1406 Rough idle - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Bill72BB · 08-17-2002, 06:45 PM

Got the 1406 on just took it for a long drive run ok in town and on freeway .
Can't get the idle to smooth out ,followed the guidelines in the manuel but no luck.
The smoothest I can get it to idle is at 1050 rpm ,then when I place it in drive or reverse it idles like it has a cam in it and the rpm's drop to about 775 .

There is no hesitation on take off ,and accelerates and shifts real smooth .Choke is fully open.

Any Suggestion's on whats wrong.

Thanks Bill

68 Suburban · 08-17-2002, 06:47 PM

You sure you have all the vaccume lines plugged?

What are the specs of your engine? You might have to tune the carb.

Bill72BB · 08-17-2002, 06:55 PM

68

All vacuum line plugged or in use ,the engine is a stock 402 .

Thanks Bill

68 Suburban · 08-17-2002, 07:10 PM

Did you buy this new? I know that tuning the carb with the tuning kit can make a big difference. You can get the kit from Summit for about $33.

ChevLoRay · 08-17-2002, 07:22 PM

Easy way to check for vacuum leak: With it running, and the air cleaner off, simply place your hand over the air horn and try to smother it. If it dies, it ain't no vacuum leak.

Try turning the idle air screws in all the way, but be careful not to bottom them out...as this causes grooves to form in the idle are screws and makes virtually impossible to get the idle right.

Anyway, with the screws bottomed-out, (engine off, by the way) start backing them out 2 full turns (both of them). Then, start the engine. You have to have a reference point and this is it.

1406's are not supposed be jetted for performance, as the 1405's are from the factory.

Go to www.edelbrock.com, and check on their website for some help. It's there, if you look in the right place.

These suggestions are assuming the carb was new.

Q. Why did you go with this carb? I have a 1405 that I pulled off and replaced with a 750cfm Edelbrock 1901. I couldn't be happier.

Huck · 08-17-2002, 08:19 PM

Bill, I too had similar problems with my 1406. Two things helped---one was I found a vacuum leak near the elec choke --in the front casting section there is this thing that looks like you could put a screw into it----it was leaking vacuum. Second was that depending on your ignition system (HEI or regular), Edelbrock says to run your vac advance from ported vaccum (HEI)verses manifold vacuum.
To find the problem I installed a Vac gauge and it told me my vacuum should have been higher. I then used a small hose to listed for a leaking/sucking sound.
The VAC advance hookup goes to one of two ports on the front of the Carb. Assuming your timing is solid, try just changing to the other port and see what happens. Good luck~~huck

Bill72BB · 08-17-2002, 10:14 PM

Thanks ; ,Had to get the wife out to listen( I can't hear and refuse to get a hearing aid) ,she said she could hear some air ,did the hose routine it'sounds like its in the base gasket will replace tomorrow when the engine is cold '
This is ths Carb I had on my 82 that I sold a couple of weeks ago .put it on because my Q-jet was acting up when the engine was cold.

Thanks again will let you know if this fixes it

Bill

shortbed70 · 08-17-2002, 10:27 PM

I had a 1406 on my grand prix and it started that about a month after I bought the thing so I found out the base plate especially with aluminum intake was know to warp just enough to cause this rough idle so I bought a plate made by edelbrock(I think) from oreillys and some longer bolts and never had the problem again. Good luck.

bigjimzlll · 08-17-2002, 11:02 PM

I just had the same prob with my 1405..I took out the idle enrichment screws(all the way out) and shot some carb cleaner in the holes..that fixed it just fine

Bill72BB · 08-18-2002, 12:15 AM

Thats what I love about this forum itslike working on your truck with 500 friends who all have had some experience with what you are doing or having a problem with.

I couldn't wait till tomorrow I replaced the base gasket and that has fixed it, Idles smooth as a babys butt. That is what I get for trying to save a couple of bucks on a gasket.

Bill

Longhorn Man · 08-18-2002, 10:53 AM

Hey bill, a better way to find vacume leaks, esp if your hearing is on the poor side, is to spray carb cleaner at all the vac connections, and also at all the gasket surfaces. When the engine stumbles and trues to die, you found your vac leak.

