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Since I've got the bug down I thought I'd try modifying a pertronix SVDA canister to be able to also boost retard. I've had it apart before to change the sensitivity of the vacuum advance so I figured it should be easy.

I just separated the base from the canister, slipped in a bit of spring, and tested it with a pressure gauge. I'm getting full actuation of the arm at 6psi. No idea how much actual retard this is going to equate to but it's easily better than a locked out or limited distributor. Here are a couple pics:

Hah! It adds as much as ten degrees with a strong vacuum and retards 8! I'll set my max at 28* and I'm all set. :thumsup:

Perfect! I used a vacuum can from a saab dizzy on my amr500 build I never did measure the amount of retard though.lol

I'm probably getting more retard than I need early on, but better more than not enough. I know I'll be about where I need it at 10psi at least. Right at 20 degrees.