Pulled the heads off my 5.3L last night, sending them off to get cleaned and to have the valve spring kit installed. I started thinking about tearing the whole motor down to freshen it up before I put it in my car. All that is required to make a 5.3L a LS1 is a piston change correct? I may take the block and have it bored and toss on some flat top LS1 slugs, since it won't cost me much money. If I go that route then I'll buy a set of 243 heads and buy a MS3 cam, which is what I wanted to do anyway.

I'd say it would be a good jump in power over the low compression 5.3L bottom end. Have any of you done this?

Don't forget to bore it to 3.9", otherwise your new pistons won't fit.

Absolutely! I was kinda shocked when I saw how small the stock pistons were. I actually had a stock size set of SBC 350 pistons so I compared them. The 5.3L bore looks smaller than a 305... crazy. Which is why I decided to go ahead and freshen up the bottom end. Won't cost much to do, just labor on the bore, polish the crank and balance the rotating assembly.

Out of curiosity, anyone know the max these 5.3's can be bored?

slightly above the 3.9 bore is what I've been told. 3.905, 3.910, maybe a touch higher if you get it sonic checked.

its more economical to find a aluminum 5.7 ls1 block and built it instead.
you are looking at a good amount to bore/hone from 3.78-3.9 at any machine shop.
need to balance crank for new piston weight as well. on top of any other machine work needed. if ur looking for the ci, just forget about the 5.7 altogether and go for a 6.0 build.
none will be cheap. but the prices similar. might as well go for the 6.0 and 4.00 bore.

although, thrre is replacement 5.3 that go up to .060 overbore. speed pro brand and designed for rebuild purpose. less than 500$ for set with rings.

Machine shop won't do the work, they said its too much material to take off and would take too long to do it. So instead of going that route... I'm gonna build a single front mount turbo setup and keep the 5.3L internals. I am going to install ARP rod bolts and studs for the heads. Figured I could break 400 RWHP fairly easy with a turbo install. So here it goes...

Wise. Pricey to do right, but wise

Ya think?

Nope... don't think, I know. lol