Yes the 9.5 on the arm is saying that you can get a max of 19 degrees . The allen hex in the end of the nipple regulates how much vacume it takes to get that. The more counter clock wise you go the higher the vacume will need to be to reach the amount of advance you want. Clock wise will make it take less vacume to get the unit to move. Your right the more initial timing the motor will run cooler. But I would do that with the advance slot in the distributor. Then play with the vac can. www.4secondsflat.com has a new no welding required advance limiter kit that you can use to dial in the advance .Comes with springs, limiter and instructions. Works on a standard Mopar Electric dizzy. Lots of argueing about manifold vs ported. I've done them both ways and had good results . From the factory they were set up ported.I guess its a matter of what your trying to accomplish with it. If the car runs better with it on manifold it wont hurt it as long as your not getting detonation.