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Author
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Topic: Getting the Idle down!
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68 S-code GT
Gearhead Posts: 2416
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 07-08-2002 07:40 AM
   
Looking for some ideas of what to do! It��s a stock 66-289 with an iron 68-4V intake along with a 69-600cfm 4300 carb on top and headers. I think its idling around 1200-1300 because my Tack/Dwell meter stops at 1200 and the needle is fluctuating. I can��t get it down any further, is there something not installed correctly on the carb or an adjustment I��m missing? I thought it might be the fast idle adjustment but I have the screw backed off all the way along with the primary idle adjustment! The timing is set at about 6 deg. for now.------------------
68 S-code FB GT 4spd(now C6)/3.25 PS PDB
68 J-code(now 289) Cp Sprint"B" C4/3L00-9" PDB PS AC
99 F150 XLT Ext/cab, 4X4, 5.4L, 3L55
95 Explorer XLT with the works! (Wife��s car)
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Jeff
Gearhead Posts: 306
From: Moore, OK USA
Registered: Mar 2001
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posted 07-08-2002 03:24 PM
quote:
Originally posted by Jeff:
My guess is the linkage is hung up on the side of the intake manifold. With some carbs on some manifolds, the right side of the linkage does not clear the manifold and hence does not allow the primary butterflies to fully close. Try loosing the carb bolts and pushing the carb hard towards the passenger side. This small extra clearance often frees the bound linkage. Use a carb spacer if this doesn't free the linkage.
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SteveLaRiviere
Administrator Posts: 42859
From: Saco, Maine
Registered: May 99
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posted 07-08-2002 07:25 PM
Things to check:*Weak return spring. Try moving the throttle closed as see if that slows idle. *Vacuum leak. Can you stall the engine by blocking the choke housing with your hand? If you can't, you have a vacuum leak. *Excessive clearance between throttle shaft and throttle shaft bore in base plate. See if you can make the idle speed go up and down by moving the throttle shaft. Excessive clearance here causes a vacuum leak, raising idle speed. *Loose carb, causing vacuum leak. ------------------
'70 Mustang Mach 1, '72 Mustang Sprint, '94 F-150
Pics
MCA Member # 47773
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68 S-code GT
Gearhead Posts: 2416
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 07-08-2002 09:48 PM
It��s not the spring because I have that off along with the linkage it connects to.The engine stalls out if I close the choke up so I guess there is no vacuum leak. I��ll have to check the throttle shaft but I have to pull the pan first. Whoever built the engine put the oil drive shaft in upside down. I just pulled the distributor so I could jump it over one more tooth and I heard a clank. The shaft pulled up out of the pump and fell into the pan.  At least I now have a good excuse to check out the bottom end. 
quote:
Originally posted by SteveLaRiviere:
Things to check:*Excessive clearance between throttle shaft and throttle shaft bore in base plate. See if you can make the idle speed go up and down by moving the throttle shaft. Excessive clearance here causes a vacuum leak, raising idle speed.
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68 S-code GT
Gearhead Posts: 2416
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 07-08-2002 09:53 PM
It looks free of any obstruction but I��ll try your idea anyway! 
If that doesn��t work or Steve��s idea I guess I��ll pull the carb and try to see if the butterflies can be adjusted at all.
quote:
Originally posted by Jeff:
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Moneymaker
Administrator Posts: 25539
From: Lyons, IL, USA
Registered: May 99
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posted 07-09-2002 02:13 PM
Check the SECONDARY throttle adjustment. They are probably open a touch. You need to remove the carb to adjust the set screw. ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
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SteveLaRiviere
Administrator Posts: 42859
From: Saco, Maine
Registered: May 99
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posted 07-09-2002 08:14 PM
I was gonna say that next... ------------------
'70 Mustang Mach 1, '72 Mustang Sprint, '94 F-150
Pics
MCA Member # 47773
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Moneymaker
Administrator Posts: 25539
From: Lyons, IL, USA
Registered: May 99
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posted 07-09-2002 10:17 PM
 ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
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68 S-code GT
Gearhead Posts: 2416
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 07-10-2002 07:42 AM
Where exactly is it?  I was initially thinking of that but this is the first 4300 that I��ve ever played with so I��m a little lost! quote:
Originally posted by Moneymaker:
Check the SECONDARY throttle adjustment. They are probably open a touch. You need to remove the carb to adjust the set screw.
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Moneymaker
Administrator Posts: 25539
From: Lyons, IL, USA
Registered: May 99
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posted 07-10-2002 10:53 AM
Passenger (choke) side in the throttle body, underneath. It is a set screw that hits a part of choke linkage that connects to the secondary. You have to pull the carb and turn it upside down. ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
IP: Logged |
68 S-code GT
Gearhead Posts: 2416
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 08-06-2002 07:26 AM
Well, I finally got the new pump and oil pan on the engine and instead of messing around with the 4300 I installed the 1850 from my FB on the coupe. It ran perfectly. I will still have to fine tune it but I guess my problem with the 4300 is with the throttle shaft. Is it the base that wares or the shaft?
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Moneymaker
Administrator Posts: 25539
From: Lyons, IL, USA
Registered: May 99
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posted 08-06-2002 10:20 AM
Usually both. ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
IP: Logged |
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