Am I running wrong CAM for boost?
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From: Dublin, CA
Am I running wrong CAM for boost? This seems to be the best place to ask this question.
I believe it's working too hard to get the boost level, possibly losing boost through the exhaust, and once it does get boost, power seems somewhat low for the boost level (14psi and <550rwtq). It has a D1 blower, 3" Reichard for 14psi while slipping (separate issue). However with a 3.5" pulley the D1 only delivers 10psi to redline. Before that a P1SC needed a 3" Reichard to get to 10psi.
The cam specs are 224/227 .563/.569 114LSA (TR blower cam), and installed straight up (dot-dot). The forged 347 has 8.65:1CR, WCR/A&A stage 2 blower heads, stock exhaust. Plans are to install 1-7/8 longtubes and random cats.
I suspect for my CR I should use a much wider LSA and lower duration, but still have fast ramp and higher lift than stock. Am I running the wrong cam?
The 14psi dyno sheet:
I believe it's working too hard to get the boost level, possibly losing boost through the exhaust, and once it does get boost, power seems somewhat low for the boost level (14psi and <550rwtq). It has a D1 blower, 3" Reichard for 14psi while slipping (separate issue). However with a 3.5" pulley the D1 only delivers 10psi to redline. Before that a P1SC needed a 3" Reichard to get to 10psi.
The cam specs are 224/227 .563/.569 114LSA (TR blower cam), and installed straight up (dot-dot). The forged 347 has 8.65:1CR, WCR/A&A stage 2 blower heads, stock exhaust. Plans are to install 1-7/8 longtubes and random cats.
I suspect for my CR I should use a much wider LSA and lower duration, but still have fast ramp and higher lift than stock. Am I running the wrong cam?
The 14psi dyno sheet:
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From: Foley, Alabama-southern Alabama
I don"t think I would change the cam until you get a good exhaust system including a good set of headers.Blower moters love headers,if you don"t get the old air out you can"t get the new or MORE air in,does that make since??If you have exhaust back pressure(I.E. excessive!!)its killing your combination.The specs on your cam look about right,not sure about the installed angle, if its 114 atdc I think that could be a problem,I would say something like 110 would be better which would be 4 degrees advanced.At 114 atdc the cam is retarded so your intake and exhaust accure later in relation to the crankshaft and pistons.Maybe get your cam degreed and fix your exhaust, then a new tune for sure!!
wider lsa 116, less intake lift 220, + 8 degrees on the exhaust side, and no overlap = happy blown motor and more power across the rpm's. I am not an expert but I read a lot of car magizines.LOL
Thread Starter
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From: Dublin, CA
Thanks for the tips.
I did replace the 3" pulley with a 3.5" to see if it'll hold boost longer, and peak boost is now 12psi at upshift (6,200rpm). It doesn't reach 10psi until about 5,000rpm. The boost peak is moved up the rpm range, and the scenery does go by fast if you keep your foot in it, however it doesn't feel as punchy as with higher boost at lower rpm. I think I'll put the 3" back on.
It doesn't seem right that I'd need a 3.5" pulley to get to 12psi with a D1. I was thinking it was the low CR, but I still suspect the cam.
I don't think the power curves should drop off the way they do, I believe you guys when you say it's the stock exhaust that's to blame.
I did replace the 3" pulley with a 3.5" to see if it'll hold boost longer, and peak boost is now 12psi at upshift (6,200rpm). It doesn't reach 10psi until about 5,000rpm. The boost peak is moved up the rpm range, and the scenery does go by fast if you keep your foot in it, however it doesn't feel as punchy as with higher boost at lower rpm. I think I'll put the 3" back on.
It doesn't seem right that I'd need a 3.5" pulley to get to 12psi with a D1. I was thinking it was the low CR, but I still suspect the cam.
I don't think the power curves should drop off the way they do, I believe you guys when you say it's the stock exhaust that's to blame.
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From: AUSTIN TX
Are you worried about the boost or the power. You can put a set of stock heads on it and that will give you a lot more boost, but less power. The boost pressure is caused by restricting the air movement through the motor. Better headers, and better exhaust will decrease your boost level even more, but will not hurt power (most likely improve it, allthough how much is questionable). I found this out years ago with blown boat motors. We would put a 6-71 on a mostly stock motor and make big boost, then build a serious but equal displacement motor with ported big valve heads and put the same blower back on it and wonder where the boost went. Of course it went even faster though it was making 1/2 the boost. That is when you have to either speed up the blower, or step up to a bigger one. As far as the cam specs, I could see a little larger split but that is about it. Have you run a cranking compression test to see how much cylinder pressure you are making. If it is under 175 or so, you could try advancing the cam, but be aware that this will increase cylinder pressure and the risk of detonation. Also be sure if you go that route to recheck the valve clearance (esp intake).
By the way, I am not an expert either. But I did stay at a Holiday Inn last night.
By the way, I am not an expert either. But I did stay at a Holiday Inn last night.
Last edited by BOWTIE; Jul 6, 2004 at 01:45 AM. Reason: correction
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From: Dublin, CA
I figure both boost and power are too low.
A. (Boost) A D1SC with a 3.5" pulley should make more than 12psi. Also a P1SC with a 3" pulley should make more than 10psi.
B. (Power) A 12psi or 14psi LS1 should be making much more than 550rwhp. Some stock CR LS1/LS6 motors are making well over 600rwhp with over 10psi and P1.
