EddieK

Just wondering how much (ballpark) HP can i gain by switching to CNC ported 243/799 heads.

Fresh LQ9, 317 heads
1 7/8 headers
3" exhaust
TBSS Intake
LS3 TB
54lb injectors
Cam motion Titan 4 cam
227/232
.612"/.595"
113 Lobe Center Angle with a 109 Intake Centerline

Circle D 245mm 3400 stall

Thanks

Kfxguy

iTrader: (1)

20 housepower

EddieK

That's it?? I thought it would be more like 40-50.

Kfxguy

iTrader: (1)

well then 40-50. (Not likely).

EddieK

I just thought that more compression, more flow, better combustion chamber would equal to little more than 20hp.

SLOW SEDAN

iTrader: (13)

On a turbo setup I gained 3MPH going from 317 to 862’s no other changes.

ddnspider

iTrader: (26)

You're not picking up 40 or 50hp from a head swap on that setup when you're running a stock intake manifold.

low2001gmc

iTrader: (148)

About 15 being head flow is very similar with main thing being going from 71 to 65ccs. With that cam, I would definitely mill and run Cometic 40 gaskets for increased compression. This will make you more power everywhere.

Kfxguy

iTrader: (1)

do and see? Picking up is better than not picking up, right? As long as you are headed in the right direction, dew it.

Kfxguy

iTrader: (1)

I went from stock ls1 heads (don’t remember which ones) to ported 243’s and I felt, meh. I guess it helped. The cam definitely helped more than the heads.

G Atsma

It may be possible the heads needed the bigger cam to realize their full potential.

Kfxguy

iTrader: (1)

I may have worded that wrong. I did the cam first. Made a pretty good difference. I expected more from the heads. Maybe 20hp if I had to guess. I just remember that was a lot of work and money for such little gain. The heads flowed over 300 at .600 on the intake and like 230 on the exhaust. Think it was 226-227cfm. Really good low lift and mid lift numbers. I think at that point, heads weren’t badly needed, although they helped, it just wasn’t worth the effort/cost at the time. Would I do it again? Yea, because I’m a dummy. It all adds up but I don’t think 50rwhp worth like the op is thinking. But hey, I could be wrong. Do it and see!

G Atsma

I generally like the advice given by some to just mainly concentrate on smoothing and blending the bowl areas, plus a good multi-angle grind on both valves and seats. It has been mentioned that just the mentioned steps comprise 80-90% of gains to be had with porting, as those areas are the weakest flow areas in a stock head/valve setup.

SoCalDave

Sell your 317 heads and get a pair of 243 heads. That will bring your compression up which adds torque even in stock form. If you get a ported a set of 243s you'll gain even more.

foxfan

Have your 317 heads decked about.030 and save you a lot of money especially if your staying n/a

gagliano7

That is exactly what he is doing he just wants to know how much hp he will gain.

SoCalDave

If Fontana was open, I would give time slip comparisons. Irwindale should open in 2021 so I'll take my '01 with ported 243 heads there to compare my times. I'll share then.

wannafbody

iTrader: (2)

Ports are the same between 243 and 317, the difference is the smaller chamber on the 243.

SoCalDave

The reason you have your heads ported by someone/CNC is because it addresses the major pinch-points in the head. Usually the throat is a major pinch-point which improves flow and adds significant power. Bigger throat on intake and exhaust and more compression will add quite a bit of power to your 6.0 liter.