Piston pin/rod bushing clearance???

If you run a vacuum pump you may want up to .0015.

If your using Ross pins in the Ross pistons I believe they recommend .001 or more for N/A gasoline motors drag racing. I would open them up a little more on a street/strip motor on the rod to pin clearances, .0010 to .0013. I went out to my shop and looked at several sets of instructions for Ross pistons in my motors, the instructions do not make any reccommendatios on wrist pin clearances Both sets of instructions are for Ross custom made pistons, Ross does not include the wrist pins with thier custom made pistons, you have to order them seperate and pay extra for them Try taking one of the pistons, if you can, and measure the wrist pin bore at room tempature and then heat it up in a oven for twenty minutes at 200 F and see how much the wrist pin hole grows or schrinks

my machinist set mine at .001

A rule of thumb you can remember that will never get you trouble for clearance is .001 for every inch of shaft..This holds true for wrist pins of near one inch to locomotive cranks with 8" of journal diameter...

Thanks for the input and help guys. No instructions on rod/pin fit. They only said that they "may need to be lightly honed" (this is from Ohio Crankshaft, rod mfg). Ross only says to lub them slightly with lubriplate.
I ask my machinist what he set them on because of nothing in the instructions, he said .0003". Seems to fit OK, but I was thinking that .0003" was too tight. I'll talk to him this week and verify.
Thanks, Brian

.0003 is way to tight I'm assuming this is a full floating wrist pin,not press fit is it? ask him how much clearance you have for the rod bushing to the wrist pin and how much between the pistons and wrist pins Also ask about how much end clearances between the end of the wrist pins and the retainers( minimum .001 IMO) The end play should be enough to be felt with your finger stuck into the wrst pin pushing it back and forth while holding the piston in your other hand or in a rod vice

CaB,
Pistons have double spiro locks, and I haven't attempted those yet. But I'll check them for sure.
Pins came with pistons, I felt like they were an OK fit. Will check that as well. Thanks, Brian

Brain, I wouldn't, and don't, use grease on wrist pin installation. Use the oil your going to run the motor with