OK, what the heck am I doing wrong?

Bobby Zlatkin · 11-10-2011, 02:19 PM

Secondary title to this post:
Don't trust your cam as you receive it and just install it and line up the marks.

This cam is supposed to be installed at 102 degrees.
When I checked it, it was at 112 degrees.
The cam manufacturer said it must have been ground wrong (mistakes happen) and to send it back. I checked the center line spacing and the lift and they were as they were supposed to be.

I don't want to take it out, send it back and wait for another one. So, I figure the cam gear has 36 teeth and each tooth is worth 10 degrees. If I move it one tooth it will bring it to 102 degrees and I could fine tune it from there with three positions of the crank gear.

However, when I move it one cam gear tooth, it moves it 20 degrees to 92 degrees. I tried it back and forth several times with the same results.

What am I figuring/doing wrong?

Jim B · 11-10-2011, 02:52 PM

Cam specs are listed in crankshaft degrees. Since the cam spins at 1/2 engine speed one 360º cam rotation takes 720 º of crankshaft rotation. Hence 10º of cam rotation results in 20º of crankshaft rotation. If you suspect the cam may be ground wrong be sure to double check the cam centerline. If that checks to specs the dowel location is wrong on the camshaft and advancing the cam 10º (crankshaft) in your scenario would be OK. (the intake 112º would become 102º but don't forget the exhaust lobe is going to move 10º retarded)

Jim Kaekel · 11-10-2011, 02:52 PM

Bobby: You just need to get a set of offset cam degree bushings like those that Comp, Crane, etc. sell. Drill the cam gear so that it will accept a bushing and start from there. You may have to try a couple of different bushings to get to the manufacturer's recommended intake centerline. Follow the manufacturer's instructions regarding degreeing the cam. It's usually listed right on the cam card. A timing set such as the Cloyes Hex-a-Just makes this process very easy.

Alan Roehrich · 11-10-2011, 03:01 PM

Jim is right.

It is also common to find timing sets that are marked wrong, I have found them myself, the key ways in the crank gear were not correctly marked.

I prefer the "Fast-A-Just" Cloyes set. I use the crank gear to get the set baselined so that with the cam gear set to zero, the cam is either straight up, or advanced per the grinder's instructions. Then I move the cam with the cam gear.

If you use a "Hex-A-Just", make certain you back off every rocker before making an adjustment, or you'll be calling Cloyes to get a new hex bushing. In fact, I'd call and by a spare or two to keep with the car, before I ever put one on.

Ed Wright · 11-10-2011, 03:53 PM

I bought one of those once. Took one look at the hex-adjust bushing and tossed it on the shelf. If this is a SBC, get yourself a Rollmaster set. Nicest deal I've seen. Has advance & retard key ways in the crank gear. No cast gears either. I found one tooth on a regular SBC set is more like 22 deg.

Bobby Zlatkin · 11-10-2011, 05:32 PM

Jim K: An offset bushing won't do it for me. They can give you 4 - 6 deg. and I need more than that.

I have a Speed Pro timing gear set with a 3 keyway crank gear. But again, that doesn't give me enough.

I understand that the crankshaft teeth are 20 deg. each and the cam gear teeth are 10 deg. each.

What I don't understand is how moving the cam gear one tooth moves the cam 20 deg. I never was very good at math, but this is something I just can't get my head around.

art leong · 11-10-2011, 06:16 PM

Quote:

Originally Posted by Bobby Zlatkin

Jim K: An offset bushing won't do it for me. They can give you 4 - 6 deg. and I need more than that.

I have a Speed Pro timing gear set with a 3 keyway crank gear. But again, that doesn't give me enough.

I understand that the crankshaft teeth are 20 deg. each and the cam gear teeth are 10 deg. each.

What I don't understand is how moving the cam gear one tooth moves the cam 20 deg. I never was very good at math, but this is something I just can't get my head around.

