I have a msd 6al and pro-billet #85551. Can anyone tell me when the timing will start to advance. Not sure if thats all the info needed.Thanks

Is this an "out of the box" part? If so, I believe they put the medium springs in from the factory and it will be at full advance by 3000 or so. Not sure when it starts to advance, probably by 2000.

MSD should be able to tell you. There are instructions that come with the distributors that also tell you, they may be available on thier web site.

Bill gave you the best advice to find out but a ball park guess would be around 900 rpm knowing most engines idle below that...

It was a new distributor that I got from a friend(with no directions). I guess I'd have to look at the springs and give msd a call.

Since it's used, who knows whats been done to it... You can always spend a few minutes to install it and test it... After installing it, set the idle down as low as you can get it and check the timing with the vacuum advance plugged off if it has VA. Check the timing and rpm. now bring it up 100 rpm at a time and check the timing each time. The first time the timing goes up drop the idle by 50 rpm and check again. You get the idea...