Another Issue with an Edelbrock 1406

[dznucks]

The 1406 on my 350 has started having new issues recently that have me stumped. The issue is only at idle. Cruise, Power, and WOT modes are perfect, the A/F stays at a pretty steady 12.8-13 throughout.

The idle tune seems to be changing on me and thats where I am .

Here's the typical senerio.....the idle will be typically too rich, A/F 12-12.5, which causes it to be hard to start. I'll get home after work and retune the carb to an idle A/F of 13.5, anything lower than that is too rich and causes a hard start. It will be idling fine, timing is steady at 12deg, vacuum is high at 19" and steady, so i shut it off for the night. the next morning when i go to work, it will fire right up. Once the engine warms and i pull up to a red light, the idle A/F will be 12.5-13. at the next light it may be a steady 13 or it may be 12.5 at the light after that. When i start the truck at lunch or after warm starting it, it idles extremely lean, 16-17, or spiking out above 17, until the truck gets warm. Then the idle A/F goes to 12-12.5. And again at every light it seems to have a different A/F. so, I once again reset the tune when i get home from work, which always ends up with the mixture screws in the same position and the next day its the same story all over again.

I have checked for vacuum leak, i have repeatedly cleaned and blown out the carb, rechecked the float levels, checked the IMS passages, fuel pressure is at 4.5psi, plugs, wires and dizzy (HEI) are all recently replaced and seem to be operating fine. I am running 1" 4-hole carb spacer.

Does anyone have any other suggestions as far as what to check or look for?

[crakarjax]

What is your timing set to? Do you have an electric choke?

[68Stepbed]

That's why I quit using and won't ever buy another Edelbrock carb. 5 out of 5 that I've had just had screwy stuff like that all the time. None of them would keep an idle tune.

My SA Holley has kept the same tune on it for 3 yrs with no issues.

Sorry I'm not helping your issue. Hopefully someone will help.

[Ben IV]

Originally Posted by 68Stepbed

That's why I quit using and won't ever buy another Edelbrock carb. 5 out of 5 that I've had just had screwy stuff like that all the time. None of them would keep an idle tune.

My SA Holley has kept the same tune on it for 3 yrs with no issues.

Sorry I'm not helping your issue. Hopefully someone will help.

Amen, I could tune mine every other weekend but it wouldnt keep a tune. I swapped it out for a holley street avenger and smooth sailing since. I know this isint the answer you are looking for but after fooling with my edelbrock for a year i was fed up.

[dznucks]

Will do Stano.


Is there any way a cracked head or blown head gasket could cause this?

A buddy mentioned that might be the problem, but it doesnt make sense that it is running fine except at idle.

[D-Rat]

Originally Posted by dznucks

The 1406 on my 350 has started having new issues recently that have me stumped. The issue is only at idle. Cruise, Power, and WOT modes are perfect, the A/F stays at a pretty steady 12.8-13 throughout.

The idle tune seems to be changing on me and thats where I am .

Here's the typical senerio.....the idle will be typically too rich, A/F 12-12.5, which causes it to be hard to start. I'll get home after work and retune the carb to an idle A/F of 13.5, anything lower than that is too rich and causes a hard start. It will be idling fine, timing is steady at 12deg, vacuum is high at 19" and steady, so i shut it off for the night. the next morning when i go to work, it will fire right up. Once the engine warms and i pull up to a red light, the idle A/F will be 12.5-13. at the next light it may be a steady 13 or it may be 12.5 at the light after that. When i start the truck at lunch or after warm starting it, it idles extremely lean, 16-17, or spiking out above 17, until the truck gets warm. Then the idle A/F goes to 12-12.5. And again at every light it seems to have a different A/F. so, I once again reset the tune when i get home from work, which always ends up with the mixture screws in the same position and the next day its the same story all over again.

I have checked for vacuum leak, i have repeatedly cleaned and blown out the carb, rechecked the float levels, checked the IMS passages, fuel pressure is at 4.5psi, plugs, wires and dizzy (HEI) are all recently replaced and seem to be operating fine. I am running 1" 4-hole carb spacer.

Does anyone have any other suggestions as far as what to check or look for?

