Rodding out the details

[GoMopar440]

They'll need to measure ALL the bores top to bottom to find the largest measurement. The largest measurement will dictate what size piston you'll need.

[Dezertxj88]

Just to throw it out there, but theres been many cases of the stock 4.0 pistons breaking off at the side skirts

Yeah and in each instance it's been '96+ pistons that have broken at the skirt, probably because they were rocking too much inside the cylinders.

That I didn't know, again Dino great info. Is it because the 96+ got "better" pistons..lighter and coated skirts from what I've read/have been told.

[neonhomer]

We measured out the bore. 3.888" (Using a bore gauge, and then a dial caliper to measure the gauge)

We measured the matching piston at 3.863 (Using the dial caliper at multiple points on the skirt)... so that gives us a clearance of 0.015"

The FSM say 0.0013 to 0.0015..... This is beginning to sound like a recipe for disaster...

[neonhomer]

My pistons have some of the coating "rubbed" off...

And, the 0.015 was a total clearance number.... the actual clearance between the skirt and cylinder would be 0.0075... Still excessive...