stock pistons

[Chris]

Read somewhere that the stock pistons on the 4.0 could be dished out safely to 29-30 cc's and still have .250 left. Don't know if this is true or not, but if it is and someone is not having to bore the cylinders, this could be a fairly cheap way to go. Does anyone know if there is any truth to this? I'm looking at boring out .030, so won't work for me, but maybe someone going with the 4.5L this could be an easy way to help with compression.

[Flash]

Read somewhere that the stock pistons on the 4.0 could be dished out safely to 29-30 cc's and still have .250 left. Don't know if this is true or not, but if it is and someone is not having to bore the cylinders, this could be a fairly cheap way to go. Does anyone know if there is any truth to this? I'm looking at boring out .030, so won't work for me, but maybe someone going with the 4.5L this could be an easy way to help with compression.

I have hered of this being done......But not to 30

[oletshot]

This is my build. Not dished to 30cc's. Stock pistons dished to 23cc's, thinnest spot on the dish is .250" going almost up to .300" thick in spots. Because the inside of the piston is not machined, it isn't flat, so getting an actual thickness is hard. Static compression works out to about 9.0:1 with the .043" head gasket and quench matches stock 4.0L. You could dish a little more, maybe 25-26cc's as the area that was at .250" thick was a small dimpled area in the center of the piston. If you average it out it was probably about .275" thick. I don't see a need to go to 30cc's unless you planned on decking the block to get even better quench. My stroker is assembled except for new rockers (thanks flash for pointing out the need for new rockers when lift is changed, I never would have thought of that), but it will be awhile before I have any results to post. It's a replacement for my son's 2.5L YJ. I donated the drivetrain and paid for the stroker build, but it's his job to buy the required swap parts, which we have zero of.

[gradon]

That's why I'm just now considering the Yella Terra's, since I have to buy new rockers for the higher lift.

[Flash]

It's real funny about that comment, as I too, had never put that together until the middle of that post, it just popped in, out of no were ...........and realize it was a vary good point to put out there.

I have hered time and time again of noisy valve trains,(that developed after a stroker build) and how much quiter they became when they Switch to a aftermarket roller rocker arms.......But, up to that moment, i had just chalked it up to the preload of the lifter being check closer and adj being done when the rolle rocker arms were put one.


Flash