A buddy of mine wanted to know what would be the best set of heads to run on his boosted 5.3L for a daily driver he's gonna run about 12 to 15psi heres what he has so far. He wants to run 317's but hes afraid that the car will be a dogg out of boost will Ls9 gaskets be better as far as compression any info would be greatly appreciated thanks! He's looking for about 600hp

05 5.3L with stronger rods(factory)
317 heads and a set of 706 heads (which one is better)
04 Zo6 cam, LS3 springs good to .570 lift hardened pushrods 7.425
Ls1 intake Manifold and throttle body
Garrett T70
2800 yank ss built trans/411 gears
80lb injectors/Fast fuel rail

 

The 317s are a good head, but may make it a bit sluggish out of boost. Tons of people run them without complaints too though. LS9 gaskets are going to have a negligible change on compression .1 at the most I would think.

This one is just my opinion, but I wouldn't prefer a 4.11 for a turbo build.

 

Yeah he's gonna change the gears out 3.42's once he gets the money but for now he wants to go with what he has for now. Hes really afraid of the car being a dogg out of boost with 317's because the car is his daily driver but it will see some track time.

I told him 706 heads arent that good

 

For the money you will have in switching out to 317s you can have the 706s ported. Plenty of guys have ran them (706s) with no issues. The 317s are going to give up a LOT of compression.

If you are talking about ported and milled 317s that is different, but then you have to make sure to keep an eye on PTV clearances, etc. It won't be a concern with his current cam, but could be in the future.

 

ok cool thanks I'll let him know that he can run the 706's will he have to lower the boost with stock compression?

 

No, he will be fine. A friend of mine has a junkyard 6.0 (older style, worse rods) with around 700whp with no problems.

As long as the tune is good, you will be set.

 

Run what he has,
Use good springs,
Get some different gears.

Porting not really needed unless he wants to.
Remember he is pushing the air in.
Porting won't help a boost engine near as muchas a na engine.

 

Good valves and valve job will be worth a lot more that porting on either head with a turbo motor. Because of that I would go with the better flowing 317s. And have the 317 heads decked while they are at the machine shop to keep compression.

 

Yea just throw the turbo on with some good valve springs and he is set.
Do gears later when he can, or do gears first.


I ran a turbo on a bone stock 5.3 for about 2 years. Then went LQ4 and another year before i did cam and springs.

 

ok thanks guys so should he get rid of them LS3 valve springs and get some aftermarfet springs? What lift should the springs be .600 or higher which lift on the springs should he go with?