Question on cam timing when you're ONE tooth off....

[Kern Dog]

Here we go....

Years ago I had a 318 in a Duster that was a S-L-U-G ! I tried all sorts of things to improve it but it was still slow. I pulled the timing cover to find that the cam sprocket and crank sprocket did not line up at the 6:00 firing position. With the crank at 12:00, the cam sprocket was off by at least one tooth.
Here is the question.....How much cam timing is in one tooth?
I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from?
I don't remember the amount of teeth on either sprocket. I'm also curious if the number of teeth is always the same no matter who makes the timing set. It is always a 2 to 1 ratio though since the crank sprocket is 1/2 the size of the cam sprocket.
If the cam sprocket could be rotated ONE tooth to line up to the crank sprocket, that is one thing. In theory, that is 1/2 tooth of timing at the crank, right?
This would mean that the cam sprocket could be off 1/2 of crank timing per cam sprocket with a chart as follows:
1 @ cam = 1/2 crank
2 @ cam = 1 crank
3 @ cam = 1 1/2 crank, etc.

Back to the Duster 318. This was in 2008 and the memory is a bit fuzzy. It was off the mark enough that the engine ran smooth but was gutless no matter how much spark timing was put to it. I tried different intakes, carburetors, distributors and even uncorked the exhaust. Once I put a new timing set in it, (Installed correctly) the car was great. Before, it wouldn't peel out even on light gravel over hard packed dirt.
What say you? What amount of cam timing difference do you see per tooth ?

 

[493 Mike]

Here we go....

Years ago I had a 318 in a Duster that was a S-L-U-G ! I tried all sorts of things to improve it but it was still slow. I pulled the timing cover to find that the cam sprocket and crank sprocket did not line up at the 6:00 firing position. With the crank at 12:00, the cam sprocket was off by at least one tooth.
Here is the question.....How much cam timing is in one tooth?
I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from? CAM SPROCKET
I don't remember the amount of teeth on either sprocket. I'm also curious if the number of teeth is always the same no matter who makes the timing set. It is always a 2 to 1 ratio though since the crank sprocket is 1/2 the size of the cam sprocket.
If the cam sprocket could be rotated ONE tooth to line up to the crank sprocket, that is one thing. In theory, that is 1/2 tooth of timing at the crank, right?
This would mean that the cam sprocket could be off 1/2 of crank timing per cam sprocket with a chart as follows:
1 @ cam = 1/2 crank
2 @ cam = 1 crank
3 @ cam = 1 1/2 crank, etc.

Back to the Duster 318. This was in 2008 and the memory is a bit fuzzy. It was off the mark enough that the engine ran smooth but was gutless no matter how much spark timing was put to it. I tried different intakes, carburetors, distributors and even uncorked the exhaust. Once I put a new timing set in it, (Installed correctly) the car was great. Before, it wouldn't peel out even on light gravel over hard packed dirt.
What say you? What amount of cam timing difference do you see per tooth ?

Human error is always a factor. If in doubt-degree the cam.
Mike

 

[Kern Dog]

Thanks....but that didn't answer the question about how many degrees are in each tooth on the sprockets.

 

[kiwigtx]

Here is the question.....How much cam timing is in one tooth?
I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from?
I don't remember the amount of teeth on either sprocket. I'm also curious if the number of teeth is always the same no matter who makes the timing set. It is always a 2 to 1 ratio though since the crank sprocket is 1/2 the size of the cam sprocket.

Count the teeth in the sprocket.

Divide that number of teeth into 360.

e.g. - 36 teeth would mean each tooth has 10 degrees.

I did the same thing for marking my dampener while waiting for timing tape to arrive.
My markings were so close to actual tape markings...there was nothing in it.

 

[Kern Dog]

Yeah, I am familiar with the math part of it. I just don't remember the amount of teeth on either sprocket.

It is hard to tell with the chain in place.

 

[Mackman]

I would guess that a cam retarded one tooth would have a more negative (negativer?) effect than a cam advanced by one tooth.

 

[dadeo]

Here's your answer. (near the middle)
Andy

 

[toolmanmike]

What was the question? And why?

 

[rickseeman]

Thanks....but that didn't answer the question about how many degrees are in each tooth on the sprockets.

On the roller type timing chains we use on BBM's there are 25 teeth on the crank sprocket and 50 on the cam sprocket.

 

[lewtot184]

It's more than counting teeth. Crank speed is double cam speed. One tooth either way is a bunch. Look at degree bushings and subtle change between zero and four, and then look at a single tooth; that's a bunch!

 

[rickseeman]

If you get the cam sprocket off 1 tooth your cam timing will be out 14.4 degrees. And that's way off. This is why a typical gear drive has a 7 position vernier. That way when your cam is off a little you can change it around 2 degrees per hole position. The RCD gear drive has an 11 position vernier.

