Cam numbers help
Thread Starter
Teching In
Joined: Aug 2022
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Cam numbers help Hello guys, Doing a boosted LS3 Gen 4, 418 I spoke with a couple guys over the camshaft numbers and I feel like they are a little off.
(used to run only nitrous engines 1st time doing a boosted)
LY6 Block, Callies Crank 4.100 & 6.125 H rods, 4.030 JE pistons -14CC, 1.7 Jessel Rocker Arms & lifters, STOCK HEADS for now.
@50 243/258
Lift .623/6.15
116 LSA install at 112.
Any other recomendations?
thanks in advance.
(used to run only nitrous engines 1st time doing a boosted)
LY6 Block, Callies Crank 4.100 & 6.125 H rods, 4.030 JE pistons -14CC, 1.7 Jessel Rocker Arms & lifters, STOCK HEADS for now.
@50 243/258
Lift .623/6.15
116 LSA install at 112.
Any other recomendations?
thanks in advance.
TECH Enthusiast
Joined: May 2008
Posts: 642
Likes: 572
From: Carnation, WA
That’s almost 20 degrees of overlap. Seems like a lot for a turbo motor if you want to drive it much on the street. But I don’t know anything about turbo LS setups. I may learn something on this thread, depending on who replies. 🙂
Some more information about what you intend to use it for might get you some better suggestions.
Some more information about what you intend to use it for might get you some better suggestions.
Joined: Apr 2006
Posts: 3,890
Likes: 1,137
From: Grand Rapids, Michigan
I mean, I'm just guessing without actual valve events, but that cam seems like it would have a pretty significant amount of overlap to be using it in a boosted application. And knowing where your boost is coming from is important. Turbos like different valve events than blowers, so knowing that would help pinpoint whether or not the cam is appropriate for your build.
Thread Starter
Teching In
Joined: Aug 2022
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Car will have a pair of VS RACING 7875 billet 1.25 T4 , hoping to go 14-20 PSI of boost.
Car will be a 90% track and 10% street.
Car is about 2500 Lbs.
Car should be running either 100 yards and hoping to close aoout 7800RPMs.
Everything on the car is "designed" to be boosted but still almost 20 degrees of overlap for the cam??
Let me know if need more info.
Car will be a 90% track and 10% street.
Car is about 2500 Lbs.
Car should be running either 100 yards and hoping to close aoout 7800RPMs.
Everything on the car is "designed" to be boosted but still almost 20 degrees of overlap for the cam??
Let me know if need more info.
Joined: Apr 2006
Posts: 3,890
Likes: 1,137
From: Grand Rapids, Michigan
As I've said in other threads, the @.050 duration figures do not tell the entire story in regards to how a cam will behave, especially in a turbo application. It's nice for comparing cams and most people have adopted the figures in everyday use, but @.006 valve events still matter. Crack open an intake valve .006 during an overlap period in a turbo combination that has a 2.5:1 pressure differential, and I guarantee there's going to be exhaust reversion into the intake tract. However, given that the OP is planning to have 2 fairly large turbos with 1.25 A/Rs, I doubt there's going to be an issue with a large pressure differential, and the cam specs he listed are most likely going to work well. Me, I'd still like seeing what the @.006 events are, but that's because I'm a stickler for numbers.
TECH Enthusiast
Joined: May 2008
Posts: 642
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From: Carnation, WA
I have so far not had great luck trying to get .006 numbers out of the (few) cam manufacturers that I’ve asked. What I was interested in was the asymmetry of the lobes. The difference in crank degrees between .006” and .050” numbers can’t be assumed to be equal on the opening and closing flanks. The manufacturers I’ve asked have been pretty coy about this information.
I have not asked Cam Motion, I suspect they’d be more forthcoming. I’d like the information in order to better calculate the DCR on any cam I’m considering putting in my pump gas 11.8 CR engine.
I have not asked Cam Motion, I suspect they’d be more forthcoming. I’d like the information in order to better calculate the DCR on any cam I’m considering putting in my pump gas 11.8 CR engine.
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Joined: Apr 2006
Posts: 3,890
Likes: 1,137
From: Grand Rapids, Michigan
Asymmetric lobes definitely make extrapolating valve events even more difficult. Which is why I won't take results as gospel for @.006 or even @.050 valve events when using basic duration/LSA/ICL figures and math to derive them. I've personally did the math on some Comp designs a few years back and my numbers came out entirely different than what was on the cam cards, due to asymmetry. Is it going to make a huge difference for most people? Probably not. However, if there's room for precision, why not be precise?
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Comp cams publishes their duration at .006, .050, and .2 lift for their various lobe styles in their master lobe catalog. Cam Motion told me to add 54* to their duration at .050 to get to duration at .006. Tx Speed was very open during a phone call as to their duration at .006 compared to their duration at .050 which is published for a lot of their cams. I just don't remember their numbers.