Time for first oversize or not?
Posted: Fri Nov 04, 2016 5:27 pm
Hi,
I was discussing this week with a colleague about oversize pistons.
His opinion: As far as the cylinders are not out of spec (56,4-56,42 is standard, wear limit is 56,5mm) he would give the cylinder a fresh hone and put in a new standard piston.
My RD has 40000km with the first pistons in close to perfect condition but I think they are already out of specification.
Cylinders are not measured up to now but I think i will take them to the company next week and ask if they can measure them.
I pulled the cylinders because the front Power Valves were stuck, otherwise there was no need to disassemble the engine. It was running quite nice.
If the cylinders are still below 56,5mm what would you do with this one?
It`s the only scratch I found on all 4 cylinders and I can feel it clearly with my finger nail (I hope not too deep for +0,25mm which is only 0,125mm in radius, not really much).
Would you ignore it and put a set of standard pistons back in it? Or should I search for one cylinder which is at the same wear level as the other 3 and put this one to my 2 other "oversize needed" cylinders for my second engine?
By the way, the specifications are a bit funny in the service manual.
Piston clearance should be 0,06-0,065mm, standard piston is 56,39-56,4mm, standard bore should be 56,4-56,42.
This would mean on a new standard engine there is a piston clearance of 0,00 to 0,03mm
I was discussing this week with a colleague about oversize pistons.
His opinion: As far as the cylinders are not out of spec (56,4-56,42 is standard, wear limit is 56,5mm) he would give the cylinder a fresh hone and put in a new standard piston.
My RD has 40000km with the first pistons in close to perfect condition but I think they are already out of specification.
Cylinders are not measured up to now but I think i will take them to the company next week and ask if they can measure them.
I pulled the cylinders because the front Power Valves were stuck, otherwise there was no need to disassemble the engine. It was running quite nice.
If the cylinders are still below 56,5mm what would you do with this one?
It`s the only scratch I found on all 4 cylinders and I can feel it clearly with my finger nail (I hope not too deep for +0,25mm which is only 0,125mm in radius, not really much).
Would you ignore it and put a set of standard pistons back in it? Or should I search for one cylinder which is at the same wear level as the other 3 and put this one to my 2 other "oversize needed" cylinders for my second engine?
By the way, the specifications are a bit funny in the service manual.
Piston clearance should be 0,06-0,065mm, standard piston is 56,39-56,4mm, standard bore should be 56,4-56,42.
This would mean on a new standard engine there is a piston clearance of 0,00 to 0,03mm