68 dual port vacuum advance
 

Hey guys,
Thanks to everyone for the responses to my search for an idle stop solenoid for my 68. Another question, when I bought this girl, they had put a single port vacuum advance onto the original distributor. I was able to source a dual port vacuum advance/ retard elsewhere, but I believe it is off other equipment. It screws in perfectly, but does anyone know if the dual port 68 vacuum advance works with any plug in dual port, or is specific to the 68 Pontiac. I would like to fire her up the first time after the rebuild with as few variables as possible. And if it is specific, does anyone know where to find one.
Thanks,
Jeff

They come up on ebay from time to time.

Unless you're building a show car, using the vacuum advance system from 1968 isn't the most efficient way to tune the car. If you understand how it works, it can be modified to look stock but work much better to provide the advance curve your engine needs. But once you install it, block the retard function and adjust the advance to cope with todays fuel.

A complete description of how this works is in the 68 Diagnostic manual

Jeff, Pontiac released a TSB in late 68 instructing dealers to disable the retard function on the dual port vacuum cans.

You could still use one, run the hoses but do something like put a BB in the retard line to disable it. Lots of discussion on this topic in the 68 GTO section.

I'm guessing your distributor is stamped 1111270 which calls for a 1973412 vacuum control. The manual trans version (1973411) has a 20 degree advance and 10 degree retard as in this NOS one for sale on Ebay:

http://www.ebay.com/itm/314412325845...OPIC%26ao%3D1%

Another (used) 1968 vacuum control on Ebay (for big Pontiacs) is also 20 degree advance which would be a good bet that all 1968 Pontiacs with the dual port vc requires 20 degree advance?

If so, then your "other equipment" dual port vc should work fine if stamped 20A...just disconnect the retard port.

Hi 6D7,
The 1111270 is correct on the distributor. Not sure exactly what the dual port is off, but an 03, with a slight curvature continuing up and to the left of the 0. The zero may actually be an O. Purchased it off eBay as well, but I don’t see a 20 marking on it. The marking I see is in black, directly above the lower port. Should I be looking somewhere else?
Thanks,
Jeff

Hi Jeff.

Tried to private message you but it says my box is full.

Anyway, I used to have leftover distributor parts. Will look in my stash for a correct 412 with the advance port working (holding vacuum). If so, you can have it for free. Otherwise, like OG68 said...they come up on Ebay once in awhile...which may be the your best plan of action rather than messing with the one you have.

Robert
6d7gto@gmail.com

Hi Robert,
Thank you very much.
Have a nice weekend,
Jeff

Hi Jeff.

Don't have any 412 controls but have a 367 which was used on 1967 A.IR. (smog pump) engines. Same advance and retard 20A 10R. Not sure if the advance on both controls open at the same rate of speed? Maybe someone can chime in that knows distributors and how the vacuum control affects function?

Retard port does not hold vacuum on this 367 but you would plug that port anyway.

Since it won't cost you anything, you might want to give this a try. Most likely, it would work better than the unknown control you have now. Please email me. My message box is full.

Robert
6d7gto@gmail.com

I have 2 working factory original dual ports for a 68. One is on my distributor but I don’t use the retard port. I’d be willing to let my spare go.


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vacuum advance
 

Interested in the dual port vacuum advance. what are you asking for it?

Ed

Hi Ed. I think I paid over $100 for it a few years ago. Are you also on gtoforums? think we’ve corresponded many times there. If I remember correctly you have a spare optical line for the ashtray (68).


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Having owned a few 68s this is what I do

It’s still on the original distributor. I did a vacuumed test and it holds. It’s it remarkable shape.

https://uploads.tapatalk-cdn.com/202...de2f653eff.jpg

https://uploads.tapatalk-cdn.com/202...8afd3092d8.jpg
https://uploads.tapatalk-cdn.com/202...d283632005.jpg


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