10 crankshaft degrees are 20 camshaft degrees. The cam or cams rotate at half the crank speed.
On my motor one cam gear tooth is 18 degrees. But it is only 9 crankshaft degrees. So I I'm a tooth off I'm off 9 degrees. This was easy in my case due to cutting the block and head. The marks were wrong in either direction. Had to move the cams a bunch to get them both straight up. With 2 cams it is harder because you line up the intake, but that doesn't mean the exhaust is right. I was running for a year with my exhaust cam 9 degrees (one tooth) retarded.

Jim B · 11-10-2011, 07:15 PM

As several posts put together suggest, you should be able to come up with 10º by combining offset crank gears/keyways and cam offset bushings. What is the cam lobe centerline supposed to be on your cam? How does it check with a known good gear/chain setup? If it checks to spec (I would heartily recommend you check the cam lobe centerline) you will have to either double check the gearset, use the above combo, or have the cam replaced to solve the problem. Since it's not a DOHC motor you don't have the ability (like Art for example) to change the cam lobe center without changing the camshaft. As far as wrapping your head around the 10-20 degree concept, don't fret about it - usually a good nights' sleep lights the light bulb the next day and it magically becomes clear as day. Just think about it as a 1:2 overdrive setup...one cam revolution (360º ) drives the crank two revolutions (720 º )

eddie c · 11-10-2011, 07:22 PM

Quote:

Originally Posted by art leong

10 crankshaft degrees are 20 camshaft degrees. The cam or cams rotate at half the crank speed.
On my motor one cam gear tooth is 18 degrees. But it is only 9 crankshaft degrees. So I I'm a tooth off I'm off 9 degrees. This was easy in my case due to cutting the block and head. The marks were wrong in either direction. Had to move the cams a bunch to get them both straight up. With 2 cams it is harder because you line up the intake, but that doesn't mean the exhaust is right. I was running for a year with my exhaust cam 9 degrees (one tooth) retarded.

Art; I thought that I understood this,but now I am confused. You state 10 crank degrees equal 20 cam degrees. Since the cam moves half of the crank,wouldn't 10 crank degrees equal 5 cam degrees? help to explain
this please. ed

STK1217 · 11-10-2011, 08:11 PM

Try 4 deg. adv. on crank key and 2 deg. adv. on cam bushing.

11-10-2011, 02:19 PM	#1
Bobby Zlatkin Member Join Date: Mar 2003 Location: Mills River, NC Posts: 417 Likes: 0 Liked 0 Times in 0 Posts	OK, what the heck am I doing wrong? Secondary title to this post: Don't trust your cam as you receive it and just install it and line up the marks. This cam is supposed to be installed at 102 degrees. When I checked it, it was at 112 degrees. The cam manufacturer said it must have been ground wrong (mistakes happen) and to send it back. I checked the center line spacing and the lift and they were as they were supposed to be. I don't want to take it out, send it back and wait for another one. So, I figure the cam gear has 36 teeth and each tooth is worth 10 degrees. If I move it one tooth it will bring it to 102 degrees and I could fine tune it from there with three positions of the crank gear. However, when I move it one cam gear tooth, it moves it 20 degrees to 92 degrees. I tried it back and forth several times with the same results. What am I figuring/doing wrong? __________________ Bobby & Norene Zlatkin L/SA

11-10-2011, 02:52 PM	#2
Jim B Member Join Date: Dec 2008 Posts: 100 Likes: 0 Liked 1 Time in 1 Post	Re: OK, what the heck am I doing wrong? Cam specs are listed in crankshaft degrees. Since the cam spins at 1/2 engine speed one 360º cam rotation takes 720 º of crankshaft rotation. Hence 10º of cam rotation results in 20º of crankshaft rotation. If you suspect the cam may be ground wrong be sure to double check the cam centerline. If that checks to specs the dowel location is wrong on the camshaft and advancing the cam 10º (crankshaft) in your scenario would be OK. (the intake 112º would become 102º but don't forget the exhaust lobe is going to move 10º retarded) Last edited by Jim B; 11-10-2011 at 02:58 PM.

