head coming off again

[Peter Connan]

the worst wear appears to be on the sides of the bores (as opposed to front/rear) is that correct?

If so, I think Frans is correct.

PS, next time you build an engine, use the thickest oil you can find. Wynn's (and no doubt some others) have a specialist "assembly lube", and that's the right stuff.

[Andre Steyn]

Yes peter, you are right its actually concentrated to right under the precomp chamber on al six no damage on the front, back or exhaust side. The big issue now is to find out exactly why this happened. Cos there is no point reasembling with repaired bores if the main cause still exists in the machine, unfortunately the block has to come out anyway for I need to either replace the sleeves or piano wire to get the sleeve protrusion fixed.

[ricster]

That's good news that the pistons and rings are fine !!!!

Maybe Frans can give some info on why this happened, or what can cause it to happen. Could excessive idling cause a heavy carbon buildup?

If the pump is not pushing the correct pressures, could the atomization of the diesel in the precom be not igniting properly and making lots of carbon that is then packing around the piston?..... Frans .... Frans.... Waar is jy ???

[Michael]

Andre, is it possible to measure the ring gaps and post the measurement? I found these measurements in a manual and would like to compare it to yours
It is for the TD42T engine

PISTON RING GAP
Standard ring gap: mm (in)
Top ring
0.30 - 0.45 (0.0118 - 0.0177)
2nd ring
0.50 - 0.65 (0.0197 - 0.0256)
Oil ring
0.25 - 0.45 (0.0098 - 0.0177)
Max. limit of ring gap:
1.5 mm (0.059 in)

[Andre Steyn]

Right, everything measures within spec only thing not in spec is sleeve protrusion. What now! The real cause of the scoring is still unknown. So as things stand its new sleeves, pistons and rings, this time alfin and keystone! TD27T pistons! From alert so again autopower brand. New bigends and mains a head gasket from nissan and head bolts from nissan to, unless someone has a quality cheaper option or 3. Injectors and pump coming out tomorrow to have them checked and recalibrated!

[ricster]

Still doesn't make sense to me.... fact.... there is scoring on the sleeves. What can cause that if everything mechanical is within specs. Was the intake manifold, intercooler, turbo and connecting pipes perfectly clean? I'm thinking that some small "stones" or metal chunks got blown into the cylinders and wedged between the sleeve and the piston, and possibly dry sleeves on initial start up. I can't see the carbon buildup scoring the sleeves.

You won't go wrong with the Alfin rings and pistons. The only thing to bear in mind is to drive the motor, otherwise those rings don't expand out and seat against the sleeve.... more compression ( in otherwords don't idle the motor for long periods of time.... even when running the motor in) .... more the ring pushes out.

Running it in must be like driving it normally. Obviously don't race through the gears or race it when cold, but pull away normally and then put your foot flat and go through the gears. Keep the revs below 3000rpm for the first 300-400Km and after that normal driving required. Again don't idle that motor for longer than 2 mins. Those rings don't like that

[Andre Steyn]

I'm also worried as to why, the guys at sac centurion say according the pics its a fuelling issue. But I did the pump and injectors! And as far as my knowledge goes all intake bits where perfectly clear of any bits and pieces. So guys I'm out of possible causes. So ja block's coming out again!

[Andre Steyn]

Even the big enginering guys where stumped as to how its possible the bore can be so badly damaged but not the piston, and this on all six, the same place under the precoms where injection happens!!!

[Tinus lotz]

Mabe the sleeves were "soft" krisis I will really want to find out what happend here????

[Andre Steyn]

I would definately also like to know, I honestly don't want to redo everything after this anytime soon, Tinus I wonder if your not perhaps right about the sleeve material being soft but on all 6?. Cedric who did your fuel pump and injectors and the dyno work, and what rear wheel horsepower did they manage?