dubrado

iTrader: (20)

I have some stock 243 heads I'm gonna throw on, but am thinking about getting some larger valves before I put them in.

Any issues with that? Will it hurt more than help? not matter? eh?

thanks in advance.

GuitsBoy

iTrader: (4)

The heads are stock?

Porting the heads with stock valves will gain more power than a stock head with only larger valves.

IMO, this is the order in which youll gain teh most power:

1. Porting the heads
2. Milling for proper compression
3. Larger valves
4. 5 angle vs. stock 3 angle valve job

Id spend the money on the first two before touching the valves.

dubrado

iTrader: (20)

so larger valves = good w/o any issues on stock heads

I'm gonna be porting them at home a little

GuitsBoy

iTrader: (4)

Yeah, youll have to get the seats cut and possibly even replaced though. Then a valve job. And IMO, porting and milling yield larger gains.

PREDATOR-Z

You can put 2.02/1.57 on stock seats.

2.04 would fit but pointless since seats are 2.02

slammedchevy

iTrader: (13)

If U Look At The Stock Ls6 Valves To The 2.02 It Is A Wast Of Time And Money U Cant Tell The Size By Looking At Them If It Were Me Id Keep The Stock Size Valve

dubrado

iTrader: (20)

do you need a valve job w.the 2.02 and 1.57's?

GuitsBoy

iTrader: (4)

Yes. Anytime you replace the valve it requires the seat to be cut to hang the valve in the right place.

Like predator said, you can reuse the seats for .020 over valves, but theyll still have to be cut.

dubrado

iTrader: (20)

ok, cool....good information

also real quick...what compression am I looking at if I don't mill the 243s?

GuitsBoy

iTrader: (4)

Depending on the gaskets, figure around 10.5:1 for starters.

Bville-Bud

A couple of dumb questions if you don't mind. I have a 99 C5 and would like find some LS6 heads in the next year.

1. What is "proper compression"? I always use 93 octane, but if I'm on a trip and it's not available...

2. Where would you send the heads to to get them CNC'd and milled?

Proud2bSS

iTrader: (2)

If this is staying internally stock (oem cam, etc) then some "cleaned" 243 heads will bring a good overall gain. I would persoanlly wait until you have the 243 heads, as they have a little more compression due to the smaller combustion chambers. The port runners are bigger and better flowing versus your current heads. Unless you are going a much bigger cam, these would more than help.

If you determine in a year that you want to really bump the HP, then you need a preoven matched cam/head combination.