Re: fast ramp cams
[Re: can.al]
#803805
09/17/10 05:53 PM
09/17/10 05:53 PM
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Joined: Feb 2004
Posts: 4,501
Gainesville,FL
goldmember
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Quote:
...the comp xe series cams seem to have a bit of valve train noise unless the geometry is perfect...tough to get.
...are other manufacturers' fast ramp cams the same...like Lunati or maybe Hughes?
It's not the fast ramps that make noise,it's the slamming the valve on the seat that causes the racket. I'd avoid the Comp stuff and call Tim @ Bullet racing cams,get a UD hyd lobe(yes .842 stuff) make power and no noise. JMO
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Re: fast ramp cams
[Re: goldmember]
#803806
09/17/10 06:04 PM
09/17/10 06:04 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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technically, the XE lobes are still chevy (.842 lifter) lobes. the XE-HL's are .904" lobes...
and yeah, it's most likely the vast close of the valves, check out the lunati voodoo cams, designed by Harold of Ultradyne. he used asymmetrical lobes, with a fast open, but slower close, and are supposed to be quiet.
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Re: fast ramp cams
[Re: patrick]
#803808
09/17/10 06:22 PM
09/17/10 06:22 PM
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Posts: 4,501
Gainesville,FL
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Quote:
technically, the XE lobes are still chevy (.842 lifter) lobes. the XE-HL's are .904" lobes...(Yep,I guess I assume anyone would know that,so I might have added to someones confusion.)
and yeah, it's most likely the vast close of the valves, check out the lunati voodoo cams, designed by Harold of Ultradyne. he used asymmetrical lobes, with a fast open, but slower close, and are supposed to be quiet.
I have known Harold since the mid 80's and although I love the guy,I don't care much for the VooDoo stuff either. There is often nothing gained buy faster rate of lift(although I know many cannot comprehend that to be fact)The original UD hyd lobes are very nice,make good power and quiet operation.
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Re: fast ramp cams
[Re: goldmember]
#803809
09/17/10 06:27 PM
09/17/10 06:27 PM
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Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
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Quote:
Quote:
technically, the XE lobes are still chevy (.842 lifter) lobes. the XE-HL's are .904" lobes...(Yep,I guess I assume anyone would know that,so I might have added to someones confusion.)
and yeah, it's most likely the vast close of the valves, check out the lunati voodoo cams, designed by Harold of Ultradyne. he used asymmetrical lobes, with a fast open, but slower close, and are supposed to be quiet.
I have known Harold since the mid 80's and although I love the guy,I don't care much for the VooDoo stuff either. There is often nothing gained buy faster rate of lift(although I know many cannot comprehend that to be fact)The original UD hyd lobes are very nice,make good power and quiet operation.
It is not the high rate of lift that makes more HP, it is the extended duration at higher lifts that makes more HP.
My comp XE268 is silent under the hood, I think the problem is the lifters not being adjusted properly or noisy lifters (comp sells most people the Pro magnum lifter that needs lash to do what it is supposed to do).
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Re: fast ramp cams
[Re: goldmember]
#803811
09/17/10 06:54 PM
09/17/10 06:54 PM
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Joined: Nov 2007
Posts: 21,834
Kirkland, Washington
Pacnorthcuda
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Kirkland, Washington
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Quote:
"It is not the high rate of lift that makes more HP, it is the extended duration at higher lifts that makes more HP." Without a fast rate of lift you won't gain area. Well if your correct then adding higher ratio rockers should be a sure way to more HP? Would that make a car faster on the track? How much testing have you done?
The testing has been done ad nauseum. The amount of time (duration) that the valve is open wide, relative to slower rate of lift cams IS the primary power adder in the cam design. Same with roller cams, though they are REALLY able to take advantage of fast lifts.
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Re: fast ramp cams
[Re: Pacnorthcuda]
#803812
09/17/10 07:02 PM
09/17/10 07:02 PM
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Joined: Feb 2004
Posts: 4,501
Gainesville,FL
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Quote:
Quote:
"It is not the high rate of lift that makes more HP, it is the extended duration at higher lifts that makes more HP." Without a fast rate of lift you won't gain area. Well if your correct then adding higher ratio rockers should be a sure way to more HP? Would that make a car faster on the track? How much testing have you done?
The testing has been done ad nauseum. The amount of time (duration) that the valve is open wide, relative to slower rate of lift cams IS the primary power adder in the cam design. Same with roller cams, though they are REALLY able to take advantage of fast lifts.
My hunch is the opening and closing points are the most critical,as well as the opening and closing ramps. I do not follow the greater the high lift area the more power in itself. There are other factors that are never thought of because everyone can find numbers to compare but other factors left out. I guess seeing a cam that seemed similar only smaller with less area and peak lift kill the better looking(at least on paper)cam for power everywhere with the top end being most dramatic got me thinking. Oh well I better leave this one for the experts.
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Re: fast ramp cams
[Re: 64Post]
#803815
09/17/10 08:56 PM
09/17/10 08:56 PM
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Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
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Kalispell Mt.
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I don't consider the com XE series to be fast ramps even though they are faster ramps than mopar cams are. A comp XE HL is a fast ramp, good roller cams have even faster ramps.
Generally a higher ratio will make more power on track or on dyno but a lot of dirrect tests can be missleading by things such as hydraulic lifters colapsing under the added spring preasure cause by multiplying the preasure on the lifter, also if your spring is borderline for the lift and RPM you are already running then a higher ratio can cause valve float and make you run slower but if every thing is still under control the higher ratio will generally make more power unless your cam is just plain too big from the get go, for example you have a .600 lift cam in a bone stock low compression 318 cop 4bbl you will not see an improvement with higher ratio rockers, but if you put some true 1.7 rockers on in place of the factory 1.45 rockers you will feel the differance in power with a stock cam.
NASCAR guys run extremly high ratios 2.0+ and fast ramp speed together because they make good power, especially when you are restricted to very low compression ratios like they are.
The whole cam needs to be desighned together because just like you said opening and closeing points are very important also. The timing events have more effect on drivability, sound, operateing RPM range while lift has more effect on total HP/TQ in those ranges.
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