New carb advice

84_GT350 · 01-28-2001, 04:25 PM

Ok...I'm sick of my carb. It's running way too rich and I've spent way too much money chasing this problem (I think it's a sinking float but nobody can varify that). ANYWAY...I'm gonna get a new carb. I just can't decide on a size. I could get a direct replacement for the one I have (Carter 625cfm) but I always wondered if that was too big and bogging the motor. I mean, it's not a whole lot more built than a stock motor. Should I go with a 600cfm Holley or stick with the 625cfm rating and get a Road Demon or something?

------------------
1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

Bob · 01-28-2001, 06:55 PM

If it's an automatic, go with a Holley 600 vac. secondary. If it's a stick car, go with a Holley 650 double pumper. You won't get the mileage with the d.p., but you'll get better performance.

------------------
1985 Mustang GT

'85 GT 13.20 @ 105.8 / '72 Mach1
Long list...check website!!
My Website

Five0 · 01-28-2001, 10:49 PM

I don't know much about carb's but I have been doing some reading on them and from what I have read I would have to agree with Bob.

------------------
James Cox
nochevy@hotmail.com
1991 Mustang LX
12.565 @109.38mph 1.764 60ft

juiceman · 01-28-2001, 11:15 PM

you can get decent gas mileage with a dp as long as youre not heavy on the gas and make the secondaries open. for a stock motor a 600 is plenty. anything more is overkill. before you ditch the old carb do these - remove float and hold under water in sink. if it bubbles it has a hole. next, blow out the air bleeds on the carb. also if you rebuilt it before are you absolutely sure you used the correct gaskets. they all look alike but have tiny differences to them.

gtstang83 · 01-29-2001, 12:01 AM

i switched mine to the holley 650 dp and love it. only thing i had to change was to put on the electric choke...other than that, i have been very happy with the results.milage is ok as long as your foot isnt of the heavy sort,and it serves well in the Get up and go dept.!!

Five0 · 01-29-2001, 01:52 AM

I have the 650 dp on mine too, I recently did a efi to carburetor swap and I like it more than I did the efi. If I could just get it tuned right it would be even better. I have a large cam and the carburetor does not like it very much and I get run on after it shuts off and sometimes it backfires. I read at Holley’s site that all I have to do is drill a small (3/32") hole in the throttle blades and turn the idle back and it should fix this problem.

------------------
James Cox
nochevy@hotmail.com
1991 Mustang LX
12.565 @109.38mph 1.764 60ft

79Stang · 01-31-2001, 08:35 PM

Your getting run on? What type of gas are you running???

------------------
°79Stang° • 351w, TRW Flat Tops, Comp Cam 270h,Edelbrock RPM Intake,
Holley 750 Duel Feed, MSD-6a, 2,500 stall,
Flowmasters, MaC shorties, B&M Shift Kit, Hurst Pro-Matic][,
DrAgLiTES on all four's
No Times yet - heads on the way

Five0 · 01-31-2001, 08:55 PM

93 octane
The carb already has the holes so I took it back to my friend and he rebuilt the carb and shortened the timing curve on the distributer. I don't know which one fixed it but it runs good now and even feels like it runs a little stronger.

79Stang · 01-31-2001, 10:59 PM

My bet would be the timming curve - bad timing or octane will diesel a car...

84_GT350 · 02-01-2001, 11:33 AM

Well, I've just broken down and had the damn thing fixed. Also turns out that one or more of my plugs are fouled since the car ran so fat for so long and now there's not as much gas. Oh well, live and learn.

------------------
1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

01-28-2001, 04:25 PM	#1
84_GT350 Registered Member Join Date: Apr 1999 Location: Overland Park, KS, USA Posts: 1,631	New carb advice Ok...I'm sick of my carb. It's running way too rich and I've spent way too much money chasing this problem (I think it's a sinking float but nobody can varify that). ANYWAY...I'm gonna get a new carb. I just can't decide on a size. I could get a direct replacement for the one I have (Carter 625cfm) but I always wondered if that was too big and bogging the motor. I mean, it's not a whole lot more built than a stock motor. Should I go with a 600cfm Holley or stick with the 625cfm rating and get a Road Demon or something? ------------------ 1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

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01-28-2001, 06:55 PM	#2
Bob "Old School Gearhead" Join Date: Oct 1998 Location: Peru, Illinois Posts: 617	If it's an automatic, go with a Holley 600 vac. secondary. If it's a stick car, go with a Holley 650 double pumper. You won't get the mileage with the d.p., but you'll get better performance. ------------------ 1985 Mustang GT '85 GT 13.20 @ 105.8 / '72 Mach1 Long list...check website!! My Website

01-28-2001, 10:49 PM	#3
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	I don't know much about carb's but I have been doing some reading on them and from what I have read I would have to agree with Bob. ------------------ James Cox nochevy@hotmail.com 1991 Mustang LX 12.565 @109.38mph 1.764 60ft

01-28-2001, 11:15 PM	#4
juiceman Registered Member Join Date: Jan 2001 Location: ny Posts: 197	you can get decent gas mileage with a dp as long as youre not heavy on the gas and make the secondaries open. for a stock motor a 600 is plenty. anything more is overkill. before you ditch the old carb do these - remove float and hold under water in sink. if it bubbles it has a hole. next, blow out the air bleeds on the carb. also if you rebuilt it before are you absolutely sure you used the correct gaskets. they all look alike but have tiny differences to them.

01-29-2001, 12:01 AM	#5
gtstang83 Registered Member Join Date: Oct 1999 Location: new windsor,ny Posts: 75	i switched mine to the holley 650 dp and love it. only thing i had to change was to put on the electric choke...other than that, i have been very happy with the results.milage is ok as long as your foot isnt of the heavy sort,and it serves well in the Get up and go dept.!!

01-29-2001, 01:52 AM	#6
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	I have the 650 dp on mine too, I recently did a efi to carburetor swap and I like it more than I did the efi. If I could just get it tuned right it would be even better. I have a large cam and the carburetor does not like it very much and I get run on after it shuts off and sometimes it backfires. I read at Holley’s site that all I have to do is drill a small (3/32") hole in the throttle blades and turn the idle back and it should fix this problem. ------------------ James Cox nochevy@hotmail.com 1991 Mustang LX 12.565 @109.38mph 1.764 60ft

01-31-2001, 08:35 PM	#7
79Stang The Stang Gang Join Date: Jan 1999 Location: St. Petersburg Posts: 63	Your getting run on? What type of gas are you running??? ------------------ °79Stang° • 351w, TRW Flat Tops, Comp Cam 270h,Edelbrock RPM Intake, Holley 750 Duel Feed, MSD-6a, 2,500 stall, Flowmasters, MaC shorties, B&M Shift Kit, Hurst Pro-Matic][, DrAgLiTES on all four's No Times yet - heads on the way

01-31-2001, 08:55 PM	#8
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	93 octane The carb already has the holes so I took it back to my friend and he rebuilt the carb and shortened the timing curve on the distributer. I don't know which one fixed it but it runs good now and even feels like it runs a little stronger.

01-31-2001, 10:59 PM	#9
79Stang The Stang Gang Join Date: Jan 1999 Location: St. Petersburg Posts: 63	My bet would be the timming curve - bad timing or octane will diesel a car...

02-01-2001, 11:33 AM	#10
84_GT350 Registered Member Join Date: Apr 1999 Location: Overland Park, KS, USA Posts: 1,631	Well, I've just broken down and had the damn thing fixed. Also turns out that one or more of my plugs are fouled since the car ran so fat for so long and now there's not as much gas. Oh well, live and learn. ------------------ 1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s