Head flow numbers... Finally! (AFR's done by Race Prep)
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Joined: Oct 2002
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Chuck,
I would expect a 7500rpm HP peak and 560 HP w/ all the bolt ons and a rev kit.
I would like something like a 244/254 .656/674 112 2 Deg Advanced.
I figure there is about a 3% average gain in power with just that cam vs the one you mentioned. Not to mention a 500rpm lower HP peak and a 40 lbs ft gain @ 4500. It's peak HP should be within 5 hp of the other one.
Just my thought. It's not a street cam by anymeans but it is a good rag racing cam for your engine.
Good luck,
Bret
I would expect a 7500rpm HP peak and 560 HP w/ all the bolt ons and a rev kit.
I would like something like a 244/254 .656/674 112 2 Deg Advanced.
I figure there is about a 3% average gain in power with just that cam vs the one you mentioned. Not to mention a 500rpm lower HP peak and a 40 lbs ft gain @ 4500. It's peak HP should be within 5 hp of the other one.
Just my thought. It's not a street cam by anymeans but it is a good rag racing cam for your engine.
Good luck,
Bret
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Joined: Jan 2002
Posts: 442
From: Houston, TX
Old threads never die...
They cost about 3700 including parts.
We reflowed the heads at the school and the numbers were down about 20 cfm across the board. That was with a clay radius. Fwiw, the school's flowbench numbers are almost always lower than everybody else's... For example, they'll port a set of LS6 heads that flow like 350-360 on this bench, and locally at other shops they flow 380. And I know everybody has their doubts about GTP's numbers... but just as a comparison, they've flowed lots of GTP heads here, and non of them have hit over 300... including some stage 4 LT4's that were supposed to hit around 330-340. So the fact that they were 20 cfm down from Race Prep's quotes is not anything to go freakin out about... Everyone at the school says the port flow is great for what they are(most were actually amazed they flowed over 300 cfm)... but the low-mid numbers aren't the greatest , and they go turbulent over .650 lift. If we unshroud the valves, and increase the short turn area, these heads would definitely flow some great low-mid lift numbers, and probably pick up another 15 cfm peak.
Case in point, there is at least another easy 50+ hp to unleash from these heads... The guys at Race Prep did a great job, but just were a little conservative. On a smaller cubed motor these things would scream. But since I'm building a stroker I don't want them to be my limiting factor.
Oh, btw, one side note is that I will be dynoing these the way they are before I do any work to them... just out of curiosity to see if Race Prep is right, and see they really do push the numbers they claim them to be pushing... They wanted me to do it this way. So we'll see what happens...
They cost about 3700 including parts.
We reflowed the heads at the school and the numbers were down about 20 cfm across the board. That was with a clay radius. Fwiw, the school's flowbench numbers are almost always lower than everybody else's... For example, they'll port a set of LS6 heads that flow like 350-360 on this bench, and locally at other shops they flow 380. And I know everybody has their doubts about GTP's numbers... but just as a comparison, they've flowed lots of GTP heads here, and non of them have hit over 300... including some stage 4 LT4's that were supposed to hit around 330-340. So the fact that they were 20 cfm down from Race Prep's quotes is not anything to go freakin out about... Everyone at the school says the port flow is great for what they are(most were actually amazed they flowed over 300 cfm)... but the low-mid numbers aren't the greatest , and they go turbulent over .650 lift. If we unshroud the valves, and increase the short turn area, these heads would definitely flow some great low-mid lift numbers, and probably pick up another 15 cfm peak.
Case in point, there is at least another easy 50+ hp to unleash from these heads... The guys at Race Prep did a great job, but just were a little conservative. On a smaller cubed motor these things would scream. But since I'm building a stroker I don't want them to be my limiting factor.
Oh, btw, one side note is that I will be dynoing these the way they are before I do any work to them... just out of curiosity to see if Race Prep is right, and see they really do push the numbers they claim them to be pushing... They wanted me to do it this way. So we'll see what happens...
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by chucks97ss
Everyone at the school says the port flow is great for what they are(most were actually amazed they flowed over 300 cfm)... but the low-mid numbers aren't the greatest , and they go turbulent over .650 lift. If we unshroud the valves, and increase the short turn area, these heads would definitely flow some great low-mid lift numbers, and probably pick up another 15 cfm peak.
Everyone at the school says the port flow is great for what they are(most were actually amazed they flowed over 300 cfm)... but the low-mid numbers aren't the greatest , and they go turbulent over .650 lift. If we unshroud the valves, and increase the short turn area, these heads would definitely flow some great low-mid lift numbers, and probably pick up another 15 cfm peak.
Were these heads cut with a 50* seat? Looks like a compromise was made to get the peak flow. Nothing too uncommon for a race-only head but it does make me wonder.
-Mindgame
Last edited by Mindgame; Apr 3, 2003 at 06:52 PM.
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Thanks Chuck,
It'd be interesting seeing exactly what went into these heads. My gut tells me that there was a bit of compromise made and it might just show in the seat. This just based on what I've seen some porters do to get those big peak numbers over the years.
-Mindgame
It'd be interesting seeing exactly what went into these heads. My gut tells me that there was a bit of compromise made and it might just show in the seat. This just based on what I've seen some porters do to get those big peak numbers over the years.
-Mindgame
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Well a tell-tell sign for me is the seat angle. If they used a 50* seat, which alot of race heads do, then they made the trade-off.... high lift flow was the priority. Look at the area between the valve and the seat with the more typical seat angles.... 30*,45* and 50*. You'll see that for the same lift, the 50* has less flow area, with the 30* having the most.
Guys who are just after torque, like to use the 30* seats, where as say a Pro Stock head or other high-end race head will use the 40-50* seat. Lots of guys are experimenting with the 50* seat right now but according to those in the know, it only works real well on highly downdraft heads. In other words, you really need to raise the port to make them work well at low-mid lift. You need excellent overall port efficiency.
A compromise to low-mid lift flow for sure, but the trade off is worth it depending on what you're trying to do. No general rule as I understand it... it's all about the intent.
-Mindgame
Guys who are just after torque, like to use the 30* seats, where as say a Pro Stock head or other high-end race head will use the 40-50* seat. Lots of guys are experimenting with the 50* seat right now but according to those in the know, it only works real well on highly downdraft heads. In other words, you really need to raise the port to make them work well at low-mid lift. You need excellent overall port efficiency.
A compromise to low-mid lift flow for sure, but the trade off is worth it depending on what you're trying to do. No general rule as I understand it... it's all about the intent.
-Mindgame
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