Guys,

I got a '03 4.8L from CL the other day. If the block is good, I want to swap in a 5.3L crank to build a replacement 5.3L for my DD '04 Silverado with hurt 5.3L. I don't want a stroker motor or anything, just a good truck engine. Budget for this project is 3 grand total.

I need some straight info on what pistons/rods I need to find. This engine has the 4.8L flattops but I haven't pulled them out yet. I want to be able to run 87 octane with a set of 862 heads. Assume a mild cam and mail-order tune. Everything else (MAF, intake, exhaust, etc) stock.

What is the highest compression I can run with 87 octane?
How would you guys put together a 5.3 rotating assy?
Is there a better option than piecing it together from Fleabay?

Tnx!

 

Well, I got the heads pulled off tonight. Castec 706 heads. cracked. That's a bummer, but I've got a good set of 862s. The pistons and cyl walls look OK, I'm guessing 150K miles on this engine. Maybe a bit of surface rust from sitting. Won't really know until I get the bottom end apart.

First step is to choose the CR, cuz that'll limit piston choices. Anybody want to comment on streetable CR with 87 or 89 octane? I'm thinking no more than 10.5:1. That would let me re-use the 4.8 pistons with a 5.3 crank and rods. I drive to work unloaded, but I do tow up to 5900 lbs on the weekends. I would run 87 during the week and 93 octane when towing.

 

I'd probably shoot for about 10:1 CR with low octane.