I am in the process of rebuilding a 403, does anyone know how to tune the distributer? I have the original G.M.unit that I have replaced the magnetic pick up, installed a MSD module with a rev limiter (to prevent a mistake), and a new MSD cap and rotor.I am going to replace the vacuum advance canister with an adjustable unit, I have been told to set the advance to 10 degrees all in by 3000 rpm. Is this right? What should the end play be between the gear and the housing? I have shimmed down to .050. Is this right?

 

That sure sounds like a chevy mechanic telling you what to do. Olds HEIs are set to have the initial 20° BTDC @ 1100 RPM. All in would vary on application.
You can get a weight kit to change the curve to mirror a points distributor and then the initial would be 8°-14° BTDC @ 1100 RPM depending on what the engine wants.

 

How do you adjust the vacuum advance?

 

When you replace the can there will be a small adjustment in the vacuum pipe on the can. You use the supplied allen wrench to adjust it.

 

Also shim for less than .050, that's still too much. I shoot for .015. Check to make sure you can lift the rotor the same amount once installed, that will ensure there is no binding.