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  Man, my carb has me crying....

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Author Topic:   Man, my carb has me crying....
Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-08-2002 09:23 PM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
Got a Holley 4777 700 DP on my 351C. Fresh rebuild.

66/76 jets, second new 6.5 power valve, 13 inches of vac at idle.

This darn thing will bring a tear to even the hardest man's eye at an idle. Been that way for a long time, through many power valve changes and idle adjustments.

Please give me some ideas, man everytime I go drive the car I come back stinking like I've been working in the shop all day.

Plugs look tan to white, although a little black soot is evident on the threads.

Thanks for any and all ideas,

Greg

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'71 Torino GT w/ 351C, soon to be 466/C6.

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capri man
Gearhead

Posts: 1716
From: doerun, ga.
Registered: Nov 2000

posted 08-08-2002 09:39 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
check float levels and for trash in needle and seat and get back to us.

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mike r
racing is real
everything else is just a game.
81 capri-7.51 @89mph 1/8
1.54 60 ft.
http://prestage.com/site/site_display.asp?SiteID=141

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jsracingbbf
Gearhead

Posts: 261
From: Batesville,MS. , U.S.A.
Registered: Mar 2002

posted 08-08-2002 09:42 PM     Click Here to See the Profile for jsracingbbf   Click Here to Email jsracingbbf     Edit/Delete Message   Reply w/Quote
Greg, make sure the air bleeds aren't stopped up or restricted.

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Jerry Smith
69 Mustang Pro ET Drag
"Even a blind hog can find an acorn every now and then "

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steve'66
Gearhead

Posts: 4337
From: Sonoma,CA,USA
Registered: Mar 2000

posted 08-08-2002 10:09 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Greg,

How high is your fuel pressure? Fuel is getting by your float's needle valves causing high fuel levels in the bowls. High fuel level makes for a rich mix, and watery eyes.

SteveW

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Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-08-2002 10:40 PM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
Thanks for the quick replies, guys!

I have not checked the float levels recently, I'll do that next.

As far as I can tell, airbleeds are open. When I had the carb apart last I verified both primary and secondary airbleeds were open. One was clogged, and siphoning fuel out of the bowl. I used carb cleaner and a small wire to be sure and clean all of the crud out.

Fuel pressure is an unknown, since my Holley pump took a dump a couple of months ago. It was 4-6 psi with that pump, now I have a stock replacement carter mechanical. Symptoms remained the same with either pump.

I'll re-post after I check the float levels.

Thanks,

Greg

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'71 Torino GT w/ 351C, soon to be 466/C6.

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Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-09-2002 11:04 AM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
Well, I just checked the float levels, both primary and secondary have a fuel level about 1/8" below the sight hole. Seems OK to me.

Any other suggestions or ideas? This is a real problem.

Thanks,

Greg

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'71 Torino GT w/ 351C, soon to be 466/C6.

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Moneymaker
Administrator

Posts: 13229
From: Lyons, IL, USA
Registered: May 99

posted 08-09-2002 11:24 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Try a 4.5 power valve. That will lean it out at part throttle and idle only.

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

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Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-09-2002 09:13 PM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
Alex, I had the same Idea. I tried a 3.5 and a 4.5, and the only thing that changed was I got a lean bog from part throttle acceleration.

I'm getting ready to toss this carb in the trash.......

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'71 Torino GT w/ 351C, soon to be 466/C6.

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Rustang
Gearhead

Posts: 279
From: Dubois PA
Registered: Nov 2000

posted 08-10-2002 08:06 AM     Click Here to See the Profile for Rustang   Click Here to Email Rustang     Edit/Delete Message   Reply w/Quote
Maybe your primaries opened too far into the transfer slot at idle? Adjust your secondary idling open a little more so you can close the primary idle down more. This might allow you to tune out your rich idle condition better with the idle mixture screws.

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'68 mustang 351 clevor- [email protected]
'67 Stang, 351W [email protected]
'69 351C [email protected]
'78 Pickup [email protected]
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Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-10-2002 04:49 PM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
Good call, Rustang, I checked this out yesterday, and here's what I found.

I already had opened the secondaries somewhat to allow a normal primary idle setting. The throttle plates are almost all the way closed in the primaries and give an 800 RPM idle in neutral.

The idle mixture screws are about 2 turns out each. Any leaner and it surges at idle and dies, any righer and it idles smoother but really gets to stinkin'.

What else could I try to diagnose this condition?

Thanks,

Greg

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'71 Torino GT w/ 351C, soon to be 466/C6.

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Rustang
Gearhead

Posts: 279
From: Dubois PA
Registered: Nov 2000

posted 08-10-2002 09:22 PM     Click Here to See the Profile for Rustang   Click Here to Email Rustang     Edit/Delete Message   Reply w/Quote
A couple other things. Vacuum leaks seem to cause crazy, untunable idling. Also, what is your timing at idle? Do you run vacuum advance? If so, I'd run ported vacuum off the front metering plate. That way you're not getting so much advance at idle. Have you looked down in your venturi's to see if you're pulling fuel thru the boosters at idle? That might be a sign of plugged air bleeds.

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Greg Pettit
Journeyman

Posts: 45
From: Dallas, TX
Registered: Nov 2001

posted 08-11-2002 11:11 AM     Click Here to See the Profile for Greg Pettit   Click Here to Email Greg Pettit     Edit/Delete Message   Reply w/Quote
I am running vacuum advance, off the metering plate, no vac there at idle. I have a stock duraspark distributor using the 13 reluctor slot reduced to approx 10 with a rubber bushing, light springs.

Vac advance is a 10 degree unit the best I can tell.

My balancer has slipped on the hub, so accurate timing is a guess. I set it up to just be below preignition on 87 octane gas. Wouldn't think this is too far advanced, but hey who can tell with my crappy balancer!

I'll check the boosters and for vac leaks today and get back to you.


Greg

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'71 Torino GT w/ 351C, soon to be 466/C6.

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