bones427

I'm building two motors and need to know what to set the main + rods bearings to 1st is a 511 bbc with bme aluminum rods this is a drag only engine max rpm around 7200 , 2nd is a 391 stroker sbc with mgp alumn. rods street strip car. bme recommends .002/.0025 min clearence mgp says .003/.0035 on the rods what would be best and what should i set the crank to. Thanks!

billhendren

With aluminum rods cold clearance will be tighter than steel rods.the cold clearance you use depends on what oil temp the engine is going to be at when raced and the weight of oil. If for example if your going to run 150 deg oil take a rod with a bearing torqued to spec and put it in an oven @ 150 deg.pull it out and measure the bearing bore and subtract the crank size,this will give you the running clearance. we set it at .0025 with light weight synthetic oil or .003 with 20/50 at this point you can ignore the cold clearance.Bill