One of the issues I posted about had to do with hard starts when warm. Is your carb bolted directly to the manifold, or do you have a carb spacer? As I understand it the heat transfer could be boiling fuel out of the bowl. Even increasing the temp of your fuel will create more of a lean condition. Not sure if this is your issue or not. I don't have a way to measure A/F on mine, but the symtpoms sound similar.

I have a plastic spacer on the way that I'm hoping addresses this. My carb is brand new.

[cdowns]

have you checked the mounting bolts and retorqued them?

[foosed]

I too am I having problems with my 1406, vacuum leak. Hopefully the carb kit will take care of everything...

[dznucks]

thanks for the replies guys.


68shortstep, that is the conlusion that i have drawn with the edelbrocks, but my demon 625 is back at barry grant cause the secondaries wouldnt lean out with any jet change. I hope to be done with the edelbrock when and IF the demon will ever run right. i am about done with carbs, period.

i do have a 1" 4-hole phenolic spacer, i have had the fuel boiling issue and thats not the problem. the carb feels cold when the engine is warm and idling. i have read your post and i do believe that the spacer is going to help your (D-rat) issue.

the initial timing is at 12deg, max mechanical of 32, and the vacuum advance is giving me 18deg. its a new vacuum unit thats letting off at 15", the engine pulls 19-20" at idle.

it is an electric choke and that was a thought too, but i have jumped out and checked the choke when i have experienced the problem and its open.
and i have checked the bolts they are snug. the base plate is not warped either.

when i warm start the engine and its running lean like this, the only thing that i have found will change it is driving. reving it or letting it just idle will not get the problem to go away. i have fought this damn edelbrock every step of the way. every time i fix one issue its something else. thats why i am trying to get my road demon to run and i have reach my wits end with it on two occasions. thats why its back at BG with them going through it.

[dznucks]

Does anyone have any other suggestions of what may be causing this problem?

[Stano]

I am having trouble with my 1405 sounding similar to yours. I thought I had it beat but its back. I have rebuilt and cleaned all I am gonna, I am sick of it. I have ran these carbs for years with little to no issues but now I have two on the shelf and one on my 67 that all have issues. So I am looking for a real solution or a good replacement for it. If you find out anything on it let us know cause I do like edelbrocks carbs but I like to drive my truck more.

[68Stepbed]

No that shouldn't be the issue. I beleive it's a problem in the carb.

I tried a Demon carb once, it went back to them within two weeks. I never could get it tuned. I even called a professional, and he told me he wouldn't work on Demon carbs. He never could make em run right either.

[dznucks]

i am going to go back through the carb after work today.

It was acting up pretty bad last night, then on the way to work this morning (5 mile drive) it never gave me any issues. i bet at lunch it will go right back to acting up.

My demon ( most of the older demons) had alot of metal shaving in them left over from the machining. i removed all of that. The primary side of the demon runs so smooth and gave me plenty of power. but as soon as you got into the scondaries and WOT, it went to crap real quick. i jetted it down .015", primary and secondary, and still the same problem.

i have an old holley 600 on the shelf. the more problems i am having the more i am thinking about going back to it.

I am looking to do an LS swap and go to injection.......one day.

[mrein3]

Have you considered your fuel?

I don't know the laws in GA but here in MN the government mandated 10% ethanol in ALL grades of gasoline sold at ALL pumps here. EXCEPT for specially marked pumps that are to be used only for lawnmowers, snowmobiles, snowblowers, watercraft, and collector vehicles or vehicles eligible to be collector vehicles.

I know ethanol is trouble in my boats, lawnmowers, tiller, ATV, snowblower, etc. I always fill my jerry cans with ethanol free and my small engines always work right. My friends who save 10 cents per gallon by using the same stuff they use in their daily drivers are always taking their small engines in to have carb work done because the gas gets old.

The problem is smaller engines spend a lot of time sitting around. When ethanol sits around it separates and the water in the gas is what causes the problem. If your truck has the same gas in it for 2 weeks or more you can begin to see this.

Again I'm not saying your truck sits around and I don't know what GA does to you guys at the pumps. It just appears that you are doing all the right things and are still having issues.

[long69]

glad i'm not the only one on here that doesn't care for the ole' 1406.
mine ran real fine, but leaked gas onto the manifold.

