piston clearance

stage 10 4.310 bore arias pistons older bae fuel head
172cc chambers 45 psi boost 9200rpm
new piston 4.303
new clearance is .007
how loose can you run a piston
i have a bunch at .011-.014
thanks

 

watch your skirts.Dave

 

.007 is not enough....a little too much won't hurt you......011-.014 should be ok
measure directly across from the center of the pin
just my 2 cents

 

I'am with Darren..also good talking to you to day Darren..I will call you to see if you got you new mill..later Dave
www.myspace.com/daveloweswr

 

.002 to .003 is perfect. BAE recommends that the sleeves be changed @ .005.

 

Depends on where the piston is measured. If piston skirts are not collapsed, there will be some taper on them. Usually .002-.003" with the skirts measuring larger at the bottom of the skirt. See where the manufacturer wants the pistons measured and go from there...... .007" below the oil ring could be .004" at the base of the skirt and vise-versa.
I've noticed some manufacturers are touting running their pistons tighter, when really all they are doing is having you measure the piston closer to the bottom of the skirt......

 

Let me clear something up. Where a piston manufacturer wants you to measure the skirt is just a reference point. It's so it's measured at the same point every time. There are thousands of different cam shapes available. It all depends on the application and the forging being used. There are some cams for naturally aspirated and others for supercharged applications. Yes, some manufacturers run their skirts tighter, but it's not based on where it's measured, it's based on the cam profile (shape). Some manufacturers require running loose clearances because they are in the stone age and haven't done any FEA analysis to see how much room for expansion a piston really needs. The tighter you can run a piston, the better the ring seal will be, the more power you will make. If my pistons are at .011 to .014, It's time for new pistons and/or sleeves. And if I new what the skirt was supposed to measure at any particular point, I would more than likely find out the skirts are collapsed.