I just got a new cam shaft in the mail from Summit, for my '72 302, and was reading the installation instruction when I came across the following:

"For 1972 and later Ford-Mercury V8 engines with retarded crankshaft sprocket, it is necessary to either "degree" the camshaft or use a non-retarded, pre-1972 crankshaft sprocket to avoid idle and performance problems"

What is this all about? Why would Ford use a retarded crankshaft sprocket? What does it mean to "degree" the camshaft?

Thanks

 

http://www.rpmrons.com/degreecam.html This site will give you the details on how to degree in your cam. Retarded sprockets were used to meet environmemtal restrictions.

 

I think that was done for smog. To degree the cam means to attach a large degree wheel to the crank. You can then find out if the cam is opening the valves when it is supposed to. Some cam sprockets have a means of adjusting the timing relationship. You have to accurately find TDC to degree the cam.

 

Engine performance is critically tied to several timing factors, and cam timing is one of them. Valve opening, duration of the open time, and closing is measured as part of the 360 degree rotation of the camshaft - a circle.
Late opening, early opening, long or short duration all affect performance, and will affect power, performance and emissions.
This is the concept of the differences bwteeen RV cams, power cams, mileage cams, etc. They have differing lobes, with differing degrees of activation upon the valves.
For example, in the early smog years, Mopar products used an overlapping valve timing to control emissions, instead of an EGR vavle. The cam was designed to keep the exhaust valve open just a bit longer, and remain open for a few degrees while the intake was open. This allowed the intake to suck in some exhaust to reduce NOx.Eventually, they went to EGR valves because it was more flexible. They, and all the other car makers eventually had to eliminate or severely reduce the produciton of the big and pwerful engines for John Q. Public to meet emissions standards. Of course, all of this robs power and mileage.
The point of all this is that you can purchase aftermarket cam gears with multiple camshaft key slots. This allows you to set your cam timing advanced or retarded as desired. When coupled with a power cam, an RV cam, etc, you can have a wide range of possibilities.

 

Quote:
>Valve opening, duration of the open time, and closing is measured as >part of the 360 degree rotation of the camshaft - a circle.

Actually it is measured on crankshaft degrees. There are a few race cams out there with more than 360 degrees of advertised duration if you don't believe me.

Quote:
>Mopar products used an overlapping valve timing to control >emissions, instead of an EGR vavle. The cam was designed to keep >the exhaust valve open just a bit longer, and remain open for a few >degrees while the intake was open. This allowed the intake to suck
>in some exhaust to reduce NOx.

I'm not getting this statement. The bigger the duration and the smaller the LCA (hotter cam) the more overlap there is. Only very small economical and emmisions friendly cams have little or no overlap.

Quote:
>The point of all this is that you can purchase aftermarket cam gears >with multiple camshaft key slots. This allows you to set your cam >timing advanced or retarded as desired.

He will still have to get a pre 72 timing set as the later ones have about 8 degrees of retard built into them. The different keyways will only allow 2 - 4 degrees wither way.

 

[updated:LAST EDITED ON 22-Dec-02 AT 01:33 PM (EST)]How would you know if you are getting a pre 72 set? There must be a way to measure the amount of retard before you install it, thanks.

 

They sell them as pre 72 or 72 and earlier.

 

The specification sheet that came with the camshaft will tell you if it is ground retarded or not. If the cam is not ground retarded this adjustment is made with the crank sprocket. You can see where the key way is not directly under the timing mark. Cloys true roller timing chain set has three keyways to make these adjustments. Most likely your cam is cut 4 degrees retarded and using the Cloys crank sprocket set cam timing straight up.
William in Atlanta

 

When I got the thing apart it turns out to be a mute point because I do not have a retarded timing gear. The way you can tell a retarded crankshaft timing gear is if the dot is not lined up with the key slot in the gear. With a non-retarded gear the slot and dot line up. Anyways mine line up so I have non-retarded timing.

If I would have had retarded timing then the instructions say to use a non-retarded timing set with my new cam.