Just to clarify the adjustment will have to be made to the mechanical advance in side the distributer.
SLK, from what you and your mechanic came up with it sounds like your distributor is introducing an additional 40-42 degrees of timing. Some distributors have bushings that can be changed to limit the amount of advance that's introduced. Others like Mallory's have adjustable arms in them and it can be varied. I'm not sure what style you have, but it seems like your distributor is adding way to much mechanical advance. If this was checked without the vacuum canister hooked up, then when you couple the mechanical with the vacuum advance it really must be giving it a ton! I do have a question though, how did your mechanic check for total advance? Did he have a dial back timing light, because I would guess that your damper isn't marked at 60*. Either way, you need to get the timing working correctly first. Like everyone says, just make one change at a time and see how things are effected.
I went back today and he could not get to it I will have him tell me where it's at with the vacumm removed then adjust accordingly.
