cam degreeing confusion

Posted By: JerseyJoe

cam degreeing confusion - 03/16/12 08:30 PM

I'm using intake centerline method, when measuring at .050 valve lift does my dial need to be on the lifter or can it be on the valve retainer(factoring in my 1.5 ratio rockers)?

I keep coming up with the same TDC but @ .050 (dial on the valve retainer) I'm not getting anywhere near the 106 centerline on the cam card.
Any help is appreciated, Joe

Posted By: Clanton

Re: cam degreeing confusion - 03/16/12 09:51 PM

it would be good to measure both ways lifter/retainer and the lifter method would show the most accurate/true cam and you would adjust the retainer reading to match the ICL you want with the crank gear.

Posted By: Cab_Burge

Re: cam degreeing confusion - 03/16/12 10:17 PM

Quote:

I'm using intake centerline method, when measuring at .050 valve lift does my dial need to be on the lifter or can it be on the valve retainer(factoring in my 1.5 ratio rockers)?
I keep coming up with the same TDC but @ .050 (dial on the valve retainer) I'm not getting anywhere near the 106 centerline on the cam card.
Any help is appreciated, Joe

checking the LSA can be done on the lifter or the retainer, checking the CAM SPECS. can ONLY be done on the lifter as that is what the cam grinder bases their specs on, cam lift at the liter, not at the retainer

I like to do the LSA at the retainer as the motor knows what the valves are doing, it doesn't know what the lifter is doing

The rocker ratio will make all the cam specs. read at the retainer wrong be the amount of the ratio, IE 1.5 ratio will have more lift and duration at the retainers than at the lifters, a 1.8 ratio will have even more

BTW, I like to check the LSA on the exhaust sides to verify that the intake side and the exhaust sides are truly ground like the cam card calls for, IE if straight up on a 110 LSA both lobes should be in at 110, if advanced two degrees on the intake, in at 108 ATDC then the exhaust should be in at 112 BTDC

IHTHs

Posted By: lewtot184

Re: cam degreeing confusion - 03/16/12 10:59 PM

Quote:

I'm using intake centerline method, when measuring at .050 valve lift does my dial need to be on the lifter or can it be on the valve retainer(factoring in my 1.5 ratio rockers)?
I keep coming up with the same TDC but @ .050 (dial on the valve retainer) I'm not getting anywhere near the 106 centerline on the cam card.
Any help is appreciated, Joe

if you have a true 1.5 rocker multiply .050x1.5 and thats the cam lobes .050 number at the valve. you cannot check duration, lift, or anything for that matter using a hydraulic lifter. best, and simpiliest is check at the lobe.

Posted By: JerseyJoe

Re: cam degreeing confusion - 03/17/12 12:47 AM

Thanks for the replies, I should have given more info. It's a RB motor and an XS290S Comp Cam, solid lifter and Crane ductile iron rockers. It was late last night and my math is shaky anyway, so I missed the .050 x 1.5 rocker part.

Posted By: 440newport

Re: cam degreeing confusion - 03/17/12 06:43 PM

The first time I degreed a cam I wasn't coming up with anything close to what it was supposed to be either.

It took me a while to realize I was trying to degree it from the #1 exhaust lobe instead of the intake.

Posted By: Stanton

Re: cam degreeing confusion - 03/17/12 09:51 PM

Forget about the rocker ratio, it is totally insignificant. Measuring at the retainer all you want to do is make sure whatever reading you take on the upstroke is the same on the downstroke. So, if you use .075 on the upstroke, use .075 on the downstroke.

Now, since all this is dependent on an accurate TDC, how did you do that with the heads on?

And if you're checking at the retainer, make damn sure the shafts are bolted down tight.

Posted By: JerseyJoe

Re: cam degreeing confusion - 03/18/12 02:11 AM

I found it. A bonehead, rookie mistake. I have a Comp Cams crank sprocket with the "O" on the keyway as well as the timing mark. Guess which one I lined up with the cam sprocket...

I'm using the directions from Comp Cams, including a piston stop to find TDC. They're similar to other cam companies' directions, is this not the way to go?

Posted By: Stanton

Re: cam degreeing confusion - 03/18/12 02:38 AM

Quote:

including a piston stop to find TDC

was just checkin'

Posted By: Cab_Burge

Re: cam degreeing confusion - 03/18/12 03:36 AM

Quote:

I found it. A bonehead, rookie mistake. I have a Comp Cams crank sprocket with the "O" on the keyway as well as the timing mark. Guess which one I lined up with the cam sprocket...

I'm using the directions from Comp Cams, including a piston stop to find TDC. They're similar to other cam companies' directions, is this not the way to go?

Dude, your not the only one that has done that

Check the lobe centers on both valves