Quote:

What I'm trying to figure out is if All the 1972 Distrbutors are all physically the same and maybe different internally(springs or weights) and if they all have same or different vac. adv. units (physically or internally). I have a 1972 400 4bbl auto and am Looking for an original Distributor. Do I need to buy one just for that application or can I buy a 2bbl or a 4spd one and make internal changes if they are different.



For the distributor to perform to spec, rather than just look correct, your odds are best if you can get hold one specifically for your '72 400 4 bbl auto. However, if you have access to a distributor tester, or are willing to spend some time testing on engine with a timing light, you can modify the internals to meet spec.

It will be hard to find the replacement springs by part number - although can try. Even more true for the top shaft-slot plate. So it comes down to tweaking what you have, taking parts from other applications or doner distributors and so forth. A standard, all mechanical vacuum advance will be not so hard as a pretty good range is still available new.

First thing to do is get a hold of a '72 shop book and write down the specs. Then look for all other applications with the same specs. A '72 parts book will reveal if the vacuum pod, springs etc were used for other applications that year. Then you can look at other years and if you post up, some of us can help by looking at other years.

In addition to the spring rate and advance slots (mechanical advance allowed), adjustments can be made to the initial spring force by turning the spring posts. The /6 folks know this, but everyone else seems to be unaware of it. On the secondary side this will change the point when the long loop engages.

Not many books on how dizzy's work. Some tech info here on the 'new' 1961 Chrysler built distributor
http://www.imperialclub.org/Repair/Lit/Master/136/index.htm