Edelbrock 1406 idles WAY too high on cold start... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**COBALT** · 05-04-2003, 09:38 PM

I've got this 1406 all set up for the most part with the fast idle adjusted, the choke adjusted (I think), and the mixture screws. My problem is when I do a cold start the engine wants to idle DAMN high. I don't have a tack, but the next thing I'm going to do is put it on, but I guarantee it's over 3000 rpm. It sounds like it.

This also raises a basic question about operation. I always pumped the accel once to set the idle cam on my old carburator before starting the truck cold. I did it with my little Rochester 2gv, but this is an electric choke so maybe I'm not supposed to be doing that. Should I just turn the key and let the choke do it's thing, or do I have to set the idle on the cam using the accelerator like I did with my other carb (which had the choke stove on the manifold)?

Finally, shouldn't the choke reduce the idle RPM when it's off (when the truck heats up enough for the choke to turn off)? It doesn't seem to be doing it. It just sits at high idle RPM until I pump the accel again and release the cam on the idle screw.

cableguy0 · 05-04-2003, 10:05 PM

well a lot of times the high idle seems a lot higher than it actually is and the way i have always started mine was to pump the gas twice to the floor let it idle it starts around 1000rpm then rises till i kick it off. just smack the gas pedal once after it is warm and it kicks it off high idle

MSL · 05-04-2003, 10:24 PM

Quote:

Originally posted by COBALT
I've got this 1406 all set up for the most part with the fast idle adjusted, the choke adjusted (I think), and the mixture screws. My problem is when I do a cold start the engine wants to idle DAMN high. I don't have a tack, but the next thing I'm going to do is put it on, but I guarantee it's over 3000 rpm. It sounds like it.

This also raises a basic question about operation. I always pumped the accel once to set the idle cam on my old carburator before starting the truck cold. I did it with my little Rochester 2gv, but this is an electric choke so maybe I'm not supposed to be doing that. Should I just turn the key and let the choke do it's thing, or do I have to set the idle on the cam using the accelerator like I did with my other carb (which had the choke stove on the manifold)?

Finally, shouldn't the choke reduce the idle RPM when it's off (when the truck heats up enough for the choke to turn off)? It doesn't seem to be doing it. It just sits at high idle RPM until I pump the accel again and release the cam on the idle screw.

My 1406 does the samething so i assume its normal for these carbs.

c-tenkid · 05-04-2003, 11:17 PM

Mine does to.

Also I am having something weird go on.

Sometimes my truck fires right up and idles fine.Other times it has to crank over alot.Then fires and wont idle.Any thoughts?

**COBALT** · 05-05-2003, 02:28 AM

No idea. Mine has never done that. It always kicks right up there unless I hit the gas again, and let the idle screw drop to the second step on the cam rather than the third.

Hm...guess I'll have to put up with it.

73stepside · 05-05-2003, 02:50 AM

i adjusted mine down to 1700 when you pump the gas. i had to adjust it with the engine running to get it right where i wanted it. mine did the same thing before i turned it down. i didn't lke waking everyone in the neighborhood up with my truck screaming at 2500rpm until i kicked it off the cold idle cam. it will take a little longer for it to warm up in the cold but it's not much.

gchemist · 05-05-2003, 03:21 AM

The choke startup should be no more than ~1200 RPMs. That's low enough to heatup an engine in a few minutes unless it's really cold. The electric choke need a slight throttle push to set itself when cold. Once the engine is warm or the throttle is stepped on, the choke will begin to open/close as necessary. Usually a slight tap will kick it down. Adjust the RPMs on the choke down.

**COBALT** · 05-05-2003, 12:36 PM

From the factory the choke housing is set one notch from center counter-clockwise. That's what was giving me the screaming RPMs. The manual says that the farther counter-clockwise (leaner) you turn it the longer the choke stays closed.

So should I turn it leaner or richer?

low 84 · 05-05-2003, 01:26 PM

there is a set screw on the driver side of the carb thats controlling your choke idle speed. i am NOT talking about the regular curb idle screw. there is one that rests on the choke cam. back it out and it will bring your choke idle speed down. richining or leaning the choke itsself by moving the housing to my knowledge is not going to bring your idle speed down except for the fact that if you lean it up alot your basically not using your choke anymore. with the air cleaner off rotate that housing and see what it does, all it does it change how far the choke blade closes thus if you richin it its going to shut the blade further when the choke is on.

**MikeB** · 05-05-2003, 01:29 PM

You need to adjust the fast-idle screw. This is from Edelbrock's website:

Fast idle may be adjusted to manufacturers specifications (usually 1500 rpm) during normal choke cold operation. The fast idle screw A can be adjusted with engine off and throttle held open to allow screw head access. Recheck fast idle speed after each adjustment.

