How to tell if they're bad. Well, if it advances too much or too soon. Asking whats too much or too soon, is tougher to answer. Does it ping alot? If yes, then try backing off the timing a few degrees and seeing if it goes away. If that solves it, and car drives okay then go with it.
Also, the spring posts can be shifted (some models may only have one post that rotates, may depend on the vintage also), and I've done this to counter the old springs.
But back to too much advance. To see how much max advance the springs were allowing I used a vacuum pump w/gauge hooked up to the dist diaphram- first with the car not running, so I could see how much pressure it took to rotate the dist plate to it's limit, I used the pump to apply vacuum. Then did the same with the car running. Applied the same amount of vacuum and used a timing light with advance degree knob to see how much advance the max vacuum would apply. In my case the max advance was 30 degrees. Haven't gotten an answer on whether thats too much or too little. From searching in the db it sounds like thats ballpark.
New spring source:
Only new ones that I've found are the Mr. Gasket springs part # 925D.
Advance Auto doesn't stock them but their online store, really a different outfit, does sell them: partsamerica.com.
I'm pretty sure summitracing.com has them as well.
But you can check your local parts stores and see if they have them.
Other than the Mr. Gasket part I think the only source is from junkyard.
matt
PS: Some of the springs for the HEI distributors may work - but they are slightly different, and typically those kits include a variety of springs which make them 2x or 3x the price of the Mr. Gasket 925D kit.
