Thread: rich at idle

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I am working on my chevy 283 with Ebrock 600cfm carb....and it is rich at idle. i have adjusted it a couple of times per the manual and have noticed no difference. I did a search in the archive and came up the power valve may be bad. Any other options out there that I should be looking at? I did just finish putting the top end back on from a valve job, but this problem has been present before that little exercise I did buy the car used, so I have no idea of what may have happending to the carb previously. What about jets,,,,I would think the car would be small enough for a moderate small block chevy...it does have some cam to it and dome top pistons. How can I tell if it is rich at other times other than idle? Seems to pick up nicely and accelerate fine.

As always, thanks for the help in advance and happy spring weather riding to all!

Wander in, and have someone bring up the engine speed for a few seconds. if it seems to lean out at higher Rs, i wouldnt worry about it. but maybe thats just me.

It sounds to me like the power valve. Scoggin Dickey has Holley Classic 600 CFM Double Pumpers for $94.00, may want to check them out oh, there manual choke. Wait, it's an Edelbrock so, I don't belive it has a Power Valve, might be jetting. Check out the 600 CFM double pumper tho, there tried and true carbs.

Hey Buzz, buy a performance tuner kit from Edelbrock #1480, it has a manuel for fine tuning with it along with jets and metering rods, have fun!

If it is running rich, your metering rod springs are too strong for the vacuum of your engine or the jets and rod combo is out of wack!

Well I would really doubt that it is a power valve, because Edelbrock carbs don't use power valves. I know my 600 cfm one doesn't anyway, and I have never seen or heard of an Edelbrock carb that does. In fact thats one of Edelbrock's sales pitches is that they have "no power valves to fail".

Power valves are for Holleys.

I would check the choke. Is it electric or manual? If its an electric one, it may have died and can be causing the carb to run to rich. You may (or may not) notice it getting worse once the engine is warmed up.

Lotsa Luck,
Firechicken

yeah after looking into it, I see they have no power vavles...(my first Ebrock carb)...usually have Holley. The choke is manual, so that is not it..but thanks for the comments.

Nope, from my limited knowledge I am pretty sure that only Holley carbs have power valves, mostly all the rest use metering rods, and like Typhoon said they have springs in there that lift up the tapered rod to allow fuel in. Also, what kind of rpm are you running that 283 to, because that might even be a little more carb than you need? If it does lean out at higher rpms then its not such a big deal, but it could be that the metering rods and jets are sized for a bigger unit. Although carbs respond to air flow through them and only then do they add more fuel...if tuned right...it might be that at idle it is supplying too much fuel, which isn't a part of the main metering system in some cases. It is part of the idle circuit. So get those jets adjusted because the right jetting for your 283 with your 600cfm should also be the proper jetting for a 460. This may sound ludicrous, but the carb responds to more air, the more air it gets, the more fuel it adds. It's no doubt that the 460 will require more air, but the jetting will be the same, so get those figured out first. And check for vacuum leaks too. Hope this helps, good luck.