How many degrees from .004 to .006?
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From: Bethesda, MD
How many degrees from .004 to .006? I've been trying to compare some cams and the specs for some lobes are quoted at .004 while Comp quotes their lobes at .006. Does anyone know how many degrees of duration I need to add to the Comp rating to get an equivalent .004 duration? I'm most interested in the XE-R lobe, but numbers on the XE lobe would be fine.
Time for you guys with a cam doctor to check in.
Time for you guys with a cam doctor to check in.
I may be wrong, but I think they are one and the same. I have been reading David Vizard's book, and he states the standard was set at 0.004" at the tappet. For a small block Chevy with a 1.5 rocker, this is nominally 0.006 at the valve. How does Comp quote their cams, at the tappet or the valve?
.006 and .004 are common lift numbers used to show full duration, since its hard to say exactly when the duration starts, these numbers are the lowest lift to be considered lift duration. the difference would be so small that it wont matter
do they not advertise lift @.050 ?
i was having a lot of trouble wording this lol
do they not advertise lift @.050 ?
i was having a lot of trouble wording this lol
Thread Starter
TECH Senior Member
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From: Bethesda, MD
Originally Posted by camaroextra
.006 and .004 are common lift numbers used to show full duration, since its hard to say exactly when the duration starts, these numbers are the lowest lift to be considered lift duration. the difference would be so small that it wont matter
do they not advertise lift @.050 ?
do they not advertise lift @.050 ?
Yes .05 duration is provided by everyone but advertised duration is helpful for evaluating idle characteristics and determining the point at which the exhaust valve is going to start opening. A small lift can start to bleed off power and I like knowing where that point is.
Joel, I think it depends on the rate of lift of the cam. Like an XE-R cam that travels 49 degrees going from .006 to .050", you would assume that there would only be 2-3 degrees difference between .004 and .006".
But...and this is a big but...when you're lifting only .004", the cam is just barely coming off the backside of the cam lobe and you can travel lots of degrees before you see a lift change. But I digress. I think it's safe to say that for an aggressively ground cam, the difference is only 2-3degrees between .004 and .006" and maybe 3-4 degrees difference with softer lobes.
But...and this is a big but...when you're lifting only .004", the cam is just barely coming off the backside of the cam lobe and you can travel lots of degrees before you see a lift change. But I digress. I think it's safe to say that for an aggressively ground cam, the difference is only 2-3degrees between .004 and .006" and maybe 3-4 degrees difference with softer lobes.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
