cam timing ?'s

SSDiv6 · 07-20-2010, 11:02 PM

Quote:

Originally Posted by rod

i bought a new cam. and now i don't understand the figures. bare with me
the card shows [let's deal with intake only] open at 21, close at 61 and 108 CL. that is exactly what the cam checks out to be.
however 21+61+180=262 divided by 2=131-21 =110.
i have checked and rechecked. i cannot get the CL to get on 110.
either one side is asymetrical or i am crazy.
what i don't understand is this. is the cam now advanced 2 degrees [the Jesel belt pulley is on 0], or is it straight up?
my desktop dyno shows most power at 108CL. so i am fine with it being there [that is the CL at 108].
i just want to know where it really is.
thoughts?
thanks
rod in AZ

Coul you scan and post the cam card with the the information?

Adger Smith · 07-27-2010, 09:44 PM

Rod,
There are 2 centerlines to a cam. Intake C/L.. Ex C/L and then there is Lobe separation. When the cam is ground the lobe separation is set. Period. you can't alter it. The intake centerline can be placed. By that I mean you can install a cam with the intake C/L where you want it. The ex C/L will follow where you put the I C/L by the number of degrees of lobe separation, Intake C/L to Ex C/L...
Every cam company puts the Lobe separation on the cam card. It can be mixed up for intake centerline. Cams can be ground with the intake C/L moved forward on the dowel pin. Most cam Co's mark that as a +2 or +4 or whatever. Without knowing the brand or seeing your card I'm operating a little blind on this. If you want the cam in @ 108 I C/L degree it that way by the .050 over the nose method. Forget the numbers you are trying to juggle. It will be @ 108 if you put it there.

another note.. Don't believe those dots and numbered slashes on Jesel belt drives. They are very bad about being off a few degrees either way. I consider them as reference points.. Only..

BlueOval Ralph · 07-28-2010, 05:33 AM

When the cam is ground the lobe separation is set. Period. you can't alter it.

Unless you have a new Viper which has what is known as Cam in Cam then centerline CAN be changed as engine is running.. Check into this new tech.

Quote:

Originally Posted by Adger Smith

Rod,
There are 2 centerlines to a cam. Intake C/L.. Ex C/L and then there is Lobe separation. When the cam is ground the lobe separation is set. Period. you can't alter it. The intake centerline can be placed. By that I mean you can install a cam with the intake C/L where you want it. The ex C/L will follow where you put the I C/L by the number of degrees of lobe separation, Intake C/L to Ex C/L...
Every cam company puts the Lobe separation on the cam card. It can be mixed up for intake centerline. Cams can be ground with the intake C/L moved forward on the dowel pin. Most cam Co's mark that as a +2 or +4 or whatever. Without knowing the brand or seeing your card I'm operating a little blind on this. If you want the cam in @ 108 I C/L degree it that way by the .050 over the nose method. Forget the numbers you are trying to juggle. It will be @ 108 if you put it there.

another note.. Don't believe those dots and numbered slashes on Jesel belt drives. They are very bad about being off a few degrees either way. I consider them as reference points.. Only..

Adger Smith · 07-28-2010, 07:04 AM

You are exactly correct about the "New technology" I could have gone on about that or dual overhead cams, but I don't think that he is working on either one of those. I think you will notice I ask, as well as SS Div 6, ask about or to see the cam card. That would have helped identify what he is working on.
I could have also told him: whats the big deal with the cam? It's "at the valve" that the engine sees.
I could have gone on and on about finding cams that aren't ground as the spec card says (very common) when profiling them on Cam Pro Plus or a Cam Dr. I could have explained that the actual grinding diameter of the grinding wheel on some of the Non Computer grinders makes the cam profile different from the master profile. Computer grinders usually have "Compensation" programed in.
Just follow the KISS program, put it in at 108, I didn't want it to be any more confusing than it already is.

07-27-2010, 09:44 PM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: cam timing ?'s Rod, There are 2 centerlines to a cam. Intake C/L.. Ex C/L and then there is Lobe separation. When the cam is ground the lobe separation is set. Period. you can't alter it. The intake centerline can be placed. By that I mean you can install a cam with the intake C/L where you want it. The ex C/L will follow where you put the I C/L by the number of degrees of lobe separation, Intake C/L to Ex C/L... Every cam company puts the Lobe separation on the cam card. It can be mixed up for intake centerline. Cams can be ground with the intake C/L moved forward on the dowel pin. Most cam Co's mark that as a +2 or +4 or whatever. Without knowing the brand or seeing your card I'm operating a little blind on this. If you want the cam in @ 108 I C/L degree it that way by the .050 over the nose method. Forget the numbers you are trying to juggle. It will be @ 108 if you put it there. another note.. Don't believe those dots and numbered slashes on Jesel belt drives. They are very bad about being off a few degrees either way. I consider them as reference points.. Only.. __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-27-2010 at 09:53 PM. Reason: sp

07-28-2010, 07:04 AM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: cam timing ?'s You are exactly correct about the "New technology" I could have gone on about that or dual overhead cams, but I don't think that he is working on either one of those. I think you will notice I ask, as well as SS Div 6, ask about or to see the cam card. That would have helped identify what he is working on. I could have also told him: whats the big deal with the cam? It's "at the valve" that the engine sees. I could have gone on and on about finding cams that aren't ground as the spec card says (very common) when profiling them on Cam Pro Plus or a Cam Dr. I could have explained that the actual grinding diameter of the grinding wheel on some of the Non Computer grinders makes the cam profile different from the master profile. Computer grinders usually have "Compensation" programed in. Just follow the KISS program, put it in at 108, I didn't want it to be any more confusing than it already is. __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-28-2010 at 07:07 AM. Reason: sp