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Vacuum Advance Canister Diaphragm Ruptured... twice

Jimmmmmay

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Hey everyone. I've got a Proform 66990 distributor in my 408 stroker motor that I bought new back in November from Summit Racing. Back in April, I noticed the vacuum advance canister wasn't holding vacuum anymore. I called up Summit and they worked with Proform to send me a new canister (really happy with their customer service on this, btw). Got the new one and put it on, set the timing, etc. It was working great for about 100 miles, but it ruptured again. I wasn't beating on the car hard or anything and I'm going to contact them again about sending me out another canister, but what do you guys think? Has anyone heard of this happening so frequently? I'd like to think it's a fluke and just a part quality issue, but having it happen twice in such a short period of time makes me wonder.

Thanks,

Jim
 

Chryco Psycho

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Is it adustable if you insert an allen wrench into the port where the vacuum hose attaches ?
Personally I never use vacuum advance , I dial the vacuum off so it cannot move & tailer the mechanical curve only , usually 14-20 initial & total timing around 34-38*
 

halifaxhop

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Lots of people assume it adjusts the amount of vacuum advance, what it does is adjust when the vacuum will bring it in full (number on the arm)
 

Chryco Psycho

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The Allen screw ??
No if you bac the allen screw counterclockwise all the way out the vacuum advance will not move , the # on the arm is the max amount of advance it can add
 

Jimmmmmay

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I wound up buying a NOS Napa Echlin vacuum advance canister and threw it on there. I'm a sucker for made in 'merica parts. So far so good. I've been out a few times like normal and haven't had an issue yet. All of my canisters have been adjustable, too. I did mess with them and set it to get the vacuum adv in as early as possible (turned the screw clockwise). The interesting part is that I took both of the broken ones apart and it looks like the diaphragm didn't tear, but the outside edge of it pulled out of where it's crimped in the metal fold. Who knows. Hopefully this Napa one holds up better.
 
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