The length of time during which the choke will stay closed is determined by the position of the choke cap. As the choke cap is turned clockwise the choke will stay closed longer. To properly set the choke turn the choke cap to the leanest notch on the choke housing, tighten the choke housing retaining screws, and run the engine until normal operating temperature is reached. With the engine running, slowly turn the choke cap clockwise until the choke valve begins to close. Now turn the choke housing one notch counterclockwise (LEAN) and tighten the choke housing retaining screws. Periodic readjustment of the choke will be required as the temperature changes throughout the year. After each adjustment verify that the choke valve opens fully after the engine is warm.

low 84 · 05-05-2003, 01:38 PM

screw "A" in mikes pic is the one i'm talking about

**COBALT** · 05-05-2003, 01:53 PM

Yeah, I follow you. Problem is I have that screw backed out almost to the point where it's falling out. When I adjusted the mixture screws I spent a significant amount of time trying to find my lean max RPM, and was able to get a good steady max RPM with the mixture screws, but my idle is still high.

You know I bet there's another problem. Maybe my throttle linkage isn't set up right...

I'm using a custom lokar kickdown for my TH400 + the return throttle springs and bracket. I had to adapt my accel. rod to the bracket with a gromet set. I remember having a tough time finding the throttle rod length. Maybe it's too short?!?

TIMSPEED · 05-05-2003, 02:16 PM

I gotta adjust my fast idle cam screw. Lately here, I'm having to adjust it manually, for it to warm the truck up at 1400rpm. It never turns off though, I always have to kick the throttle once, then it drops down to normal rpm...I always thought that was normal for turning off the fast-idle cam.

(I have the Holley 4160 with Electric Choke.)

73stepside · 05-05-2003, 08:31 PM

i have my choke set at the second notch from the end, or cab side which is c-clockwise. it runs fine and doesn't stay on too long. myset up is not the best or perfect. it was done to get it running good enough for the time being.

ZOOMY · 05-13-2003, 06:41 AM

If your fast idle cam isn't the culprit, then it must be the throttle linkage holding it open slightly....

**COBALT** · 05-13-2003, 12:18 PM

BINGO. ZOOMY hit it right on the head.

I have this fixed, but that ended up being part of the problem. I had everything adjusted right, and it still would idle high, so I got the engine to operating temp, and started actuating the linkage.

It turns out the accel rod from the gas petal was adusted too short. That's #1.

Also, the aftermarket return springs, kickdown bracket, and kickdown cable were coming loose. Turns out the Lokar bracket has a set screw in the side that holds the bracket square against the carburetor base to keep it from twisting. I forgot to install it, so the geometry of the return springs was tapering in just enough to catch the fast idle cam as I let off the gas. The steps were catching the throttle return spring! That's #2.

I basically took that whole corner of the carb loose, realigned it, tightened everything down, and adjusted the accel rod and kickdown. Now it works great.

Oh, and I also adjusted the electric choke 1 notch from the farthest setting counter-clockwise. The choke now cuts off right about when the thermostat opens. That's good enough for me.

05-04-2003, 11:17 PM	#4
c-tenkid Registered User Join Date: Apr 2003 Location: Festus mo Posts: 370	Mine does to. Also I am having something weird go on. Sometimes my truck fires right up and idles fine.Other times it has to crank over alot.Then fires and wont idle.Any thoughts? __________________ 69 c-10 lwb,Converted to 4x4,dana 44f,12blt,4 inch lift,vortec headed 355,th350/np203 34x10.50x15 swamper tsl's

05-05-2003, 02:28 AM	#5
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	No idea. Mine has never done that. It always kicks right up there unless I hit the gas again, and let the idle screw drop to the second step on the cam rather than the third. Hm...guess I'll have to put up with it. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

05-05-2003, 02:50 AM	#6
73stepside Registered User Join Date: Feb 2002 Location: Moore OK 73160 Posts: 974	i adjusted mine down to 1700 when you pump the gas. i had to adjust it with the engine running to get it right where i wanted it. mine did the same thing before i turned it down. i didn't lke waking everyone in the neighborhood up with my truck screaming at 2500rpm until i kicked it off the cold idle cam. it will take a little longer for it to warm up in the cold but it's not much. __________________ 04 GMC Sierra RCSS 70 CST LWB 04 HD Sportster 1200 Custom

05-05-2003, 03:21 AM	#7
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	The choke startup should be no more than ~1200 RPMs. That's low enough to heatup an engine in a few minutes unless it's really cold. The electric choke need a slight throttle push to set itself when cold. Once the engine is warm or the throttle is stepped on, the choke will begin to open/close as necessary. Usually a slight tap will kick it down. Adjust the RPMs on the choke down. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

05-05-2003, 12:36 PM	#8
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	From the factory the choke housing is set one notch from center counter-clockwise. That's what was giving me the screaming RPMs. The manual says that the farther counter-clockwise (leaner) you turn it the longer the choke stays closed. So should I turn it leaner or richer? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

