I have the comp cams xe268. I was wondering how much of an rpm difference there is for say 4 degrees. I have a 3000 stall converter and thought that I might go retard it 4 degrees so it would be straight up or however it is termed. In order to do this do I need a special timing set? I was wondering if there is a rule of thumb for how many degrees a tooth changes it on a timing set or if I absolutely need a degree wheel? Any info you guys have would be great. Also how much does a degree wheel cost, and if I need a special timing set what exactly do I need and how much does it cost?

Thanks

Ben

 

I wouldn't mess with it.

Comp Cams has put a lot of money into making there cams perform at a certain amount of advance. The only way you should mess with it is if you have access to a dyno and you can experiment with different settings.

The way you can do it is by using a timing chain set that has 3 keyways in the crank sprocket. They're usually not too expensive. Cloyes and Milodon have sets that range right around $20. Each keyway has a set marking on it. One's for "straight up", one's for advance 4*, and the other's for retard 4*.

DO NOT!!!! try changing the settings by skipping a tooth. This is a very "hit or miss" method and that refers to whether or not the valves hit or miss the pistons.

Any good engine builder, as well as some that are simply engine assemblers, will check the cam by using a degree wheel. All this does is reduce the chance that the cam company made a mistake of either setting the timing wrong, or they sent you the wrong cam.

The normal rule of thumb for street machines is to advance the timing 4*. This provides a little more low/midrange torque which gives the tire shredding power that most people want out of a street machine.

However, if this provides any improvement at all, either way, it really means the wrong cam has been used compared to the rest of the combo.

 

Any result from moving the cam 4 deg will be
small . A ll it does is shift the power (torque curve up or down within the same rpm range.
the only real way to ttell if it actually will help your car accelerate
is a direct before and after test at the drag strip.

Even a dyno test will not tell you if the change actually helped
*your car* or not. It will only tell you what it did on the dyno.
Generally speaking these cams are already in the optimum spot
as made. Not a lot to gain there.

If any thing I would experiment with advanceing it further
to increase cylinder pressure and overall average torque output.

You have two methods to move the cam .
1. get a multi keyway crank timing gear. ( comes in a set)
2. get a cam gear offset bushing set and locking plate.( Crane, Mr Gasket).

You can't just skip the gear over 1 tooth, it will move the cam way too far. +/-10 to 20 deg.