absolute

There has been lots of talk about port volumes and volocity theory on the board. Im going to explain how Ive come to the volumes I have now. The origanal prototype port measured 220 cc's with a 2.02 valve. after the port was programed to cnc to clean up the entire port, it grew to 224 cc's. All heads up untill recently had a flat faced 2.055 valve. The combonation of the flat face, 2.055 diameter and putting the larger valve sitting as high as possible on the seat increased volumes to the 231cc's. With the larger 2.055 valve alot of extra volume can be missleading. If you took a lpe 255cc ls6 head {255 cc's with a stock 2.0 valve} and installed the flat faced 2.055 valve on the highest point of the seat you will find volumes in the 260's.
All stg2 heads now come with a 2.02 valve and 225 cc runner volume that flows 313-315 cfm, both heads with the 2.055 and 2.02 are making the most power you could find if you look at the dyno section.

With modern porting you will see that volocity can increase in the right places of the port. To make it as simple as possible to under stand picture a veturi. large at both ends and narrow in the middle. if you pictur a port in the head the same thing can be done. opening up the entry to the runner a certain percentage of valve diam. keeping the cross sectional area narrow then opening the bowl area the same percentage as the runner, volocity will increase before the valve head. this is how I get the high flow numbers through the intake That I produce.

I have found through my years of hand porting the port that works the best with this engine, with the shops like lg motorsports, thunder racing and vette doctors I have seen what works with set ups that are identicle, the only change being the port designs. I now have a ls1 cnc port that has produced up to 55 hp with a broad flat torque curve with just a head swap

Patrick G

iTrader: (14)

Good info. Well said.

9T9BlueTA

iTrader: (2)

Interesting. I cant wait to see how your heads perform on my car with TTP's cam Jay.

Brian2001SS

iTrader: (1)

If I understand you Jay, these are your stg 2.5 your speaking of? What or how does the 2.04 valve benefit your stg. 2 heads instead of a 2.02?

Camaro ChriSS

Sounds good. I look forward to getting my heads which are on order.

02RedHawk

iTrader: (17)

Thumbs up to Jay!

Can't wait to get back my Stage-II LS6 heads!

jermstyle

I'm counting the days until my S2.5 5.3 heads come in... Jay knows what he's talking about.

Camaro ChriSS

I'm curious about that too.

Is it the S2 heads that are 2.02 an dthe 2.5 heads that are 2.04 or 2.055?

KGSloan

i've got 2.04's in my stage 2 cnced heads, FYI.

Camaro ChriSS

I just talked to Jay and I think he has cleared things up for me on the 5.3 heads. All new ones are going to be 2.02/1.575 (not 2.04 or 2.055) with the 225 cc runner. He says the past heads were a 2.055 valve intake size, and he is scaling the size down.

Sounds good for a 224 XER cam.

94form2000z

iTrader: (10)

Wow going back to the smaller valves. So if you just so happen to pop back into the thread Jay can you tell me what size valves I have again? I got mine before you started using the bigger valves in the 5.3l heads.