Vacuum advance

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Re: Vacuum advance

Postby whiteblur on Sat Jun 18, 2011 12:12 am

forrestbump wrote:My guess is your vacuum advance line is connected to the ported vacuum tube, I've followed Woods' advice and connected mine to the direct port, readjusted my carb and admit it's running much better.


mine is connected to the vacuum advance line and yours is to the direct port :? not understanding
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Re: Vacuum advance

Postby forrestbump on Sat Jun 18, 2011 12:20 am

There are usually two vacuum ports (metal tubes) in the front of carbs.  The higher port (tube) is called a timed port as it is affected by butterfly movement.  The lower port (tube) is a direct source of vacuum and is NOT affected by butterfly movement.

Most carb suppliers recommend using the timed port, but after reading Woods' (he's a very knowledgeable member here) posts in the "Mileage Quest" thread found in General Discussion, I've changed my thinking and now recommend using the direct port location as the proper source for vacuum advance canisters.
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Re: Vacuum advance

Postby tmcalavy on Sat Jun 18, 2011 7:01 am

I think a picture is worth a thousand words in this situation...don't have an I-6 anymore, so can someone post one showing him the vacuum line routing? He is unfamiliar with our/your terminology.
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Re: Vacuum advance

Postby woods on Sat Jun 18, 2011 10:44 am

It may be a bad vac can like mentioned above. It may also be pulling in too much timing OR if the plate your points sit on is worn out, the vac advance can pull it at an odd angle which can change your point gap. Fix the vac leak and fix whatever is going on with your distributor. Running "fine" is really up to personal interpretation. With a vac leak and no vac advance...I can tell you without even driving it, that I personally would not think it ran fine. In other words, if you think it runs good now, you will be amazed at how it can run when everything is correct.
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Re: Vacuum advance

Postby Whateverman on Sat Jun 18, 2011 11:32 am

it may run "fine" idling in the driveway and revving it up with the vac advance off, but it'll end up pinging and knocking its way up the road ,especially if you run into any hills- not to mention backfiring ,stumbling and stalling
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Re: Vacuum advance

Postby fordman on Sat Jun 18, 2011 11:47 am

there is some thermactor type of vaccum routing on this page. that may help. http://www.fordification.com/tech/schematics_e.htm
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Re: Vacuum advance

Postby whiteblur on Sat Jun 18, 2011 3:27 pm

i checked the vacuum can and it all seems to be good. I took it for a drive around the neighbor hood with the other port open and the vacuum advanced hooked up and it stumbles and the exhuast pops and when you slow down or push in the clutch if you dont give it gas, it'll die
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Re: Vacuum advance

Postby woods on Sat Jun 18, 2011 4:31 pm

First...no vacuum port should be uncapped.

Now take your distributor cap off and slide the plate your points sit on toward the way the canister pulls it. Is it loose? Does your point Gap change from one position to the nest even though they are on the high spot of the cam?
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Re: Vacuum advance

Postby tmcalavy on Sat Jun 18, 2011 9:24 pm

Unless I missed something...wish we knew which carb you have so someone can tell you how may vacuum hookups you have and which ones should be capped and which one connects to the distributor. Until then, who can say?
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Re: Vacuum advance

Postby whiteblur on Sat Jun 18, 2011 10:58 pm

Carter yf manual choke
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Re: Vacuum advance

Postby tmcalavy on Sun Jun 19, 2011 8:54 am

Try this on for size:
http://oldcarmanualproject.com/manuals/ ... /index.htm
It's been too many years for me to remember the exact YF vacuum routing.
If the link above doesn't help do a Google search for Carter YF manual choke vacuum diagram and see what you get.
You may have a PCV vacuum connection on the manifold under the carb, and for sure one vac port on the carb that goes to your distributor...but can't remember where you attach the power-brake booster vac line on your setup. Hang in there, you're getting closer.
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Re: Vacuum advance

Postby happycamper on Mon Jun 20, 2011 11:37 pm

vacuum advance is supposed to go to a "timed" vacuum port; not a full-time/full manifold vacuum port. If it is hooked to full manifold vacuum, you will be running "advanced" all the time. Just went through this with Holley tech support. My  :2cents:
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Re: Vacuum advance

Postby woods on Mon Jun 20, 2011 11:54 pm

Holley tech is wrong (just so you know). I don't want to go through all this over again. Please read this.
http://www.fordification.com/forum/view ... &start=120
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Re: Vacuum advance

Postby Fo-Mo-Co on Tue Jun 21, 2011 7:54 am

woods wrote:Holley tech is wrong (just so you know). I don't want to go through all this over again. Please read this.
http://www.fordification.com/forum/view ... &start=120


I second this.  I won't go into all the BS I have gon through but Woods is correct Holley is wrong.
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Re: Vacuum advance

Postby tmcalavy on Thu Jun 23, 2011 5:06 pm

I followed woods' link to the other thread and got caught up there with my reading...went out after work today and hooked my dist. up to manifold vacuum on the rear of the 360 in my 69 F250...there's a splitter there. Also plugged the port on the carb that I was using, and really like the engine response now. Like he says, it wakes your engine up. I'll know in a week or so if it makes a difference in mpg...I'm getting 12.7 in town driving right now.
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