 

[toolmanmike]

Here we go....

Years ago I had a 318 in a Duster that was a S-L-U-G ! I tried all sorts of things to improve it but it was still slow. I pulled the timing cover to find that the cam sprocket and crank sprocket did not line up at the 6:00 firing position. With the crank at 12:00, the cam sprocket was off by at least one tooth.
Here is the question.....How much cam timing is in one tooth?
I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from?
I don't remember the amount of teeth on either sprocket. I'm also curious if the number of teeth is always the same no matter who makes the timing set. It is always a 2 to 1 ratio though since the crank sprocket is 1/2 the size of the cam sprocket.
If the cam sprocket could be rotated ONE tooth to line up to the crank sprocket, that is one thing. In theory, that is 1/2 tooth of timing at the crank, right?
This would mean that the cam sprocket could be off 1/2 of crank timing per cam sprocket with a chart as follows:
1 @ cam = 1/2 crank
2 @ cam = 1 crank
3 @ cam = 1 1/2 crank, etc.

Back to the Duster 318. This was in 2008 and the memory is a bit fuzzy. It was off the mark enough that the engine ran smooth but was gutless no matter how much spark timing was put to it. I tried different intakes, carburetors, distributors and even uncorked the exhaust. Once I put a new timing set in it, (Installed correctly) the car was great. Before, it wouldn't peel out even on light gravel over hard packed dirt.
What say you? What amount of cam timing difference do you see per tooth ?

You'll never know where you're at until you degree the cam.

 

[rickseeman]

I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from?

360 divided by the number of teeth on the top sprocket (50) is 7.2. The camshaft turns 1/2 as fast as the crank. So when you check the timing (which you do on the crank) it is twice that much. 14.4 degrees.

 

[MWbirdLOVER70]

Yeah, I am familiar with the math part of it. I just don't remember the amount of teeth on either sprocket.

View attachment 1772858

It is hard to tell with the chain in place.

View attachment 1772859

Hey KD at that point just take the top bolt off and count but mark top gear before removing

 

[DeltaV]

Or, to phrase it differently. One complete cycle is 720 degrees since we are working with a 4-cycle engine. Being off by one out of 50 teeth on the camshaft sprocket is 720 degrees/50=14.4 degrees at the crankshaft like @rickseeman already replied @Kern Dog

 

[rickseeman]

You can count the teeth just the way it is. The lower sprocket is easier because you only have to count 1/2 as many. The pins in the rollers will help you.

 

[rickseeman]

I counted from your photo. 50 teeth on top so the lower is 25.

 

[DeltaV]

You'll never know where you're at until you degree the cam.

Agree.

Love this write-up from the Ed Iskenderian website:

Cam Degreeing

 

[Rebelrouser]

Here we go....

Years ago I had a 318 in a Duster that was a S-L-U-G ! I tried all sorts of things to improve it but it was still slow. I pulled the timing cover to find that the cam sprocket and crank sprocket did not line up at the 6:00 firing position. With the crank at 12:00, the cam sprocket was off by at least one tooth.
Here is the question.....How much cam timing is in one tooth?
I realize that you just divide the number of teeth on the sprocket by 360 but which sprocket do you do the math from?
I don't remember the amount of teeth on either sprocket. I'm also curious if the number of teeth is always the same no matter who makes the timing set. It is always a 2 to 1 ratio though since the crank sprocket is 1/2 the size of the cam sprocket.
If the cam sprocket could be rotated ONE tooth to line up to the crank sprocket, that is one thing. In theory, that is 1/2 tooth of timing at the crank, right?
This would mean that the cam sprocket could be off 1/2 of crank timing per cam sprocket with a chart as follows:
1 @ cam = 1/2 crank
2 @ cam = 1 crank
3 @ cam = 1 1/2 crank, etc.

Back to the Duster 318. This was in 2008 and the memory is a bit fuzzy. It was off the mark enough that the engine ran smooth but was gutless no matter how much spark timing was put to it. I tried different intakes, carburetors, distributors and even uncorked the exhaust. Once I put a new timing set in it, (Installed correctly) the car was great. Before, it wouldn't peel out even on light gravel over hard packed dirt.
What say you? What amount of cam timing difference do you see per tooth ?

If you want to set the chain without any marks, roll the engine to TDC, exact TDC use an dial indicator then roll the cam until you are on the overlap, exhaust closing and intake opening, put a small straight edge on the lifters it both lifters are at the same height the cam is heads up, if the intake is higher it is advanced, lower retarded. And when I say higher or lower just a few thousandths.

On the exact amount of degrees I do not know but they don't run right one tooth off it is at least 20 degrees.

 

[R/T Boy 67]

Cam installation specs are always in crank degrees. Advance a cam 4 degrees and the valves open 4 degrees sooner at the crank. Do the math on the crank sprocket to compare apples to apples.