Cam vs twins
09-28-2006, 01:24 PM
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Doug Smith
09-28-2006, 02:09 PM
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Just for clarity, springs bind at LIFT, not duration. Duration is how long that valve is held off the seat (iow, how long spring pressure is higher than seat pressure). lift is how FAR the valve is opened, and represents (or should) PEAK spring pressure.
The earlier poster is correct that I honestly believe that a Cam is some of the best money to spend on these trucks. The oem cam is anemic, plain and simple. How does Cummins get a cam to last 500k+ miles? Answer: mild specs, slow rate of lift and not much lift period.
The fact that you can build 35+psi of boost with <400hp really says a lot about how restrictive the stock head flow is.
Always remember that the ideal situation is ZERO boost-- that the engine would be able to take in the air as fast as the turbo can supply it. This would eliminate the need for a charge air cooler, and power would be unreal, as engine efficiency would soar (greatly lowered backpressure!).
But we live in a world constrained by physical laws. Our engines cannot consume air as fast as the turbo can supply it. The only way this can happen is if the turbo is incredibly undersized for an application.
When you increase the lift and duration of the cam, you increase both the window the air must flow through (the valve "curtain area") and the time available for it to flow. Both can increase engine breathing substantially.
From a certain point of view, a cam's degree of improvement can be measure by how much reduction in boost you see, all else being equal. The intake will be flow more freely, lowering the restriction the turbo's compressor must "push" against, and lowering the amount of boost pressure at the same airflow (in lb/min).
On the exhaust side, you have some give and take. On one hand, the more complete burn should reduce available drive energy by lowering EGT (because we have a leaner fuel ratio with the enhanced breathing). On the other hand, the cam may INCREASE the available drive energy by letting the exhaust flow more freely out of the valve and into the manifold, extracting more exhaust from the cylinder.
Using a superior grade of alloy steel (in lieu of the factory's use of ductile or chilled iron) for the camshaft allows a much more aggressive profile to be used with no loss of cam durability.
That's why I consider a camshaft to be one of very few win-win upgrades where the only downside is cost.
Yes, the installation is daunting, and I sure as heck won't being DIYing this type of thing, but one installed, you can forget it forever and enjoy the benefits.
ANY AND EVERY CAM should be installed with new springs-- whether it's a performance cam or not. Performance cams get performance springs, stock cams get stock springs-- it's just that simple.
JMO
09-28-2006, 05:48 PM
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How much will a helix 2 reduce EGT's? I noticed when I installed a 4" exhaust, the EGT's were reduced by about 200 across the board. Can I expect a H2 to drop the EGT's another 200 or?
I have a 200HP comp that when set on kill will peg the pyro in couple seconds. The 4" helped a little so I can stay on it longer. If a cam will let me stay in for say 5 seconds longer that's worth it to me. Plus the mechanical lift pump is a really nice added bonus.
I have a 200HP comp that when set on kill will peg the pyro in couple seconds. The 4" helped a little so I can stay on it longer. If a cam will let me stay in for say 5 seconds longer that's worth it to me. Plus the mechanical lift pump is a really nice added bonus.
I notice we are both located in the thin air of the Rockies. Have you run your truck near sea-level and seen the difference in egts under full power? Just back from there, and it is amazing how much cooler things stay and how much less smoke. Anyone got any answers or ideas how us guys living in the upper atmosphere can drop our temps without going to extreme measures?
09-28-2006, 07:36 PM
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Edit: Looks like Don beat me to the punch. I should have read the whole post before answering....
09-28-2006, 07:44 PM
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Find a shop with right tool to do your Oring job. Don't let somebody put that thing in a bridgeport - they'll ruin your head!! Cam + Springs = awesome combination. The best combo, I'm kinda partial, is the F1 Diesel Helix 2 and the springs. While you're at the cam - do the springs. While you're at the springs - do the cam. They work best together.
09-28-2006, 11:00 PM
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I *was* thinking that a cam upgrade would be cheaper than a turbo upgrade for some folks, but once you throw in springs and the other goodies this option isn't going to be as cost effective. Good thread guys- lots of good input 
09-28-2006, 11:14 PM
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I meant lift, dont know why I typed duration. Thanks for the catch!
09-28-2006, 11:16 PM
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Got some money saved up and am wantin to do a few things to my truck this winter. Ive already got valve springs, but i would like to go ahead and stud and oring my head, with either a marine or copper head gasket, and throw a new cam in there. Thinkin maybe a helix 2. Im also gonna be going with a bigger charger. I plan on sled pullin quite a bit with this truck. Would the helix 2 be good for me or would a pullin cam from haisley or scheid be better for me?
09-28-2006, 11:21 PM
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09-29-2006, 01:16 AM
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Maybe I should start a new thread, but hows the drivabilty of a big single with a cam? Will the cam actually help the turbo spool at a lower rpm due to increased flow? Better spool can mean several things to me.
09-29-2006, 02:53 AM
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Not exactly apples to apples comparison, but I did have the Helix 2 in with the stock charger on this truck. Spooled the charger and built boost in my driveway sitting with the tranny in park. I can even get some boost built with the twins in the same condition. It really moves the air.
