pretty good writeup. You haven't gotten into the speed of the curve yet.
Thanks and you are right, I didn't mention the speed of the curve yet but was hoping someone would bring it up. :) The heavier of the two springs now does nothing because the movement of the weights is restricted below the point where heavier spring with the larger "eye" would take effect. With that being said, the smaller spring is the only one that does anything and this is good. Advance starts at 1400 rpm and progressively increases until 2500 rpm. It's perfect for my application but MP offers a spring kit for their dizzys if a different curve is required.
I've only worked with the small block distributors with the stock advance mechanism. I will make a few suggestions, some of which are only relevant to the factory style advance mechanism.
First thing is that I never worry to drive out the roll pin first. Its used like a keyway on on the shaft, which fits in a slot underneath the step. Therefore, its fit on the shaft is not an issue if you lift it up. I use two large screwdrivers and pry straight up without disturbing the pickup. You pry from both sides evenly and its easy. That alone will save you time.
Yep, the MP is different in that it doesn't use a horseshoe clip to hold the reluctor down like a stock dizzy. A couple of taps with a light ball peen to drive the pin down helps to reduce the force needed to remove the reluctor and prevent galling of the MP's brass shaft. I did mention the screwdriver method. :)
Then, i pull the advance mechanism out by removing the two screws then separating the pickup plate a bit until it comes out. easy. next thing is to take the other screws out and remove the mounting plate.
Yes, MP and stock dizzy's are identical in regards to getting the advance arm out.
The length of the slot determines the total advance. So on the MP distributor if you know the length of the slot and the distributor degrees that it did before (as a result of your dial back light), you can create a ratio for what you have and what you're looking for and cross multiply. On the stock distributor you have to subtract the diameter of the pins before you make your ratio. On the stock distributor, you have to weld and file it to the right length...still not bad.
Here is where the MP and stock style differ. The advance mechanism is entirely different and no slots are used on the weights. I have some photos of a stock dizzy build but the springs were too light for my application and advance came in way too soon (800 rpm). I too welded up the slots but used the degree wheel method for verification when it was completed. I'll post up that build at a later date. 8)
I've found you want to have total timing come in by 2400rpm and start around 1100-1200rpm. On my distributor I have ONE light spring with a coil removed. Now she runs great...15 inital and 35 total without the vacuum can hooked up.
