Cam Timing

dan adams · #1 (**permalink**) 08-20-2002, 08:02 PM

I am timing my cam. It is a M-6250-C460 Ford motorsports cam.
.595 int. lift , .621 exh. lift, 310 & 320 duration w/95 duration.
Using a Cloyes roller chain. It has three key positions, at 2 degree increments.
Cam card says at .006 lift, int. should open at 48 deg. and close
at 82.
The closest I could get was open at 47 and close at 79. This was achieved at the retard setting on the small gear.
Each move of the keyway changed 5 degrees, not 2 degrees as the manufacture stated. Is this a result of the higher duration?
Exhaust side had similar results. Seems the actual duration is less than stated by Ford? Lift was very close to advertised.
Has anyone else had much experience with really looking at cam
timing? I have build four other motors as a kid, just lined up the dots and let it go. Turbo VWs (2) and a couple...well lets just say other V8s. Dan

Mr.Fixit · #2 (**permalink**) 08-21-2002, 09:29 AM

So the numbers you are measuring are not exactly what are printed on the cam card, how normal. This is why you must degree you camshaft, to get it timed correctly and to make sure it is opening and closing at the right times. The 5 degrees verses 2 degrees: 5 degrees on the crankshaft is 2.5 degrees on the camshaft, is that it? Were they giving that number in "cam degrees"?

Andy Dunn · #3 (**permalink**) 08-21-2002, 09:43 AM

Here is a great paragraph from the Crane website

It is the exception, rather than the rule, that a cam may be out of phase, but this should be established to insure an accurate performance baseline or point of tune.

WHY DEGREE-IN YOUR CAM
The purpose of degreeing a cam is to insure that the cam is phased correctly with the crankshaft, per the cam manufacturers’ specifications. Some factors that may cause improper phasing are:

1. Cam or crank gears are incorrectly marked.
2. Keyways are out of position on gears.
3. Keyway in the crankshaft is misindexed.
4. Cam dowel pin or keyway is misindexed.

Here are some great tutorials on degreeing cams from the major manufacturers. They are all just a little bit different.

Crane
http://www.cranecams.com/instruction...ing/degree.htm

Lunati
http://www.holley.com/HiOctn/TechSer...IECCTech8.html

Isky
http://www.iskycams.com/degreeing.html

Comp
http://www.compcams.com/catalog/022.html
http://www.compcams.com/catalog/023.html

Hope this info helps =)

Andy

dan adams · #4 (**permalink**) 08-21-2002, 05:46 PM

Mr. Fixit,
Yes, I had not thought of that. 2 degrees on the small gear
may get you 4 on the degree wheel. If so that clears up alot.
Thanks, Dan

dan adams · #5 (**permalink**) 08-21-2002, 05:48 PM

Andy, thanks for the sites. I'll go read and run through things a few more times. Dan

mickmate · #6 (**permalink**) 09-04-2002, 08:30 AM

Andy, thanks for the links that's good stuff. I wonder if anyone reading this has tried it on their motor, how far out they are assembled to and the biggie is how much difference does it really make in practice (obviously dependent on how far they were out to start with). Just curious as I'm trying the Comp Cam Centreline method on "ANOTHER" brand at the moment.
Cheers