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Hi All, I have this seemingly original Dual Vacuum Distributor (pictured on my '69 F100 with a 302. Anyone know how to adjust the amount of advance and retard? There is no small allen wrench slot in the hole and no obviously springs under the cap. Secondly, any reason why I can't just plug the retard and only run advance off direct vacuum (it runs through that crazy vacuum tree thing right now)? I think the retard was probably some fuel saving something-or-other.
I used to change the advance line directly to the ported section of the carb instead of where Ford put it, then remove the rear hose completely. Then after setting the timing by ear, it made a big difference in power.
That's good to know! I am rebuilding the carb so I'll try that once it's back on. But is there any way to tamper with how much advance if I want to dial that in as well? I've been able to do that on other vacuum advances and just can't figure this one out.
No, I think you are correct. I don’t believe that every Ford vacuum canister was equipped with an adjuster. Some certainly were, but I’ve seen plenty that didn’t have one.
Or at least I couldn’t see it.
There is a thought out there to leave the rear port open, or at least vented perhaps through a tube to keep debris and moisture from getting in. But some feel that capping it could restrict movement of the diaphragm.
So I’ve always left mine open.
That said however, I have never actually tested that theory. Would be pretty easy to do though by simply hooking up a timing light and watching what happens when the rear port is left completely open versus completely closed.
Seems like there would be enough air volume left inside to allow the diaphragm a full range of movement, but I just don’t know.
The mechanical advance is “adjustable“ but unlike GM distributors that have the flyweights and springs and plates on top, ours are under the points plate.
If you further disassemble the distributor you can see the weights, the springs, and the advance slots.
You can find different plates with longer or shorter slots to limit the total mechanical advance. You can also find different weights and springs to adjust the rate of advance.
I just had a new distributor re-curved by the "Distributor Man" on this site, base timing 12-16 degrees, I like 12, Full mechanical advance all in at 2250 rpm & 34 degrees. Can't remember what vacuum canister allen was set at, sorry.
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