cam specs......i think i'm disappointed

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green67cuda

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well, i took the valve cover off and connected my dial indicator, hoping to confirm what I was told when i bought the car....that it has a .509 lift cam

much to my disappointment, i found that it has .400 lift at the valve.....and although i know it's supposed to be tappet duration@.050, i measured it at .050 VALVE lift....got *about* 216.....i know the cam duration will be slightly lower......BUMMER

the thing i don't understand is that it has a nice lope to it. seems odd to me
so what i have deduced from this is that someone seems to have taken a stock 72 400, added 452 heads, a torker 383 intake, windage tray, Mallory ignition and dizzy, Mopar aluminum valve covers, a new holley, and some other stuff.......

or MAYBE i'm doing something wrong...i measured it at the top of the valve retainer....

anyhow....gotta figure out my CR somehow so i don't go too overboard with a cam
 
I was told when i bought the car....that it has a .509 lift cam

much to my disappointment, i found that it has .400 lift at the valve.....

Looking on the Mopar perfromance parts page, I don't see any B/RB Purple cams listed with less than .430 lift. The stock cam as listed in the Mopar engine book is .410 lift. Something just doesn't seem right about your measurement. :scratch: You may want to take the rocker arm out of the equation and just measure the cam lobe directly off one of the lifters. And measure 3 or 4 different lobes to check for wear.
 
I could be wrong here but if you are measuring the valve don't you need to multiply that number by your rocker arm ratio?
 
I could be wrong here but if you are measuring the valve don't you need to multiply that number by your rocker arm ratio?

Usually cam lift is specified at the valve with a given rocker arm ratio. Since green67cuda is measuring at the valve spring retainer, it should match the cam specs. However, if you go the other way around and measure the cam lobe as I suggested, you would need to multiply it by the rocker arm ratio to get the total lift and compare that to the cam's specs.
 
DUH!!!
silly me....you can't accurately check lift and duration at the rocker or valve......the lifters bleed down, right??
*about* how much plunger travel do hydraulic lifters have????
 
Measure a few more you may find a variance of up to .010 lift between the lobes unless it's an older version ground in the USA and not by the lowest bidder as they are now.

We stopped using any MP Cams about 3-4 years ago after we profiled one and found .011 variance in lift and 4* variance in lobe separation ..kerr-plunk.....the sound of cast steel hitting the bottom of the blue plastic barrel. Clanl-clank....hummm must have hit a couple of Eddy carbs in there......:)
 
That barrel sounds like its getting full Don, I think you need to put a label on it. "Chevy Speed Parts" Might make a buck or two.
 
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