Good to know. Mallory used to make a module that advanced (Mallory # 9-29800). It's what came in my Mallory distributor I picked up for $100 closeout when MSD bought Mallory and discontinued them. Now they are NLA; I mention them because there might still be some floating on ebay.

I've since verified the stock GM distributor has the screened vents standard - Merc did nothing to them to maranize them. SO you could get a rebuilt GM dist (~$80) and a Delco D1965A (~$70) and for $150 have a marine HEI with built in 22-24* curve.

A good friend lost spark on his 1999 502 mag and it ended up being the distributor. This distributor was the exact same as the factory unit for $100.

That's (even though a Cardone reman) the Delco / Merc EST, Voyager we are referencing.

Here's the one from Delco themselves:
http://www.amazon.com/gp/offer-listing/B001S34JP0
Note: supposedly comes with cap, rotor too.

You can see the screened vent (flame arrestor) on the left side of the cap base:

you are mistaken. Merc put their shiny black paint on them. that way they can charge 3 times as much...

They where being nice......compared to if they sprayed it with their blue paint.

LOL. So true...

while we are on these dist, had a issue few years ago on a 87 SS monte carlo, started running bad, seemed like a carb issue, had the electronic Q-Jet apart several times, could not figure it out...then GM tech told me to replace the dist shaft..I was ???? but yeap was the issue !!!! last year had a friend with 90's 1500 truck, kept stalling, he changed everything...no luck...had him change shaft again that was it, so just info on a weird issue with these, they loose their magnitism and will not work right..