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Author
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Topic: Power Valve
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Glens67
Gearhead Posts: 325
From: Petaluma
Registered: Mar 2002
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posted 07-25-2002 05:24 PM
   
Hey just thought of something else. What power valve should I be using if I only have 6" vacuum at idle? There is a 6.5 in it now Fuel pressure still dropping off to 4.5 psi even after installing a new mechanical pump with the holly red pushing. Going to pull the sending unit check the fuel line replace all of the soft hose.
Glen
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steve'66
Gearhead Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 07-25-2002 07:56 PM
Glen,That power valve is opening at idle, it must be a PITA to adjust the idle mix. A 3.5 power valve would help, but it's not the problem downtrack. Even the 4.5#s of fuel pressure should keep the carb's bowls supplied.
I'm suspicious of the low vacumm, that's just not right. 
I hope someone on this comes up with the solution. Good luck  SteveW Here is the original post about this problem
https://mustangsandmore.com/ubb/Forum12/HTML/003106.html
What would cause low idle vacumm? Tight valves, cam too far advanced, vac leak (not in this case). That cam should give 12+ inches of vac at idle. IDEAS? Come on guys, we're the best.  [This message has been edited by steve'66 (edited 07-25-2002).]
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Glens67
Gearhead Posts: 325
From: Petaluma
Registered: Mar 2002
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posted 07-26-2002 01:27 AM
While checking the fuel delivery problems. I used the electric pump to empty the fuel tank. As luck would have it I used a piece of clear hose, I saw what looked like air bubbles traveling in the gas stream at the pump discharge. They dissappeared before they got to the end of the hose, and there were no bubbles in the container. I popped the gas cap on the Mustang's tank and found that I had pulled a vacuum on the tank. Is a 67 mustang suposed to have a vented tank? I keep finding more small things on the fuel system. What is the best way to vent the tank?
One friend (Dave 460 mustang white FB) said that he collapsed his tank with a Holly Blue pump. he soldered a tube fitting on the filler neck and used a PCV valve and a short hose.
Glen
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speedy
Gearhead Posts: 186
From: Parkersburg WV
Registered: Nov 99
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posted 07-26-2002 01:48 AM
Use a power valve rated 1 to 2 inches below idle vacuum. Auto trans., take the vacuum reading with the trans. in drive.Andy
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68 S-code GT
Gearhead Posts: 1044
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 07-26-2002 07:21 AM
I?ve used the red and the blue pumps in the past and never had a problem with the tank collapsing or having enough fuel being pushed through. I only had problems with the magnets in the pump motor coming lose! You might have some kind of blockage. Have you checked the pressure at different points in the fuel line?
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steve'66
Gearhead Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 07-27-2002 12:11 AM
ttt,Someone's gotta know what could cause low idle vacumm, besides a vac leak.  SteveW
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Larry Jennings
Gearhead Posts: 540
From: Redwood City, Ca. USA
Registered: Apr 2000
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posted 07-27-2002 12:15 AM
How sure is the timing mark?------------------
I'm desperately trying to figure out why kamikaze pilots wore
helmets.
- Dave Edison
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Glens67
Gearhead Posts: 325
From: Petaluma
Registered: Mar 2002
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posted 07-27-2002 08:50 AM
0 right on when degreed in and TDC #1 checked.------------------
Glen
67 GT 390
65 Galaxie 500 XL 4 Speed
It was not a Red Light they gave me a Slow Tree
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Larry Jennings
Gearhead Posts: 540
From: Redwood City, Ca. USA
Registered: Apr 2000
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posted 07-28-2002 01:07 PM
Have you locked the dist, or does it still have a curve in it?------------------
Advertising is the science of arresting the human intelligence long enough to get money from it. Stephen Leacock
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Glens67
Gearhead Posts: 325
From: Petaluma
Registered: Mar 2002
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posted 07-28-2002 02:11 PM
Mallory Unilite All in at 3000. 12 inital 26 in the dist. 38 total
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Larry Jennings
Gearhead Posts: 540
From: Redwood City, Ca. USA
Registered: Apr 2000
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posted 07-28-2002 04:31 PM
Just for giggles dial it up to 38 at idle for a second and check the vacuum to see how happy it would be if it were locked. If you do lock it you can still drive it on the street, just don't pull a trailer with it . ------------------
Advertising is the science of arresting the human intelligence long enough to get money from it. Stephen Leacock
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