alanoo said:
Wiseco themselves recon they would use 90 to 100µm for non drag engines.
Truth is Wiseco are known to have a cheap design and expand more than other brands forged pistons... as always, you get what you pay, and Wisecos are cheap forged pistons 🙂
Now you tell me. :roll:
alanoo said:
Ring gap is what I guess explains the oil consumption, not directly the noise; and I think the noise is a dead bearing due to oil starvation, but it might well be something else (but honestly I will say there's a 90% chance for my theory cryb.. )
I'm pretty sure that will be the cause of the failure. Initially, the noise only seemed to happen between 2,500rpm and 3,000rpm. Obviously got worse but would disappear when I dipped the clutch, which at one point made me wonder if a flywheel bolt had sheared off and was rattling around.
Clearly, I can't check that the machine shop did the rebore to the exact thousandth of an inch but I've no reason to doubt them, based on their reputation. I gave them the Wiseco spec sheet and left them with a piston whilst they did it. Trying to remember the exact clearance requirement but think it was something like 30 thousandths of an inch, so are you saying that the ring gap that they did was maybe larger than the spec? If so, wouldn't that mean that anything rebored to a 90 to 100µm clearance would have the same kind of oil consumption issue?
The car has kicked out a cloud of black smoke from the moment it was re-assembled. Due to it being black, I'd always assumed it was over-fuelling judging by the state of the exhaust. Indeed, when it went back to Courtenays for them to check, it was running rich on part throttle through the midrange. Maybe it was "burning" so much oil it was black and not blue, although the exhaust residue smelt of petrol and not oil.