just degreed my cam and its out - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-25-2009, 10:24 PM
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just degreed my cam and its out

ok71 vega.383,10.25:1 comp,holly 750 vac sec,dart 180 heads mild porting,
auto trans,performer rpm manifold
my porting guy sold me a cam hydrolic roller
intake .540 dur@.050 233
ex .540 dur @.050 242
after checking with degree wheel and dial indicator intake is off by 5.5 degres
exaust by 4 degres and when i mesure lobe lift i get
intake .357 which is close .357x1.5=.535 but exhast difrent story
.371 .371x1.5= .5567 abit more than .540
my opinion is what a bunch of cr p! but im no expert
the guy said it was a custum grind ,by who i dont know it come in a plain white box what do you guys think?
thankyou vegadude

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Last edited by johnbelanger; 05-25-2009 at 10:26 PM. Reason: typo
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Old 05-25-2009, 11:03 PM
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When you say off are we talking 5.5 degrees advanced or retarded? Or is the total duration at .050 bigger or smaller by 5.5 degrees?

I would not expect the lift to be the same on lobes with different durations.
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Old 05-25-2009, 11:36 PM
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Quote:
Originally Posted by johnbelanger
ok71 vega.383,10.25:1 comp,holly 750 vac sec,dart 180 heads mild porting,
auto trans,performer rpm manifold
my porting guy sold me a cam hydrolic roller
intake .540 dur@.050 233
ex .540 dur @.050 242
after checking with degree wheel and dial indicator intake is off by 5.5 degres
exaust by 4 degres and when i mesure lobe lift i get
intake .357 which is close .357x1.5=.535 but exhast difrent story
.371 .371x1.5= .5567 abit more than .540
my opinion is what a bunch of cr p! but im no expert
the guy said it was a custum grind ,by who i dont know it come in a plain white box what do you guys think?
thankyou vegadude
I wouldn't be too worried about the lift as long as the valves do not hit the pistons. In the past to properly degree a cam I have checked the duration on all eight cylinders for each valve. Some would be early some would be late. I would write down the numbers and then I would decide if the cam needed to be advanced or retarded and if it could be brought closer to the cam grinders spec's. Most of the time it turns out to be a compromise. You find the pair that is the farthest retarded and the pair that is farthest advanced and use the offset timing to try and bring them together and as close to the cam spec's as you can. Like I said it turns out to be a compromise. I have found some cams to be so far out that I could not get them close enough to use in a race engine. These cams either went back to the person that I bought them from or wound up in a street/show car. As far as the cam that you have being a good choice for your intake, heads, transmission and weight of car, I will have to let some one else answer that. There has been a lot of improvement in cams over the last few years and I haven't kept up with it. But you do need to check all sixteen. And a simple way to check valve to piston clearance is with modeling clay. Just put the engine together with used head gaskets of the same type that you plan to use and put a little bit of clay on top of each piston, spray some silicon or light oil on top of the clay and the face of the valves and combustion chamber so it wont stick to the valves and the chamber. Turn the engine over by hand several times, take the heads off and the slice through the clay with a razor blade where the valves have imprinted it and measure the thickness of the clay in that area.

I hope this helps
Chris

Last edited by Chris Kemp; 05-25-2009 at 11:41 PM.
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Old 05-26-2009, 01:02 AM
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here are timing numbers spec say
intake opens 6.5btdc closes 46.5abdc
ex opens 51bbdc closes 11 atdc
this is what i measured
intake opens 12 closes 41
ex opens55 closes 7

i wonder why they advertise its .540/ .540 when its more like .540/ .555
to me it seems intake is late and so is exaust?

Last edited by johnbelanger; 05-26-2009 at 01:12 AM.
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Old 05-26-2009, 02:32 AM
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Going by your #'s everything is early, or advanced. Are you sure you aren't using the +4 degree setting on the timing chain set, if it has one?

Right now you are installed on a 104.5 degree intake centerline from a listed 110 degree lobe centerline and the cam is ground with a 109 degree lobe seperation.

If the piston to valve clearance is good, I would leave it there.
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Old 05-26-2009, 09:26 AM
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i set it at zero,now that the holidays over i can call the shop i bought it from
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