Ok so I picked up a 98z last weekend. 10k miles ago it had the motor rebuilt by a local shop (I called them to verify the work, and I have the invoice.) Yesterday while going through the car, I put a magnet on the block and it stuck. I looked at the casting number and it's a 12567393(4.8 or 5.3) My research has indicated a max bore of 99mm on this block, however the piston kit installed was the mahle power pack ls1314030F04 (4.030) and eagle rods, but no part number given for those. And stock crank. Can the smaller truck blocks be bored that large? or is the most likely scenario that they installed a different piston kit but didn't reflect that on the invoice. I'll have the engine out and apart at some point, but I wasn't planning to do that just to see what's inside lol. Any help would be greatly appreciated!

 

And you're sure you were given the right part number for the pistons?

 

All I know is that is the part number on the invoice. I'm guessing they ordered them, tried to install, realized they were way too big, then ordered the correct pistons and did not reflect this on the invoice. If that's the case I have no idea what size motor this is and it's going to eat away at me lol

 

No the 5.3 block can't fit 4.030 bore Pistons.

I've never seen it personally

I punched a 5.3 block out to 3.905 though before..

The 6.0 block is regularly taken to 4.030 to build a 408 stroker with a 4" crank

They most likely put the 4.030 on the paperwork by mistake

 

yea that's what I'm thinking. My coworker used to work at the shop that built it, so he's going to try to find out some more details for me.