All else consistent, my "scientific experiments" say that this cam will spool a given charger quicker and moves air more efficiently than the stocker did.
In terms of the springs: do it when you put the cam in, or do it later when you want or have to tear into the top half again....
In terms of EGT reduction: the cam with the modified Ohio style technicooler (
) dropped temps ~100* F. This with the stock charger, roughly equivalent ambient air conditions, same road and driving style.
All else consistent, my "scientific experiments" say that this cam will spool a given charger quicker and moves air more efficiently than the stocker did.
In terms of the springs: do it when you put the cam in, or do it later when you want or have to tear into the top half again....
In terms of EGT reduction: the cam with the modified Ohio style technicooler (
) dropped temps ~100* F. This with the stock charger, roughly equivalent ambient air conditions, same road and driving style.
09-29-2006, 07:34 AM
#45
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Just for clarity, springs bind at LIFT, not duration. Duration is how long that valve is held off the seat (iow, how long spring pressure is higher than seat pressure). lift is how FAR the valve is opened, and represents (or should) PEAK spring pressure.
The earlier poster is correct that I honestly believe that a Cam is some of the best money to spend on these trucks. The oem cam is anemic, plain and simple. How does Cummins get a cam to last 500k+ miles? Answer: mild specs, slow rate of lift and not much lift period.
The fact that you can build 35+psi of boost with <400hp really says a lot about how restrictive the stock head flow is.
Always remember that the ideal situation is ZERO boost-- that the engine would be able to take in the air as fast as the turbo can supply it. This would eliminate the need for a charge air cooler, and power would be unreal, as engine efficiency would soar (greatly lowered backpressure!).
But we live in a world constrained by physical laws. Our engines cannot consume air as fast as the turbo can supply it. The only way this can happen is if the turbo is incredibly undersized for an application.
When you increase the lift and duration of the cam, you increase both the window the air must flow through (the valve "curtain area") and the time available for it to flow. Both can increase engine breathing substantially.
From a certain point of view, a cam's degree of improvement can be measure by how much reduction in boost you see, all else being equal. The intake will be flow more freely, lowering the restriction the turbo's compressor must "push" against, and lowering the amount of boost pressure at the same airflow (in lb/min).
On the exhaust side, you have some give and take. On one hand, the more complete burn should reduce available drive energy by lowering EGT (because we have a leaner fuel ratio with the enhanced breathing). On the other hand, the cam may INCREASE the available drive energy by letting the exhaust flow more freely out of the valve and into the manifold, extracting more exhaust from the cylinder.
Using a superior grade of alloy steel (in lieu of the factory's use of ductile or chilled iron) for the camshaft allows a much more aggressive profile to be used with no loss of cam durability.
That's why I consider a camshaft to be one of very few win-win upgrades where the only downside is cost.
Yes, the installation is daunting, and I sure as heck won't being DIYing this type of thing, but one installed, you can forget it forever and enjoy the benefits.
ANY AND EVERY CAM should be installed with new springs-- whether it's a performance cam or not. Performance cams get performance springs, stock cams get stock springs-- it's just that simple.
JMO
The earlier poster is correct that I honestly believe that a Cam is some of the best money to spend on these trucks. The oem cam is anemic, plain and simple. How does Cummins get a cam to last 500k+ miles? Answer: mild specs, slow rate of lift and not much lift period.
The fact that you can build 35+psi of boost with <400hp really says a lot about how restrictive the stock head flow is.
Always remember that the ideal situation is ZERO boost-- that the engine would be able to take in the air as fast as the turbo can supply it. This would eliminate the need for a charge air cooler, and power would be unreal, as engine efficiency would soar (greatly lowered backpressure!).
But we live in a world constrained by physical laws. Our engines cannot consume air as fast as the turbo can supply it. The only way this can happen is if the turbo is incredibly undersized for an application.
When you increase the lift and duration of the cam, you increase both the window the air must flow through (the valve "curtain area") and the time available for it to flow. Both can increase engine breathing substantially.
From a certain point of view, a cam's degree of improvement can be measure by how much reduction in boost you see, all else being equal. The intake will be flow more freely, lowering the restriction the turbo's compressor must "push" against, and lowering the amount of boost pressure at the same airflow (in lb/min).
On the exhaust side, you have some give and take. On one hand, the more complete burn should reduce available drive energy by lowering EGT (because we have a leaner fuel ratio with the enhanced breathing). On the other hand, the cam may INCREASE the available drive energy by letting the exhaust flow more freely out of the valve and into the manifold, extracting more exhaust from the cylinder.
Using a superior grade of alloy steel (in lieu of the factory's use of ductile or chilled iron) for the camshaft allows a much more aggressive profile to be used with no loss of cam durability.
That's why I consider a camshaft to be one of very few win-win upgrades where the only downside is cost.
Yes, the installation is daunting, and I sure as heck won't being DIYing this type of thing, but one installed, you can forget it forever and enjoy the benefits.
ANY AND EVERY CAM should be installed with new springs-- whether it's a performance cam or not. Performance cams get performance springs, stock cams get stock springs-- it's just that simple.
JMO