does any one why the 172 pistons all ways brake up around the exhaust port? I must have gone through 4 or 5 pistons on diferent barrels and always brake up. is there any thing that can be done or do i have to stop racing every thing on the road[:dance2:]
Just an idea and bear in mind I’m no Beerace but I was having problems with my Polini Barrel on aT5 motor, The jetting was a pain in the arse to sort but was almost there, nevertheless it nipped up 3 times, each time the score marks were around the exhaust port and each time it was carefully wet and dried.
I ended up getting an exhaust made up to suit the kit and overall set up and also to suit my needs ie. low down torque and a decent cruising speed. End result… No more seizes and a reliable motor.
And the good part is, the exhaust is left side, costed less than yer off the shelf Scorpions and Jl’s and sounds extremely nice. (looks like an old Mikeck)
As I said, just an idea…
If you find out, could you tell me!
mine seem to break inbetween the rings, I always thought it was because my oil seal leaked, and burnt the gearbox oil,as Ialways found a lot of carbon from the oil just above the breaking point, on the head,or wear on the rings causing the piston to slightly rub!
had three go,but I’m still useing the same barrel(i’m tight!)
Have you had the head reprofiled?[?
my head was skimmed by taffspeed. so have to move the timing a bit. forgot this last time and i went flying down the motorway doing about 85+(still running it in mind) head gasket went just before it holed the piston really pist off as it was a brand new piston. if you was thinking that 85+ plus is a bit extrem the motor is tuned to the limet in a cut down primmy frame with a massive upgear. once in fourth it pulls slowly but just keeps going.[[:O]]