11-10-2011, 02:52 PM	#3
Jim Kaekel VIP Member Join Date: Jul 2002 Location: Michigan Posts: 1,229 Likes: 133 Liked 535 Times in 110 Posts	Re: OK, what the heck am I doing wrong? Bobby: You just need to get a set of offset cam degree bushings like those that Comp, Crane, etc. sell. Drill the cam gear so that it will accept a bushing and start from there. You may have to try a couple of different bushings to get to the manufacturer's recommended intake centerline. Follow the manufacturer's instructions regarding degreeing the cam. It's usually listed right on the cam card. A timing set such as the Cloyes Hex-a-Just makes this process very easy. __________________ Jim Kaekel 3836 STK

11-10-2011, 03:01 PM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,577 Liked 1,837 Times in 417 Posts	Re: OK, what the heck am I doing wrong? Jim is right. It is also common to find timing sets that are marked wrong, I have found them myself, the key ways in the crank gear were not correctly marked. I prefer the "Fast-A-Just" Cloyes set. I use the crank gear to get the set baselined so that with the cam gear set to zero, the cam is either straight up, or advanced per the grinder's instructions. Then I move the cam with the cam gear. If you use a "Hex-A-Just", make certain you back off every rocker before making an adjustment, or you'll be calling Cloyes to get a new hex bushing. In fact, I'd call and by a spare or two to keep with the car, before I ever put one on. __________________ Alan Roehrich 212A G/S

11-10-2011, 03:53 PM	#5
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: OK, what the heck am I doing wrong? I bought one of those once. Took one look at the hex-adjust bushing and tossed it on the shelf. If this is a SBC, get yourself a Rollmaster set. Nicest deal I've seen. Has advance & retard key ways in the crank gear. No cast gears either. I found one tooth on a regular SBC set is more like 22 deg. __________________ Ed Wright 4156 SS/JA

11-10-2011, 05:32 PM	#6
Bobby Zlatkin Member Join Date: Mar 2003 Location: Mills River, NC Posts: 417 Likes: 0 Liked 0 Times in 0 Posts	Re: OK, what the heck am I doing wrong? Jim K: An offset bushing won't do it for me. They can give you 4 - 6 deg. and I need more than that. I have a Speed Pro timing gear set with a 3 keyway crank gear. But again, that doesn't give me enough. I understand that the crankshaft teeth are 20 deg. each and the cam gear teeth are 10 deg. each. What I don't understand is how moving the cam gear one tooth moves the cam 20 deg. I never was very good at math, but this is something I just can't get my head around. __________________ Bobby & Norene Zlatkin L/SA

11-10-2011, 07:15 PM	#8
Jim B Member Join Date: Dec 2008 Posts: 100 Likes: 0 Liked 1 Time in 1 Post	Re: OK, what the heck am I doing wrong? As several posts put together suggest, you should be able to come up with 10º by combining offset crank gears/keyways and cam offset bushings. What is the cam lobe centerline supposed to be on your cam? How does it check with a known good gear/chain setup? If it checks to spec (I would heartily recommend you check the cam lobe centerline) you will have to either double check the gearset, use the above combo, or have the cam replaced to solve the problem. Since it's not a DOHC motor you don't have the ability (like Art for example) to change the cam lobe center without changing the camshaft. As far as wrapping your head around the 10-20 degree concept, don't fret about it - usually a good nights' sleep lights the light bulb the next day and it magically becomes clear as day. Just think about it as a 1:2 overdrive setup...one cam revolution (360º ) drives the crank two revolutions (720 º ) Last edited by Jim B; 11-10-2011 at 07:24 PM.

11-10-2011, 08:11 PM	#10
STK1217 Member Join Date: Nov 2006 Posts: 137 Likes: 48 Liked 10 Times in 7 Posts	Re: OK, what the heck am I doing wrong? Try 4 deg. adv. on crank key and 2 deg. adv. on cam bushing.