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FSB warrior
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Discussion Starter · #1 ·
I just got done tuning my mustang with a 74' 250 straight 6 in it. Keep these 2 things in mind. 1. its not the original engine and 2. there is no vacuum hose routing stickers on a 68 mustang. I noticed that there was a plugged vacuum hose on the carb. Then I noticed that it said "DIS" There was a vacuum hose to the distributor in one of those very top ports with the copper angle thing on the other end of it (when looking in the carb) I thought "that cant be right then" so capped the top carb port and plugged the hose (after some creative hose switching to get rid of one on the heater hose that I didnt need) It ran just fine, actually I think it ran better. However after looking on the distributor again I noticed something I have never heard of before. This dizzy has 2 vacuum lines attached to it, one going in the side of the vacuum advance and one in the front like normal vacuum advances. The normal one was hooked to normal manifold vacuum like it should, but now I was wondering if the other one has to go to the carb where it says DIS, which kinda looks like a timed source judging by the height on the carb or to the one it was originally hooked to??

Also what does it do so I can make the choice to just plug it??

edit: during this tuning I was able to get it to pull 18" at idle!!
 

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Hi Bronk, you have one of the 'famous' vacuum advance/retard distributors, which were a rudimentary form of polution control.

Now if I'm not mistaken, the "normal" VA port should go to a timed source on the carb, which will be near the throttle plate. The side VA port is the timing retard section, and should be connected to manifold vacuum. It retards the timing during decelleration, for emissions purposes.

You could try plugging it and see how it runs (probably will have no effect).

18"hg is super vacuum, must be an excellent engine.:beer
 

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FSB warrior
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Discussion Starter · #3 ·
Runnin'OnEmpty said:
Hi Bronk, you have one of the 'famous' vacuum advance/retard distributors, which were a rudimentary form of polution control.

Now if I'm not mistaken, the "normal" VA port should go to a timed source on the carb, which will be near the throttle plate. The side VA port is the timing retard section, and should be connected to manifold vacuum. It retards the timing during decelleration, for emissions purposes.

You could try plugging it and see how it runs (probably will have no effect).

18"hg is super vacuum, must be an excellent engine.:beer
Hot dang. Thats cool.

I always thought that "the normal port" went to a full vacuum source and the vacuum advance decided when to do the advancing. I am pretty sure the spot that said DIS is a timed source though.

And about the 18" it is amazing but no it is not an excellent engine, I have to spray starter fluid in it 2-3 times to get it to start when the engine is cold (even in the summer) Also its got about a 3/4" jump to it, so I think that just means ignition problem or small vacuum leak.

Ill get some pics uploaded of everything.
 

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FSB warrior
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Discussion Starter · #4 ·

where the top one and a port on the heater hose elbow was plugged into:

One says -GR and one says DIS. THe DIS was capped.
 

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FSB warrior
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Discussion Starter · #6 ·
the top carb port, the DIS and the top vacuum on the dizzy??
 

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FSB warrior
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Discussion Starter · #8 ·
1clean5.8 said:
top port on the carb and the secondary on the dizzy
Happen to remember what the DIS port was hooked up to??
 

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FSB warrior
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Discussion Starter · #10 ·
LOL thanks for all the info man:thumbup
 

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Bronkin' 'Round!
88 351/AOD/4” ProComp 94 351/E4OD/4” Superlift
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Points ignition, huh?

I have a whole duraspark setup for a straight 6 off my old 200 with a rather new set of plug wires, like 200 miles on them, that I could let go for pretty cheap. LMK if you want to upgrade.
 

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FSB warrior
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Discussion Starter · #12 ·

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FSB warrior
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Discussion Starter · #13 ·
just thought of something cool... when I get the engine in the only vacuum line Ill have is PCV:rockon (least untill I get power brakes that is.)
 

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FSB warrior
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Discussion Starter · #14 ·
I asked a guy I work with who was a mechanic and he said and found these pics that I could loosely go off of. That is assuming that the ports are used to both advance and retard the timing, and the advance doesnt have a spring to retard it back, then it is very important to have them both hooked up, but he said that It was pretty obvious it wasnt hooked to to the right carb vacuum though.


If you look real hard at the difference between the SCJ and the regular, you can see there actually isnt a difference between where the vacuum comes from

from the looks of this pic the carb vacuum they are talking about is ported


Im gonna see if I saved my buddies distributor from his 77, I may be able to use the vacuum advance of of it if I still have it.
 

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Not trying to turn you away from this great site, but a real good site for straight 6's is www.fordsix.com.

Those guys know about anything and everything you could ever want to know about these little engines. I am running a 250 in my '72 Maverick. I have the Duraspark II setup and the DIS has a line going from it straight to the vaccume advance on the distributor. The other port is for a EGR valve on later model cars and you can just plug it. With an old points distributor, run a vaccume line from the DIS port on the carb straight to the end of the vaccume advance. Then plug the port on the side of the vaccum advance. This was the way that my car was when I got it and it ran fine.
 

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FSB warrior
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Discussion Starter · #17 ·
78 Bronco XLT said:
Not trying to turn you away from this great site,
Thanks for the info, its very helpful. Also I dont even own a bronco anymore, but im not going anywhere!
 
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