Help me out here guys.. Ive got 2 ways i can go. This is a forged 370 that will see alot of n2o and very little street use and will usally be on race gas. I havent decided on a cam yet it will probly be whatever i find at a deal on here. Would you:
1. Stock 317s with a mild bowl job and good valve job milled .030...
2. 5.3 heads with a 2.00 intake valve with the bowl and runners mildly ported.
How far behind the the 317s are the 5.3 heads as far as flow? I think the compresson bump will help if the flow is close. Let me know what you guys would do. thanks...

 

IMO 5.3 will be better lots of members got great results with those heads.

I have 317 with TT Setup works awesome but for N/A and Nitrous I dont know if they work great for the setup.

 

Milled 317s for sure with bigger valves (2.04/05 intake and 1.57 exhaust).
Why? because of the bore and runner design.
5.3L only if fully ported.

 

Do yo have to change the seats out to put a 2.02 or 2.05 in a 317? If you guys think they will do better ill do the valves and a bowl job. How big of a valve can you put in the stock seats on int and exh. Would still like to know more on the 5.3 heads though....

 

2.02/1.57 will fit perfectly with a valve job on stock seats.

While 2.04 would still fit it is counter productive (stock seats 2.02), so IMO 2.04 and bigger should have aftermarket seats.

BTW flow difference between 2.02 & 2.04 is like ~ 5 cfm +/-

5.3L unported are more restrictive than even LS1 castings, 6.0 castings are same as 243 LS6/2 castings but with bigger chambers.
5.3L shine only if fully ported, then you benefit of a small chamber as well.

Since you will have pistons with valve reliefs, you can mill the 317s as you like.

 

What is the most you would mill the heads with a .615 cam? I dont want to cut them too much and have problems keeping headgaskets on it.....It will have ARP bolts or maybe studs and like i sais it will see alot of nitrous.

 

i dont like to remove any more than .030 off ANY LS head.
maybe .040, but then manifold aligment issues may arise.
using gm mls gaskets and arp head bolts or studs.

 

What does lift have to do with milling?

To answer your question I would need more info.

Cam specs at .006 lift
Bore size
stroke size
rod size
gasket thickness compressed
valve relief size
Piston hole position (piston deck height)

 

Milling has alot to do with PTV if it already close. Im going to nail down the cam in the next couple days and then i will have more to work with..

 

PTV has nothing to do with lift at .050 at 99.99% of the durations we use. You must be confused and thinking tappet lift which is a different matter.
Max lift occurs at BDC and not TDC where contact with piston occurs (usualy within 15* BTDC or ATDC