I have some old 2379F-40 how far up from the bottom of the skirt do you measure them for piston too wall clearance? Can't find it on search.

Thanks for reply. min spec is .002. I have little more than .003 piston too wall clearance.

Mark that sounds like stock piston clearence? I think we used to set the 2379 closer to .005 or even looser ? Where's George or one of the orhers should have exact spec on those? I know mine were no tighter than 5. I think .003 is tight!

I have the Chiltons book here. 289 hp .003 too .0038 boss 302 .0032 too .0042 351c  .0014 too .0022 boss 429 .003 too .0038. I remember at the mechine shop the spec book said  min .002 and its built into the piston 4.028.  I ran them that tight 10.5 4vcc heads no problems.  Ran them up to .004 start loosing power. Someone else on this forum ran them that tight with no problem. Don't remember who.

There's no 'F' on it so its forged?

I have the same pistons and they dont have the "F" on them either. They do have TRW in the bottom of the piston though. From what I understand is the L2379 was a TRW factory Forged replacement.

I never ran them that tight on the early pistons but it could be? I know the newer forged pistons like to be tighter but I didnt think those were? Even so if you ran them tighter than .003 I would run them! A street motor can stand to be tighter if it was pure. Drag I would loosen up. Remember .002 is minimum I see quite a few on fm site say .004 minimum so I think I would be a little looser than tight! Also those chilton specs are for stock cast pistons not the forged 2379 trw.

Mark I did some digging also and they did call for .002? That seems tight as the new hypers are around there maybe a little snugger! Anyhow 3 shouldn't hurt you at all, I was hoping George would chime in he's likely ran a ton of those pistons. I used 1set and switched to kb hypers.

depends upon the alloy and the diameter of the piston, i figure we're talkin somewhere right around 4" here?

so that leaves the alloy that the pistons are made of. 2 popular alloys for forged pistons, 1 expands quite a lot and the other not so much

http://www.carcraft.com/techarticles/ccrp_0810w_mahle_piston_alloy_comparison/index.html

you need to determine which alloy the pistons are and clearance accordingly, you can't go by what 'some other' pistons spec for clearance. it WILL leave a mark

there'll be phantoms, there'll be fires on the road... and the white man dancing