I believe I may have missed something fundamental. I built the motor according to Procharger engine building specs (http://www.procharger.com/bebs.html). Possibly this requires lots of boost (and belt traction) to run 'right'. Again due to CR and heads/cam. I hate to think the only way I can get power (and boost) is with a F1R on top of a 1-7/8" lt header setup. I do have room for boost, on 91octane and 14psi it has 12.5AFR (12AFR on dyno) and 22* timing.
A. (Boost) A D1SC with a 3.5" pulley should make more than 12psi. Also a P1SC with a 3" pulley should make more than 10psi.
B. (Power) A 12psi or 14psi LS1 should be making much more than 550rwhp. Some stock CR LS1/LS6 motors are making well over 600rwhp with over 10psi and P1.
I believe I may have missed something fundamental. I built the motor according to Procharger engine building specs (http://www.procharger.com/bebs.html). Possibly this requires lots of boost (and belt traction) to run 'right'. Again due to CR and heads/cam. I hate to think the only way I can get power (and boost) is with a F1R on top of a 1-7/8" lt header setup. I do have room for boost, on 91octane and 14psi it has 12.5AFR (12AFR on dyno) and 22* timing.
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From: AUSTIN TX
Originally Posted by blu00rdstr
I figure both boost and power are too low.
A. (Boost) A D1SC with a 3.5" pulley should make more than 12psi. Also a P1SC with a 3" pulley should make more than 10psi.
B. (Power) A 12psi or 14psi LS1 should be making much more than 550rwhp. Some stock CR LS1/LS6 motors are making well over 600rwhp with over 10psi and P1.
I believe I may have missed something fundamental. I built the motor according to Procharger engine building specs (http://www.procharger.com/bebs.html). Possibly this requires lots of boost (and belt traction) to run 'right'. Again due to CR and heads/cam. I hate to think the only way I can get power (and boost) is with a F1R on top of a 1-7/8" lt header setup. I do have room for boost, on 91octane and 14psi it has 12.5AFR (12AFR on dyno) and 22* timing.
A. (Boost) A D1SC with a 3.5" pulley should make more than 12psi. Also a P1SC with a 3" pulley should make more than 10psi.
B. (Power) A 12psi or 14psi LS1 should be making much more than 550rwhp. Some stock CR LS1/LS6 motors are making well over 600rwhp with over 10psi and P1.
I believe I may have missed something fundamental. I built the motor according to Procharger engine building specs (http://www.procharger.com/bebs.html). Possibly this requires lots of boost (and belt traction) to run 'right'. Again due to CR and heads/cam. I hate to think the only way I can get power (and boost) is with a F1R on top of a 1-7/8" lt header setup. I do have room for boost, on 91octane and 14psi it has 12.5AFR (12AFR on dyno) and 22* timing.
Staging Lane
Joined: Jun 2002
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From: Palm Beach, FL
[QUOTE=blu00rdstr]This seems to be the best place to ask this question.
I believe it's working too hard to get the boost level, possibly losing boost through the exhaust, and once it does get boost, power seems somewhat low for the boost level (14psi and <550rwtq). QUOTE]
1) Belt slippage, enough said.
2) I know you show head mods, but are you sure your springs are up to the task? I've seen a few situations where the springs just blow open after 12psi if they are not up to the task, serious power loss there. However it usually only shows up on stock or el'cheapo springs.
I believe it's working too hard to get the boost level, possibly losing boost through the exhaust, and once it does get boost, power seems somewhat low for the boost level (14psi and <550rwtq). QUOTE]
1) Belt slippage, enough said.
2) I know you show head mods, but are you sure your springs are up to the task? I've seen a few situations where the springs just blow open after 12psi if they are not up to the task, serious power loss there. However it usually only shows up on stock or el'cheapo springs.
Thread Starter
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From: Dublin, CA
Originally Posted by 10thanvhawk
2) I know you show head mods, but are you sure your springs are up to the task? I've seen a few situations where the springs just blow open after 12psi if they are not up to the task, serious power loss there. However it usually only shows up on stock or el'cheapo springs.
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From: Foley, Alabama-southern Alabama
Is there any way you can check the backpressure on your exhaust system? If you get a better header and exaust you will see a good hp increase.Boost can be misleading,if you build a lot of boost but have a lot of backpressure thats not going to do your power output very much good.If you have less backpressure then more air is going to go thru the engine resulting in more power being made.I think your cam is OK,if I was going to change it I would make the exhaust duration larger in relation to the intake duration say maybe 10 degrees.On another note your CR is OK for a blower motor,if you up your static CR then you"ll have to run less boost, whats the point??Fix your exhaust first!!
Staging Lane
Joined: Jun 2002
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From: Palm Beach, FL
Originally Posted by blu00rdstr
They're West Coast Racing Cylinder Heads from A&A Corvette, CNC machined stage 2 heads for blower application, REV dual springs, REV Stainless valves 2.02 & 1.57, hardened retainers and valve seats.
Now that we know I retract my statement directed at your valves springs.
Fix your exhaust first 
that cam should be fine, i agree your exhaust is probably robbing you 40 hp easy, and at higher boost levels it is the bottleneck in your system. put a 30 dollar cutout in and see how much power you gain, i guarantee it will be a big difference.