[dznucks]

Thats a good point about the fuel, that i didnt consider. i really dont know the answer to that or how to figure that out. However i dont think it has any in it. Also, i dont typically use one particular gas station either, just whoever is cheaper. My truck is a daily driver. i go through a tank every week, week and a half.

If this was the case would the engine still run fine at all driving speeds? Keep in mind this only happens at idle. As soon as i crack the throttle the A/F goes back to normal and the vacuum goes back steady.

Today at lunch it acted fine on the way home, but when i cranked it to come back to work it started acting up as soon as i cranked it. It acts like it has trash in the carb somewhere, but i have cleaned it our repeatedly. just for the sake of insanity, i am going to take it back apart and blow all the passages with compressed air.

[CSGAS]

Originally Posted by mrein3

Have you considered your fuel?

I don't know the laws....

x2, plus I haven't noticed anywhere that you've replaced your fuel filter, have you?

I've had to clean out the deposits and crap the "oxygenated" fuels leave behind when they evaporate or sit for a day, got used to rebuilding an old Carter Ball-and-ball every six months in Cali that NEVER got plugged up with anything before MTBE came along.

I submit that your truck sat one day after getting filed up with either "smog" fuel or you ran the tank down to the bottom, stirring up some garbage, then filled it up. Either way your filter sounds plugged and there's probably more junk getting into the float bowl after every time you clean it.

This junk is also possibly sticking between the tips of the rods and jets. Try rolling the tips on a flat, hard surface to straighten them and replace.

Notice that the issues I mentioned can actually arise on nearly any carb, even ones that are normally unstoppable.

[dznucks]

The dizzy springs/weights arent sticking. i thought about that too and checked it. i have had the timing light on its while it acting up and the timing is steady.

The fuel filter is new and its before the regulator and pressure gauge. if the filter was clogged the pressure gauge would be acting funny, but its steady at 4.5 psi. However i do wonder about the fact of the fuel companies switching from the winter fuels to the summer fuels may be causing the issue. over the winter i did add the A/F gauge and really fine tune the calibration. Its night and day difference between the engine of 6 months ago and the way it runs now. this problems just started happening one day.


Its not a rod or jet issue either as i have been moving the calibration around trying to find the right tune. the problem doesnt change with a rod or jet change.

I also thought about the butterfly shaft being loose causing a random vacuum leak. I checked it two days ago when i had the carb apart. It will not move at all while in the closed position. once you open them on up they do have alittle play, but that doesnt explain the idle issue.

i highly doubt it is carb icing. the issue will not start happening until i crank the truck at lunch or when i let it sit for 30 mins to an hour after running it. I dont notice it in the morning probably because the choke and fast idle are kicked in.

[68Stepbed]

I run the junky 10% ethanol stuff in mine and other than less-than-optimum performance and less gas mileage, mine still runs fine. Sometimes it sits for weeks at a time.

I might have to check on the non-ethanol stuff around here. As far as I know, all pumps have it unless it's specific race fuel, which almost always has lead in it. It would be nice to run the real stuff again.

[67chevemall]

Build a large sling shot and fire it at your enemies.

[68Stepbed]

Originally Posted by 67chevemall

Build a large sling shot and fire it at your enemies.

I'd like to get in on that!

[dznucks]

Help me find an fuel injected LS(something) and we'll see about shooting the 'brock out of a large sling shot.

i took some videos of what its doing, if i can figure out how to uplaod a video. is there something in the FAQ on how to do that?

[dznucks]

lets see if this works. i have never uploaded a video.....

http://www.youtube.com/watch?v=fdfOosJRAtg

[dznucks]

ok. it appears to have worked.

the center gauge is the A/F and the gauge on the right "boost" is the vacuum.

i tore the carb back apart and blew everything out. I couldnt find anything wrong with it.

once back together it seemed fine, but it always does when i start messing with it in the driveway. we'll see what happens tomorrow.

[crakarjax]

Hmm, have you checked that your air filter is clean? At higher RPM your fan will basically be blowing air into your air filter, which might mask the fact that it's dirty. At idle it would have no help. However, that still doesnt explain why it happens only sometimes when idling.