Cam timing with a degree wheel (7AGE specifically)

[70XIN]

Hi guys,

I'm currently working on a friends' 7AGE motor, we're up to doing cam timing.

I worked out 'true' TDC with a dial indicator and a degree wheel, but i can't seem to find the correct formula for working out the cams lobe centre (they are just standard cams, so should be 110deg)

I've been using this example (and others) but none seem to get anywhere right: http://www.skylinesaustralia.com/for...s-t240804.html

I've set the cams ROUGHLY in their correct positions, but i'm getting results like 150 degrees... I'm using the "valve opening and closing at 0.050" lift"

Can anyone tell me the right way to do this?

Thanks

[tojo]

Go to a cam makers website (ex kentcams) They usually have a decent writeup on howto.

Lots easier to understand than me trying to explain : )

[70XIN]

I've used various cam writeups/programs, but they don't seem to be for DOHC motors, i dont know if that matters...

Anywho, for example, i went and measured the inlet opening/closing at 0.050", i got:

Open - 14 degrees atdc

Close - 144 degrees abdc

Which gives me a lobe centre of 155 degrees

I then tried the 0.040" and got the exact same end result (which i should!)

11.5 degrees
141.5 degrees

= 155 degrees.


Now i'm POSITIVE i have the crank at TDC, and there is a "marking" on the inlet cam of 4AGE motors that tells you if you're in the general vicinity of TDC.. so in THEORY i should be at least close.. but i'm still getting those wack results

Has anyone got a definitive 'equation' for a 4AGE/7AGE/similar motor?

[70XIN]

Okay, i found another site that uses a different formulae

http://www.camshafts.co.nz/CamDegreeing.aspx

Using it, i got 79 degrees. A figure slightly more advanced i did earlier in the day got me 90.5 degrees, and a measurement i just took then (18deg open, 172deg closed) gives me 100deg lobe seperation.. That's with the cam gears at "full advance"

If this is the right formula, id be very happy, it means i just have to go back (or forwards) a tooth on the cam gear/s, and adjust.

Can anyone shed some light?

[70XIN]

Aaaand i have my answer, the second method is indeed the correct one

Cheers guys

[50RTD]

Cheers for the link/s, something i've wanted to try and get my head around for a while.

So much maths, for such a small brain!