for reboring.
11B-16-9 explains how to go about selecting the correct head gasket.
I would suggest that if anyone is considering rebuilding a 4M41 engine that they really need to download, read and understand what it says!
I presume those two pistons in the report weren't cleaned before taking pictures?
Either way the good piston showed that the engine had plenty of life left and that after 300'000km a tiny flaw in that bad piston eventually surfaced.
I presume the cracked side is the exhaust valve side that gets more heat than the intake valve side that gets some fresh air, so the piston will contract more on the cold side than the hot side, effectively pulling the crack open more and more once it's started.
Cylinder 1 might also see more back pressure as it is farthest away from the turbo hence more heat that stays on the hot side of the piston.
I think it was just bad luck with regards to a flaw in the metal on the piston and the age brought it to the surface.
Either way the good piston showed that the engine had plenty of life left and that after 300'000km a tiny flaw in that bad piston eventually surfaced.
I presume the cracked side is the exhaust valve side that gets more heat than the intake valve side that gets some fresh air, so the piston will contract more on the cold side than the hot side, effectively pulling the crack open more and more once it's started.
Cylinder 1 might also see more back pressure as it is farthest away from the turbo hence more heat that stays on the hot side of the piston.
I think it was just bad luck with regards to a flaw in the metal on the piston and the age brought it to the surface.
Andrew,
Please.... pretty please... send me the link to my 3.8V6 MIVEC motor as well. I tried to get it on my own, but the skills are not there
Please.... pretty please... send me the link to my 3.8V6 MIVEC motor as well. I tried to get it on my own, but the skills are not there

Guess what I got back Saturday 
CATS
Pocket is substantially lighter as well so lets hope this is the beginning of a new life.

CATS
Pocket is substantially lighter as well so lets hope this is the beginning of a new life.
HEY MAN!!!!
Is the old Snoopster purring again???
Are we going to see her Tie in a few Dots again this year??
Are we just as glad as you that she is back home again???
Is the old Snoopster purring again???
Are we going to see her Tie in a few Dots again this year??
Are we just as glad as you that she is back home again???
Congrats CATS.CATS wrote:Guess what I got back Saturday
Happy to hear that Snoopy is back home.
Thanks GentlemanRoelfleRoux wrote:HEY MAN!!!!
Is the old Snoopster purring again???
Are we going to see her Tie in a few Dots again this year??
Are we just as glad as you that she is back home again???
Yes I am very glad to have the Snoopster back. She is purring sweetly and I am giving her a bit of a gentle run-in period before I let her loose in the bush again. One or two small issues that I still need to sort out then she is better than ever before.
Roelf. I will definately try and make the Dots trip again. Now that I have my wheels back I can properly start planning. Will keep you updated.
CATS
That is all-round great news. T-I-D will not be the same without the Snoopy team there.
FANTASTIC!! Here's to the next 500 000+ trouble free kilometers!
2003 Mitsubishi Pajero 3.2 DiD
1996 Toyota Land Cruiser 4.5 GX
1996 Toyota Land Cruiser 4.5 GX
+ 1 gazillion!nielsch wrote:FANTASTIC!! Here's to the next 500 000+ trouble free kilometers!
Glad the pajero is sorted. Car trouble is not for the weak!