info on n/a engines what cam
03-17-2004, 04:33 PM
#31
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Chrome;
I'd go 10:1 CR and run 92 Octane. Dart single plane with King Demon, IMO you'll need more carb than 1090. Talk with Demon and they will set you up..nailed my TR set-up. Big Inch motors need a lot of carb especially running singles.
The set-up you propose will put you ~750HP give or take and ~750 TQ. I did not run desktop dyno numbers, but that will be very close.
I'd go 10:1 CR and run 92 Octane. Dart single plane with King Demon, IMO you'll need more carb than 1090. Talk with Demon and they will set you up..nailed my TR set-up. Big Inch motors need a lot of carb especially running singles.
The set-up you propose will put you ~750HP give or take and ~750 TQ. I did not run desktop dyno numbers, but that will be very close.
03-17-2004, 05:32 PM
#33
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You don't need King Demons or Dominators. They will make about 10 more hp but you will loose about 30#/ft of torque.
I pulled the dyno numbers on our 540 CID for air usage
3600 506 SCFM
4400 673 SCFM
5000 778 SCFM
572 CID
3800 528 SCFM
4600 720 SCFM
5200 815 SCFM
The 540 was 645HP at 5200 and 680#/ft at 4500
The 572 was 702HP at 5200 and 731#/ft at 4400.
You need a good prepped 850 or a out of the box 950HP carb.
Chris
I pulled the dyno numbers on our 540 CID for air usage
3600 506 SCFM
4400 673 SCFM
5000 778 SCFM
572 CID
3800 528 SCFM
4600 720 SCFM
5200 815 SCFM
The 540 was 645HP at 5200 and 680#/ft at 4500
The 572 was 702HP at 5200 and 731#/ft at 4400.
You need a good prepped 850 or a out of the box 950HP carb.
Chris
03-17-2004, 07:27 PM
#34
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I don't know Chris, I alway thought you sized the carb at ~130% of cfm for best performance depending on intake selection. 130% would give 1011cfm for the 540cid you listed and 1060cfm for the 572 at the listed rpms. 950cfm would be restrictive on the top of the rpm band.
Dave
Dave
03-17-2004, 08:13 PM
#35
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My 632" liked 2X775 Race demons that flowed 980 each.
900HP@6300; 820 Ft/# @5000
Agree with Blue Thunder, a 950 and esp. 850 is choking a 572, even more so if you turn it 5500 or above. A Lot has to do with how your heads flow and how well matched the cam is as to how efficient the motor is. More efficiency = more carb, especially as rpms rise.
Talk with Demons tech department, give them your exact set-up and see what they recommend, they are pretty good. Only thing I had to do to my TR set-up was add 2 jet sizes all the way around, perfect otherwise.
900HP@6300; 820 Ft/# @5000
Agree with Blue Thunder, a 950 and esp. 850 is choking a 572, even more so if you turn it 5500 or above. A Lot has to do with how your heads flow and how well matched the cam is as to how efficient the motor is. More efficiency = more carb, especially as rpms rise.
Talk with Demons tech department, give them your exact set-up and see what they recommend, they are pretty good. Only thing I had to do to my TR set-up was add 2 jet sizes all the way around, perfect otherwise.
Last edited by jdnca1; 03-17-2004 at 08:21 PM.
03-18-2004, 06:19 AM
#36
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I agree there are a lot of factors in carb size
I know the basic rule of thumb is
carb cfm = VE*(cu. in. * max rpm)/ 3456
Now that said, dynos most of the time show an engine likes more carb or less carb, etc than this basic rule. So, VE is how efficiently your heads flow... how does this relate carb cfm and to posted flow numbers of the head manufacturers? If we assume 100% VE (Factor of 1), on a 540 turning 5500 rpm, then carb cfm = 860cfm.
Now we add a more efficient set of heads that raise the VE to 105%, that still does not account for the huge carb size some of these engines seem to like?????
So again, how does the posted flow numbers of manufacturers relate to carb cfm?
Thanks
Zack
carb cfm = VE*(cu. in. * max rpm)/ 3456
Now that said, dynos most of the time show an engine likes more carb or less carb, etc than this basic rule. So, VE is how efficiently your heads flow... how does this relate carb cfm and to posted flow numbers of the head manufacturers? If we assume 100% VE (Factor of 1), on a 540 turning 5500 rpm, then carb cfm = 860cfm.
Now we add a more efficient set of heads that raise the VE to 105%, that still does not account for the huge carb size some of these engines seem to like?????
So again, how does the posted flow numbers of manufacturers relate to carb cfm?
