Maximum conrod bigend clearance.

[curamrdan]

Hello, im with my mechanic just in assembling new engine. Local custom make rods for stroker went bit wrong, there is probably 50.62-63mm bigend diameter so in final we have about 0.09mm clearance on AAT crank (47.76mm pin) and new std KS bearings.

I know ACL and some others racing branded bearing are available with extra 0.025 oil clearance, which is almost our situation. But i dont know anybody run this much of clearance. Anybody have experience? Or may i throw rods into a bin?

thanks

[Error404]

Get them to make them again the right size

[andy10v]

Jeff/FRP suggest .0025 min, .003 for high power

http://theprojectpad.com/viewtopic.php?f=32&t=1370

[FCP-ENGINEERING]

clearance must be 0.04-0.05 mm normal oil, 0.07-0.08mm can be when used race oil bigger density 20w60.

[curamrdan]

Its for hobby driving, so as you noted(understanding andy numbers are in ft), 0.09mm is unusable at all. I just want confirmation, thank you.
Lets spend next money and waste another month or two, it start to be usual with my first audi build

[Error404]

You need to go with OEM dimensions on the big end otherwise your rod bearings will not fit. The correct big end bore size is critical - if there is not enough bearing crush due to too large a bore you will spin the shells = bottom end failure.
Oil clearance is taken it at the crank journal - between the bearing and the crank, not between the bearing and the rod. the bearing needs to be an interference fit into the big end.
Sure you can have custom bearings made but they will not be the special sputtered type used in our engines to help make them bulletproof and it will be a costly and complicated pain in the backside you don't need.
Copy exactly the OEM rod dimensions and just add extra length to suit your stoke & pistons.

[AndyP]

Copy exactly the OEM rod dimensions and just add extra length to suit your stoke & pistons.

Or just buy a set off the shelf from FCP Engineering or Sten Parner

[Error404]

Or that