05-04-2003, 09:38 PM	#1
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Edelbrock 1406 idles WAY too high on cold start... I've got this 1406 all set up for the most part with the fast idle adjusted, the choke adjusted (I think), and the mixture screws. My problem is when I do a cold start the engine wants to idle DAMN high. I don't have a tack, but the next thing I'm going to do is put it on, but I guarantee it's over 3000 rpm. It sounds like it. This also raises a basic question about operation. I always pumped the accel once to set the idle cam on my old carburator before starting the truck cold. I did it with my little Rochester 2gv, but this is an electric choke so maybe I'm not supposed to be doing that. Should I just turn the key and let the choke do it's thing, or do I have to set the idle on the cam using the accelerator like I did with my other carb (which had the choke stove on the manifold)? Finally, shouldn't the choke reduce the idle RPM when it's off (when the truck heats up enough for the choke to turn off)? It doesn't seem to be doing it. It just sits at high idle RPM until I pump the accel again and release the cam on the idle screw. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

05-04-2003, 10:05 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	well a lot of times the high idle seems a lot higher than it actually is and the way i have always started mine was to pump the gas twice to the floor let it idle it starts around 1000rpm then rises till i kick it off. just smack the gas pedal once after it is warm and it kicks it off high idle __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

05-05-2003, 01:26 PM	#9
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	there is a set screw on the driver side of the carb thats controlling your choke idle speed. i am NOT talking about the regular curb idle screw. there is one that rests on the choke cam. back it out and it will bring your choke idle speed down. richining or leaning the choke itsself by moving the housing to my knowledge is not going to bring your idle speed down except for the fact that if you lean it up alot your basically not using your choke anymore. with the air cleaner off rotate that housing and see what it does, all it does it change how far the choke blade closes thus if you richin it its going to shut the blade further when the choke is on. __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

05-05-2003, 01:29 PM	#10
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,420	You need to adjust the fast-idle screw. This is from Edelbrock's website: Fast idle may be adjusted to manufacturers specifications (usually 1500 rpm) during normal choke cold operation. The fast idle screw A can be adjusted with engine off and throttle held open to allow screw head access. Recheck fast idle speed after each adjustment. The length of time during which the choke will stay closed is determined by the position of the choke cap. As the choke cap is turned clockwise the choke will stay closed longer. To properly set the choke turn the choke cap to the leanest notch on the choke housing, tighten the choke housing retaining screws, and run the engine until normal operating temperature is reached. With the engine running, slowly turn the choke cap clockwise until the choke valve begins to close. Now turn the choke housing one notch counterclockwise (LEAN) and tighten the choke housing retaining screws. Periodic readjustment of the choke will be required as the temperature changes throughout the year. After each adjustment verify that the choke valve opens fully after the engine is warm. Attached Images __________________ Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

05-05-2003, 01:38 PM	#11
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	screw "A" in mikes pic is the one i'm talking about __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

05-05-2003, 01:53 PM	#12
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Yeah, I follow you. Problem is I have that screw backed out almost to the point where it's falling out. When I adjusted the mixture screws I spent a significant amount of time trying to find my lean max RPM, and was able to get a good steady max RPM with the mixture screws, but my idle is still high. You know I bet there's another problem. Maybe my throttle linkage isn't set up right... I'm using a custom lokar kickdown for my TH400 + the return throttle springs and bracket. I had to adapt my accel. rod to the bracket with a gromet set. I remember having a tough time finding the throttle rod length. Maybe it's too short?!? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

05-05-2003, 02:16 PM	#13
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	I gotta adjust my fast idle cam screw. Lately here, I'm having to adjust it manually, for it to warm the truck up at 1400rpm. It never turns off though, I always have to kick the throttle once, then it drops down to normal rpm...I always thought that was normal for turning off the fast-idle cam. (I have the Holley 4160 with Electric Choke.) __________________ I have a few cars... See Them Here

05-05-2003, 08:31 PM	#14
73stepside Registered User Join Date: Feb 2002 Location: Moore OK 73160 Posts: 974	i have my choke set at the second notch from the end, or cab side which is c-clockwise. it runs fine and doesn't stay on too long. myset up is not the best or perfect. it was done to get it running good enough for the time being. __________________ 04 GMC Sierra RCSS 70 CST LWB 04 HD Sportster 1200 Custom

05-13-2003, 06:41 AM	#15
ZOOMY Senior Member Join Date: Feb 2003 Location: WIS Posts: 1,752	fast idle If your fast idle cam isn't the culprit, then it must be the throttle linkage holding it open slightly....

05-13-2003, 12:18 PM	#16
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	BINGO. ZOOMY hit it right on the head. I have this fixed, but that ended up being part of the problem. I had everything adjusted right, and it still would idle high, so I got the engine to operating temp, and started actuating the linkage. It turns out the accel rod from the gas petal was adusted too short. That's #1. Also, the aftermarket return springs, kickdown bracket, and kickdown cable were coming loose. Turns out the Lokar bracket has a set screw in the side that holds the bracket square against the carburetor base to keep it from twisting. I forgot to install it, so the geometry of the return springs was tapering in just enough to catch the fast idle cam as I let off the gas. The steps were catching the throttle return spring! That's #2. I basically took that whole corner of the carb loose, realigned it, tightened everything down, and adjusted the accel rod and kickdown. Now it works great. Oh, and I also adjusted the electric choke 1 notch from the farthest setting counter-clockwise. The choke now cuts off right about when the thermostat opens. That's good enough for me. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.



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