Hello everyone! First time poster here, but have been trolling this site almost everyday hoping to soak up some of your intelligence for a build that I am currently undertaking! First off I have a 1988 GMC Sierra Stepside that was my fathers that I have been sitting on for sometime, and have decided (no brainer) to install an LS motor. Picked up a junkyard 2003 5.3 lm7, should have went with a 6.0l but feel confident enough with the 5.3 here is a few parts I have in mind already:

76mm Turbo .96ar (still deciding where to purchase my turbo from)
Isky Tripple 12 Cam
Dual springs
Scat I Beam rods
ARP Bolts throughout
Sticking with Stock Crank
4l80e (built)
Dont have a stall in mind ATM or gearing... I'm getting there!
Intake is remaining stock, since its FI

This will be a street machine with very little track time, weekend warrior mostly... I would like 500+ rwhp, whatever I need to adjust to get there $$$ isnt the problem (being able to save a little here and there is nice) just want to do it right the first time! I have been reading a lot, but I feel like I am not finding the right answers so...

The reason now for this thread is should I stick with the stock heads (706's) and have them reworked? Go with a different stock LS head say LS6's etc., or bite the bullet and dump money into aftermarket heads? Not looking for a 9sec car or anything just something respectable... Thanks, any insight will be much appreciated would just like your input, and I do not pretend to know a whole lot, but I am learning!

 

I think 317 heads would be a better choice for FI

 

P&p the stock ones 317s will drop ur cr way way down and stall I would get like a 3400 stall

 

Glock's new turbo 5.3 has the stock heads milled .040 lol... Ran 10.51 at 131 so it seems to be working.

 

For 500rwhp, stock heads and that cam with about 9-10 lbs of boost will put you there easy. No need to spend tons of money if that is you HP goal.

 

Yea like Kyle said, Id just run the stock heads and leave them untouched. This is my plan and Im sure Ill see 500 or so with about 12psi.

 

Stock heads got my LM7 into the 11's...

 

Don't go with much bigger valves whatever you do, they might not fit. I had to build a bigger engine to go with the heads I bought lol.

 

So Stock heads are 9.1:1 compression, so if i were to bore the engine say .30 over would it reduce the compression ratio, and in a good way? is there a magic number for compression in regards to forced induction? I figured while I am into the block itself forging the rods why not displace it a lil more... or should I stick to what I have and call it a day? Thoughts....

 

Port, polish the stock ones and put the larger LS1 valves in....that's what I did