2 vacuum port distributor question ?
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2 vacuum port distributor question ?
My 71 360 2bl has two vacuum ports on the distributor. Does one advance and one retard timing? One to ported vacuum on carb and one to manifold vacuum or what?
Thanks for your help!
Thanks for your help!
Posting Guru
Joined: Aug 2002
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From: Minneapolis, MN
2 vacuum port distributor question ?
If it's like the dual diaphragm advance on my '71 429 the front (advance) chamber goes to ported vacuum and the rear (retard) chamber runs through a TVS to manifold vacuum.
Post Fiend
Joined: Feb 2000
Posts: 5,130
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From: Brea CA
2 vacuum port distributor question ?
Yep, they are all the same.
The retard only works when the advance is in the rest position, in other words the retard is the soft stop for the advance and retards it from that point. The two don't fight one another.
Barry
The retard only works when the advance is in the rest position, in other words the retard is the soft stop for the advance and retards it from that point. The two don't fight one another.
Barry
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2 vacuum port distributor question ?
Is rear (retard) the port nearest the dist? No TVS on mine. I have front dist. port to carb and rear port directly to manifold tree? My suspect my vacuum advance (front port) may not be working right. Should the distributor plate rotate when I suck on the vacuum line or if I try to rotate it by hand? Mine won't move and seems to be frozen solid?
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2 vacuum port distributor question ?
I found out why the advance would not work. The previous owner stuffed three washers in behind the spring. Took these out and the vacuum advance works. The retard port (nearest the dizzy) holds no vacuum at all. I can suck or blow air straight through it but when I attach the mabifold vacuum line the idle drops some. Is this normal?
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2 vacuum port distributor question ?
I'm thinking I should buy a new vacuum advance unit. Should I stay with the dual port type or just get the single (advance port) type? I believe the one I have is adjustable with a large nut where the previous owner stuffed all the washers in. All the new ones I can find do not have this nut for adjustment ???
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Post Fiend
Joined: Feb 2000
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From: Brea CA
2 vacuum port distributor question ?
Some of the new ones are still adjustable but not like yours where you can stuff washers inside. Instead, inside the advance nipple is an adjuster that you stick in an allen wrench thru to tighten or loosen the spring tension.
Barry
Barry
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2 vacuum port distributor question ?
I took the washers out so it will advance when I suck on it but when I put it back together it runs like crap. With the carb vacuum line attached to the advance port no change at idle but starting at about 1000 plus rpm the engine shakes violently and started smoking out the tail pipe (that's a new one...) If I pull it off, cap it and just run manifold vacuum to the retard port it runs great and does not smoke..?
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2 vacuum port distributor question ?
btw... Dizzy vacuum advance does not leak. It will hold a vacuum when I suck on it. Unlike the rear (retard) port that leaks like a sieve, sucking or blowing..?
also... Carb vacuum reading is 17-18 max at 1,000 plus rpm. Manifold vac develops 18-19 at idle.
also... Carb vacuum reading is 17-18 max at 1,000 plus rpm. Manifold vac develops 18-19 at idle.
Posting Guru
Joined: Aug 2002
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From: Minneapolis, MN
2 vacuum port distributor question ?
Hook up a dwell meter to see if the dwell is changing drastically when it's advancing. Could be a worn pivot on your breaker plate and with the increased advance your points gap is changing.
Post Fiend
Joined: Feb 2000
Posts: 5,130
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From: Brea CA
2 vacuum port distributor question ?
That's a good point.
Even when these Ford dizzys work perfectly, the dwell changes a little with the vacuum advance 'cause the breaker plate pivot is not concentric with the breaker cam, cheezy design.
Another thing to check is that the ground strap from the breaker plate to the housing is intact.
It sounds like you're getting too much vacuum advance.
Barry
Even when these Ford dizzys work perfectly, the dwell changes a little with the vacuum advance 'cause the breaker plate pivot is not concentric with the breaker cam, cheezy design.
Another thing to check is that the ground strap from the breaker plate to the housing is intact.
It sounds like you're getting too much vacuum advance.
Barry
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