Stg 3 5.7ltr GTP heads(2.055/1.60 valves) I decided to have them flowed. Here's the actual #'s that I saw with my own two eyes.

.200 134
.300 203
.400 252
.500 290
.550 306

Are these good or what?
Guys post up some of your stage 2 numbers and let me have a look. Seems like I have the same flow #'s as stage 2 heads. Any comments?

 

Who cares what they flow. Different benches will flow different numbers, and you didn't even list the .600 and plus lift numbers.

 

hmm above the around the .600 lift mark they started to decrease in CFM. So what does that mean? Would someone shed some light on this for me?

Thanks <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Also, do you care what your heads flow? If so, I'll sell you some heads that flow great <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

#s look in line with the CNC LS6 heads that SDPC is selling (LPE). It is true though, unless the comparison is done on the sam flow bench it is not so accurate

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Q:
<strong> hmm above the around the .600 lift mark they started to decrease in CFM. So what does that mean? Would someone shed some light on this for me?

Thanks <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Also, do you care what your heads flow? If so, I'll sell you some heads that flow great <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">All depends on the lift of your cam, if you want the air flow to take advantage of high lift then I'd say yes, you want the flow #'s to keep going up. No?

Jim

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Q:
<strong> hmm above the around the .600 lift mark they started to decrease in CFM. So what does that mean? Would someone shed some light on this for me?

Thanks <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Also, do you care what your heads flow? If so, I'll sell you some heads that flow great <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The decrease in flow at high lift means you have flow stall. The flow characteristics have changed from laminar to turbulent, this is indicative of an LS1 type head as the smoother short turn radius on an LS6 head doesnt suffer from that.

I really don't care too much what my heads flow at high lifts, my mid and low lift numbers kick *** and thats what showed up on the dyno and the track.

 

Fenris,

Care to share your flow numbers? I'd like to compare mine with yours. Also include your valve size and head porter.

Thanks <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Won't matter what the port does above the lift your cam is. It won't get there. Since you were there you could hear the air on the bench start sounding violent. Simply put, imagine your cam never puts the valve in that lift area so it doesn't matter. Don't worry. And those numbers look great. On par with what they advertise. You'll make well over 425RWHP with the right parts.

 

Fenris,
What does your car run BTW?
Chris

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Chris ARE 360:
<strong> Fenris,
What does your car run BTW?
Chris </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That's a good question. Also, what cam are you running? What Lift?

 

ARE 5.3L stage 2 with 2.055 1.60

.100, 79.2, 70.6
.200, 155.2, 123.0
.300, 211.3, 169.1
.400, 253.3, 204.8
.500, 285.5, 225.9
.600, 309.6, 236.4
.625, 312.4, 238.8
.650, 295.2, 239.6

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Q:
<strong> Stg 3 5.7ltr GTP heads(2.055/1.60 valves) I decided to have them flowed. Here's the actual #'s that I saw with my own two eyes.

.200 134
.300 203
.400 252
.500 290
.550 306

Are these good or what?
Guys post up some of your stage 2 numbers and let me have a look. Seems like I have the same flow #'s as stage 2 heads. Any comments? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The point of stall or turbulence on any lS1 based engine will actually be higher when running on motor in car because testing on bench without intake on head is a flow figure that wont be seen in real life run conditions. When flow thru port is reduced from intake manifold losses, point of stall or turb. goes up to much higher lift. My take is less flow activity makes port and short side shape less critical in respect to lift range.
I would want to know port volume of each head being compared, and where extra volume was ground in port to determine which heads would perform best.

 

Thanks for the helpful replies guys. It is now much clearer.

 

Absolute Speed stage 2 (2.02/1.55)
</font>

• <font size="2" face="Verdana, Helvetica, sans-serif">.200--159</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.300--212</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.400--272</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.450--288</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.500--297</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.550--299</font></li>
• <font size="2" face="Verdana, Helvetica, sans-serif">.600--307</font></li>

<font size="2" face="Verdana, Helvetica, sans-serif"> The port volume is aprox. 210cc.The 600 number is way out of most cams lift range.Keep in mind motors do not see the true lift of a cam lobe transfered to match the valves actual lift.There is lift loss in the components (lifter,and components flex) .30 thousandths in most cases I have been told.This is the big benefit of a solid roller you get just about what the cam spec is in actual lift.So a .580 cam may actually only see 550 lift under race conditions.

 

You are talking about valvetrain deflection, and it shouldnt be as high as .030". If it is you dont have true 1.7 ratio or your choice of pushrods is too flimsy. You should measure your intake port volume because 210cc is very small for the flow numbers you have. I think you will find its larger than that. I have measured stock port as large as 206cc.

 

Actually, from what Jay has told me (and previously posted) his Stage 2 heads are only 209 cc. This is one reason I think his heads are so successful --- great flow #'s w/ small port volume = high velocity.

 

That figure of 30 thous was given by a top engine builder here on the east coast.Perhaps this figure is true of older design small block Chevys and the LS1 thru it's newer design and components does not suffer as much loss?There would have to be a measureable amount of loss at W.O.T./high rpm's what are your findings?The volume is what Absolute gives with their port design.I agree the flow numbers are great for the given volume when compared with many other given specs.I will double check that with Jay.I do remember 204 was given as an "average" port volume stock.

 

LS1derfull I quizzed Jay on the port volume issue.I stopped by his shop and while I was there he cc'd a stage 2 intake port for me.I was off a bit with the 210 figure it is indeed 209cc's.If by chance you read my above post I am still curious about the deflection numbers.I'd like to have your take on it.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JFM-jr:
<strong> LS1derfull I quizzed Jay on the port volume issue.I stopped by his shop and while I was there he cc'd a stage 2 intake port for me.I was off a bit with the 210 figure it is indeed 209cc's.If by chance you read my above post I am still curious about the deflection numbers.I'd like to have your take on it. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Wow that is a very productive port design. Is lump in port roof where rocker arm bolt boss is left intact? Deflection is more dramatic with solid rollers because of extra valve spring tension used to control radical cam lobes. The valve lift loss that you or i are likely to have is going to be from hydraulic roller lifter deflaTION. Running correct viscosity oil will help with this kind of lift loss. Tighter tolerance aftermarket lifters with controlled bleed rates would make more power with extreme design Hydr. lobes. Sometimes actual variances with lobes ground on cam are responsible for lost lift at valves. Thats why cam doctors are great to have. I havent checked deflection on my current set up, but i will at some point. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

My Absolute Speed Stage II Heads were:

5.7l '98 LS1 Heads
209cc int runners
milled for 10.8:1 comp
valves: Manley Pro Flow 2.02/1.578
Exhaust #'s are without a flow tube

Lift Intake Exhaust
200 159 107
300 212 146
400 267 193
450 284 203
500 296 217
550 301 220
600 307 223

John.