08-17-2002, 06:45 PM	#1
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,979	1406 Rough idle Got the 1406 on just took it for a long drive run ok in town and on freeway . Can't get the idle to smooth out ,followed the guidelines in the manuel but no luck. The smoothest I can get it to idle is at 1050 rpm ,then when I place it in drive or reverse it idles like it has a cam in it and the rpm's drop to about 775 . There is no hesitation on take off ,and accelerates and shifts real smooth .Choke is fully open. Any Suggestion's on whats wrong. Thanks Bill __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

08-17-2002, 06:47 PM	#2
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	You sure you have all the vaccume lines plugged? What are the specs of your engine? You might have to tune the carb. __________________ Just sitting here contemplating contemplation.

08-17-2002, 06:55 PM	#3
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,979	68 All vacuum line plugged or in use ,the engine is a stock 402 . Thanks Bill __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

08-17-2002, 07:10 PM	#4
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	Did you buy this new? I know that tuning the carb with the tuning kit can make a big difference. You can get the kit from Summit for about $33. __________________ Just sitting here contemplating contemplation.

08-17-2002, 07:22 PM	#5
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Easy way to check for vacuum leak: With it running, and the air cleaner off, simply place your hand over the air horn and try to smother it. If it dies, it ain't no vacuum leak. Try turning the idle air screws in all the way, but be careful not to bottom them out...as this causes grooves to form in the idle are screws and makes virtually impossible to get the idle right. Anyway, with the screws bottomed-out, (engine off, by the way) start backing them out 2 full turns (both of them). Then, start the engine. You have to have a reference point and this is it. 1406's are not supposed be jetted for performance, as the 1405's are from the factory. Go to www.edelbrock.com, and check on their website for some help. It's there, if you look in the right place. These suggestions are assuming the carb was new. Q. Why did you go with this carb? I have a 1405 that I pulled off and replaced with a 750cfm Edelbrock 1901. I couldn't be happier. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

08-17-2002, 08:19 PM	#6
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	Bill, I too had similar problems with my 1406. Two things helped---one was I found a vacuum leak near the elec choke --in the front casting section there is this thing that looks like you could put a screw into it----it was leaking vacuum. Second was that depending on your ignition system (HEI or regular), Edelbrock says to run your vac advance from ported vaccum (HEI)verses manifold vacuum. To find the problem I installed a Vac gauge and it told me my vacuum should have been higher. I then used a small hose to listed for a leaking/sucking sound. The VAC advance hookup goes to one of two ports on the front of the Carb. Assuming your timing is solid, try just changing to the other port and see what happens. Good luck~~huck

08-17-2002, 10:14 PM	#7
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,979	Thanks ; ,Had to get the wife out to listen( I can't hear and refuse to get a hearing aid) ,she said she could hear some air ,did the hose routine it'sounds like its in the base gasket will replace tomorrow when the engine is cold ' This is ths Carb I had on my 82 that I sold a couple of weeks ago .put it on because my Q-jet was acting up when the engine was cold. Thanks again will let you know if this fixes it Bill __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

08-17-2002, 10:27 PM	#8
shortbed70 Registered User Join Date: Mar 2002 Location: Forney TX Posts: 4,512	I had a 1406 on my grand prix and it started that about a month after I bought the thing so I found out the base plate especially with aluminum intake was know to warp just enough to cause this rough idle so I bought a plate made by edelbrock(I think) from oreillys and some longer bolts and never had the problem again. Good luck. __________________ Troy 1965 Chevy Bagged,361 sbc,voodoo cam,1.5 full roller rockers,patriot 185cc vortec heads 2.02-1.60,vortec weiand polished intake,demon carb my truckhttp://67-72chevytrucks.com/vboard/s...d.php?t=332884 Big Red Dog build http://67-72chevytrucks.com/vboard/s...d.php?t=572274

08-17-2002, 11:02 PM	#9
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	I just had the same prob with my 1405..I took out the idle enrichment screws(all the way out) and shot some carb cleaner in the holes..that fixed it just fine __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

08-18-2002, 12:15 AM	#10
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,979	Thats what I love about this forum itslike working on your truck with 500 friends who all have had some experience with what you are doing or having a problem with. I couldn't wait till tomorrow I replaced the base gasket and that has fixed it, Idles smooth as a babys butt. That is what I get for trying to save a couple of bucks on a gasket. Bill __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

08-18-2002, 10:53 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Hey bill, a better way to find vacume leaks, esp if your hearing is on the poor side, is to spray carb cleaner at all the vac connections, and also at all the gasket surfaces. When the engine stumbles and trues to die, you found your vac leak.



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