Thanks
Zack
03-18-2004, 06:26 AM
#37
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case in point, jdnca 1's 632"
This is what I'm getting at... obviously jdnca 1's 632" is a great running engine...100% VE at 6300 rpm shows a cfm of 1152 cfm. However he was best running carbs of 1550cfm. That's 134% VE!?!?!?!?!?!?
I don't know of any head that will flow that efficiently without a blower/ turbo....so what is the explaination???
Zack
I don't know of any head that will flow that efficiently without a blower/ turbo....so what is the explaination???
Zack
03-18-2004, 08:33 AM
#38
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When testing these combos, we through alot of products at them. Budget on this was unlimited so we ordered it to try it. Engines were targeted to sport boats with single and twin bravo drives.
Yes the big carbs made more HP on both engines, but we lost torque. The torque plateau is what turns that drive, not HP. Both of these motors had real good VE numbers, the 540's were 101.5% at 5000 rpm and the 572 was 98.5% at 5K. We were shoot for reliable power at the 48 to 5400 rpm range. We got it. I have the dyno sheets in front of me, I don't mind faxing them to anyone so they can see it's not BS.
SCFM is what the engine is actually using at that rpm, not a theoretical calculation, so to use some of the info here if the 540 is using 778 cfm at 5K and I have a 950HP Holley on it that really flows about 990, then I have 127%.
The canfield is an excellent flowing head, small runner, very very good velocity, and an excellent exhaust port. Should have it was designed by HVH. It makes effiecent use of the air it takes in.
Pro Stock stuff will get into the 118% to 120% VE range and the cup cars are a tad higher. That is reliable info because those are our customers.
Last but not least, the cams in these motors were both small.
Chris
Stef's Performance
Yes the big carbs made more HP on both engines, but we lost torque. The torque plateau is what turns that drive, not HP. Both of these motors had real good VE numbers, the 540's were 101.5% at 5000 rpm and the 572 was 98.5% at 5K. We were shoot for reliable power at the 48 to 5400 rpm range. We got it. I have the dyno sheets in front of me, I don't mind faxing them to anyone so they can see it's not BS.
SCFM is what the engine is actually using at that rpm, not a theoretical calculation, so to use some of the info here if the 540 is using 778 cfm at 5K and I have a 950HP Holley on it that really flows about 990, then I have 127%.
The canfield is an excellent flowing head, small runner, very very good velocity, and an excellent exhaust port. Should have it was designed by HVH. It makes effiecent use of the air it takes in.
Pro Stock stuff will get into the 118% to 120% VE range and the cup cars are a tad higher. That is reliable info because those are our customers.
Last but not least, the cams in these motors were both small.
Chris
Stef's Performance
03-18-2004, 09:11 AM
#39
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Chris
Not trying to be argumentative here, but I do have a question for you that I'd like your theorys on. Why is it that A Tunnel Ram always makes more TQ and HP than a single plane single quad? Obviously the long runners and straight shot keeps lots of air and fuel suspended, but carburation is always on the big side of where it should be from a theoretical standpoint. (Mine is 1960CFM) Even 2 X 600's on a 502 this would be true and no one would put a 1250 dominator on a 502 if they expected it to run. So again, interested in your thoughts on why this is true.
Not trying to be argumentative here, but I do have a question for you that I'd like your theorys on. Why is it that A Tunnel Ram always makes more TQ and HP than a single plane single quad? Obviously the long runners and straight shot keeps lots of air and fuel suspended, but carburation is always on the big side of where it should be from a theoretical standpoint. (Mine is 1960CFM) Even 2 X 600's on a 502 this would be true and no one would put a 1250 dominator on a 502 if they expected it to run. So again, interested in your thoughts on why this is true.
03-18-2004, 09:40 AM
#40
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Signal strength and . . .what am I looking for word wise. . .ahhh. . .more consistant air path. On a single your carb signal has to changes more frequent, 4 venturies feeding 8 cylinders. Air has to slow as valves close and open. . .has to change direction. What a dual carb intake, TR or Fabricted does is locate the venturies over the runners, more consistant signal, does not need time to change paths.
Does this make sense to you? I sometimes can't type what is in the head. People say I type in code.!!!!
No offense at all, I've been wrong, I've been right, and I am still learning. But one thing to remember. Torque is measured, HP is calculated. Torque is what moves that drive to spin that prop. People talk about "asking the right questions", next time ask the engine builder not what HP the engine makes, but what is the torque peak and how broad is it.
Chris
Stef's Performance
Does this make sense to you? I sometimes can't type what is in the head. People say I type in code.!!!!
No offense at all, I've been wrong, I've been right, and I am still learning. But one thing to remember. Torque is measured, HP is calculated. Torque is what moves that drive to spin that prop. People talk about "asking the right questions", next time ask the engine builder not what HP the engine makes, but what is the torque peak and how broad is it.
Chris
Stef's Performance
