Another Issue with an Edelbrock 1406

[RichardJ]

Ditch the phenolic spacer or replace with an aluminum spacer.

When the air above the throttle passes the nearly closed throttle blade there is a large pressure loss and a temperature loss. When you start it in the morning the throttle blades are held open by the choke high speed idle cam and there is less of a pressure drop.

This sounds stupid even to me, but I think the carb is icing up.

Do a web search for carb icing and you will find most info is about small aircraft engines. An airplane can fly for hours on a warm day with no problems. When they cut the throttle on the landing approach, the carb can ice if they don't add carb heat.

[dznucks]

And when you say you blew the carb out, what do you mean?

i completely disassembled the carb and blew out all the passages, both ways. Yes i checked the idle metering screws.

What steel balls? the only ball i know of is the one under the accel pump squirter.

RichardJ, thats a good point. the carb feels very cool when the motors hot, but i have always run phenolic spacers. why would it just now start giving me fits?

where would the icing occur? is it something i can visually see if i yank the carb after letting the engine sit.

[RichardJ]

If that is the problem, humidity is the culprit. Humidity isn't exactly a constant. The moisture in the air is freezing.

>>where would the icing occur? is it something i can visually see if i yank the carb after letting the engine sit.<<

If you let the engine sit, the ice will melt. If you are able to see it, you will have to yank the air cleaner real fast and shine a flaslight down on the throttle blades while the engine is running. It would be hard to see on that carb because of the clusters, but you should see some frost on the venturi walls and throttle plate.
If you can get the problem to present itself in your drive way, you could blow hot air on the carb with a heat gun or hair dryer.

[shocker]

is it possible that the mechanical advance in the dizzy is sticking and is sometimes advanced and sometimes retarded? This would change idle, starting and driving characteristics

[JesseH13]

how about this today when i was working on my truck getting it started up my dad noticed the accelerator pump wasnt working onthe carb
the shop next door took it apart and thier was no rubber donut around the plunger. IT WAS A brand new edelbrock straight out of the box!!!!!

[packers05]

ice no kidding. could your throttle shaft be the culprit try and manipulate it at idle pushing it in different directions see if it is that or secondary partly open, after that pick yourself up a nice quadrajet and rebuild it with good part and mods you will never look back!

[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.