I have a Mazda MX5 MK3 2009 1.8 petrol car. The big end bearing went which damaged the crankshaft. I have a replacement crankshaft and I have measured the big end bearing which is 1.840 inches. Is this acceptable?
The Main bearings are :
Standard sizes for unground crankshafts are as follows:
Bearing Thickness = 2.504mm
Bearing Width = 19.101mm
Housing size = 57.018 - 57.036mm
Crank Size = 51.979 - 51.999mm
The conrod big end bearings are :
Standard sizes for unground crankshafts as follows:
Bearing Thickness = 1.504mm
Bearing Width = 16.599mm
Housing size = 50.025 - 50.046mm
Crank Size = 46.980 - 47.000mm
Thanks for the info it appears that the big end bearing should be min 1.84996 myn is 1.8400 this would be 0.0096 under. The person I bought it off is a mechanic who took it from a car which did not have any problem with knocking and he has confidence that the crankshaft will be OK. Not sure where I go from here 9 thou doesn’t seem a lot.
Ask if he still has the shell bearings as they should have the size on the back of them so you can match up a new set.
You can always buy some plastigauge to check its all OK.
OK thanks for the advise.
Have now bought the 025 oversized shells which should now be at the correct tolerance. Thank for everyone’s input.