What should the rod to floating pin clearance be?

[brads70]

Just measuring the clearance and I get .0012" to .0015" seems like too much to me? 

[Chryco Psycho]

I do nto have that spec in my head but it sounds close to me , you need a little room for oil & heat expansion

[brads70]

I do nto have that spec in my head but it sounds close to me , you need a little room for oil & heat expansion

Thanks! I sure hope it's right. I was just under the impression it should be like .0005" as it gets bigger/more clearance as it gets up to temperature?

[72cudamaan]

typically it is .0006-.0009 Brad.  Should feel like a slight thumb pressure press fit.

[brads70]

typically it is .0006-.0009 Brad.  Should feel like a slight thumb pressure press fit.

    That's what I was thinking? hummmm maybe time to phone Muscle Motors....

[jimynick]

I'd call the piston manufacturer Brad. They should be able to  give you chapter and verse. 

[brads70]

Just reading Muscle Motors web site ...they say clearances should be .0008"  to .001"

[PlumCraZRT]

You sure your micrometer is clean and zeroed?

[brads70]

You sure your micrometer is clean and zeroed?

 yep, I can feel an ever so slight rock in the pin when in the rod.

[72cudamaan]

Yep, rocking motion is toooo loose. You should have to push it through with your thumb.

[brads70]

Yep, rocking motion is toooo loose. You should have to push it through with your thumb.

 

[brads70]

Looking around on Moparts, came up with these posts....
http://board.moparts.org/ubbthreads/showflat.php?Number=5835466

[jimynick]

Why not cut to the chase and invest a call to either Ray Barton or Hughes Engines and ask the simple question- how much? If you do the oven thing, don't forget to throw the pins in too and THEN measure them. 

[brads70]

So I called Muscle Motors and told them my concerns, they said leave it with us and we will call you back. That was at least a week ago with no phone call? Not getting a warm fuzzy feeling here...

I was thinking though.... the pistons can be used as either floating or press on as I understand it. So to my way of thinking the clearances on a floating set up should be pretty tight no? The reason muscle says they need to be at .0008" is so the rod won't seize on the pin,( see there web site) but if that happens ( which I can't see happening as the clearance gets bigger with heat?) then the wrist pin will just spin in the piston like a regular press on style no?  Am I missing something here?

[Chryco Psycho]

the piston clearance to the pin should be the same either way as it floats in the rod & piston , in a floating system . You still have to fix the rod problem though .