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Author Topic:   carburetor acting up
MDF99
Gearhead

Posts: 234
From: Hamilton, Ohio, USA
Registered: May 2001

posted 08-16-2002 05:11 PM     Click Here to See the Profile for MDF99   Click Here to Email MDF99     Edit/Delete Message   Reply w/Quote
I took the 650 double pumper off my 289 because it wouldn't cooperate, it refused to idle right (always rich) and at speed it would miss everynow and then and generally ran like $%*!!, it accelerated well, just while cruising along on a flat surface it would run lousy.

I put on a 750 w/ vacuum secondaries that I had laying around just for kicks. I bolted it down and fired it up, the rpms came right up to 3500 with the idle screw completely backed off and the choke wide open. What's up with that? Could the secondary idle screw be open to far? (the little set screw on the bottom of the throttle plate) I set it by twisting it in until the secondary plates just barely moved.

The 650 DP has 74/83 jetting w/ 4.5 powervalve.
The 750 Vac. has 72/78 jetting w/ 4.5 powervalve.

Any diagnosis would be greatly appreciated.

------------------
Matt Fraley
1966 Mustang Coupe; 289, T-5, 9" 3.50
http://mdf99.tripod.ca/289_Side.jpg

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SteveLaRiviere
Administrator

Posts: 45869
From: Saco, Maine
Registered: May 99

posted 08-16-2002 09:04 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
With the engine off, look down the throats and you'll probably see either the primary or secondary throttle plates hung open. Then you can trace what they are hanging on.

------------------
All Fords since 1977!

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steve'66
Gearhead

Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000

posted 08-16-2002 09:43 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Or the vacumm secondaries are flopping open at idle?!?

SteveW

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capri man
Gearhead

Posts: 7611
From: doerun, ga.
Registered: Nov 2000

posted 08-16-2002 10:03 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
what steve said!!

------------------
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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steve'66
Gearhead

Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000

posted 08-16-2002 10:40 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
LOL Mike

One of the Steves

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68F100
Gearhead

Posts: 2681
From: Burlington, Iowa
Registered: Oct 99

posted 08-16-2002 10:47 PM     Click Here to See the Profile for 68F100   Click Here to Email 68F100     Edit/Delete Message   Reply w/Quote
Does it jump up in rpms then die, or does it keep running? Reason I ask is that when I changed the carb on my truck, it would fire up, rev to uncomfortable (for me) rpms then die. I was pissed. Ended up being a bad gasket. I think it cost less than $2.

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MDF99
Gearhead

Posts: 234
From: Hamilton, Ohio, USA
Registered: May 2001

posted 08-17-2002 09:32 AM     Click Here to See the Profile for MDF99   Click Here to Email MDF99     Edit/Delete Message   Reply w/Quote
The RPMs come right up and it keeps on running.

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MattN
Journeyman

Posts: 69
From: Mattoon, IL.
Registered: Feb 2002

posted 08-17-2002 07:13 PM     Click Here to See the Profile for MattN   Click Here to Email MattN     Edit/Delete Message   Reply w/Quote
Look at the arm that opens the secondaries right above the baseplate, on the throttle shaft, right below the vacuum diaphram. It is probably hitting on the manifold. It might also need the gasket clearanced a little right there. This happened to a friend of mine. Hope this helps.

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stoker
Gearhead

Posts: 159
From: folsom,cal,
Registered: Jan 2002

posted 08-18-2002 08:23 PM     Click Here to See the Profile for stoker   Click Here to Email stoker     Edit/Delete Message   Reply w/Quote
is that original jetting on 650 dp?my 4777-2 650dp came with 67 & 76.how much hp with that 289?how high do you rev it?your jets seem a little big,i know this dont pertain to your problem (just curious)

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MDF99
Gearhead

Posts: 234
From: Hamilton, Ohio, USA
Registered: May 2001

posted 08-19-2002 01:34 PM     Click Here to See the Profile for MDF99   Click Here to Email MDF99     Edit/Delete Message   Reply w/Quote
My 289 has about 350 HP, perhaps a little more, it's still breaking in, but plan to rev it up to 6500. I agree the jets in the 650 sound too large. The carb. is from Bigs and they set it up, I got an email back from Bigs and they said to try jetting it down to 72/73 in the primaries and 77/78 in the secondaries. Hopefully that will help. How does that sound?

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stoker
Gearhead

Posts: 159
From: folsom,cal,
Registered: Jan 2002

posted 08-19-2002 07:36 PM     Click Here to See the Profile for stoker   Click Here to Email stoker     Edit/Delete Message   Reply w/Quote
that sounds so good ,ithink thats where i will start.should put me in ballpark,combo is 306 10to1 AFR 185s air gap,hooker super comps,2.5 mandrel bends all the way with x pipe

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MDF99
Gearhead

Posts: 234
From: Hamilton, Ohio, USA
Registered: May 2001

posted 08-20-2002 08:08 AM     Click Here to See the Profile for MDF99   Click Here to Email MDF99     Edit/Delete Message   Reply w/Quote
Stoker, you're combo is about the same as mine, I have the same heads, intake, headers, exhaust(H-pipe), I'm running 10.5:1 and a solid cam w/ 236/[email protected], .536/.545 lift, 108sep. So far this engine has been a learning experience and big fun.

------------------
Matt Fraley
1966 Mustang Coupe; 289, T-5, 9" 3.50
http://mdf99.tripod.ca/289_Side.jpg

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