cprstreetmachines

I don't understand how that would happen. The main well and idle circuit should be completely different circuits. Should have as much effect on idle as the jetting. If they do pop up, that should only add fuel to the main well, but not introduce more gas in to the engine until it's actually pulled through the booster. The idle circuit feed the engine from under the throttle blades.

4reboy

Hey Tad, when I get up to SLO you're going to have to educate me on carbs and possibly help me tune mine, I'll buy you lunch or something. I have a 650cjm Edelbrock, had it tuned before but now it doesn't seem to be running QUITE as well as it did a year ago. You know your carb by heart and I've seen you change your springs and whatnot so if you could pass along some know-how sometime that would be awesome I want to be able to tune my car WELL without having to pay, right now I can only get it to run decently if I mess with it, so I just leave it alone for the most part haha.

blue 67 coupe

Well I have to say I was a bit nervous at first after reading some of the comments about tuning and how holleys still run better after tuned. But after 2 trips to autozone I got the car started and didn't mess with anything except to set the idle lower. It sounded great and idle was smooth and didn't see any gas leaks so I took it for a test drive. It ran pretty great atleast 10 times better than the holley(wasn't tuned properly). The throttle response is quicker and all together it just felt like it took off quicker and has some really nice get up and go now.
Thanks to everyone that helped me fix some of the problems with the holley but all in all im glad I made the switch.

Starfury

There aren't two completely different circuits on an Edelbrock. The idle circuit feeds from the main well, so if the rods pop up while you're idling, the main well fills up and you get a rich condition.

At least, that's been my experience, and I've been told the same by others.

Local Yokel

Had a few Holley's over the years and never had a problem with them being unreliable? Had a 750 on a mild Big Block Chevy (the one the Edelbrock was on and removed) that I tuned myself and never had to touch. Also had a Procharged Chevelle making over 1000hp that I dialed in the Holley on and for the three years we raced the car we never had to adjust or open up the carb at all. I agree that the Edelbrock is a decent choice for a stock to mild motor but don't be afraid of the Holley. Once you take it apart a couple of times they're actually pretty nice carbs ....

cprstreetmachines

Not if oyu really think about it. A jet in a carb, any carb, will have no effect on the idle. The jet, and power valve/ rod feed the main well both. If a rod movement of power valve change were to happen, and actually changes the idle AFR's, the jet should do the same thing, but it doesn't. Think of the idle circuit like a dam, with a metered leak (idle mixture screws). You can fill the backside of the dam halfway or to the top, and it won't leak and slower of faster. It all depends on the size of the hole.Not taking into account the added pressure form the backside though. The idle fuel is puled with vac, and don't think there is any pressure on the backside of the mixture needle.

Starfury

Except there's pressure from the fuel level (gravity), plus atmospheric pressure. If there wasn't any pressure, you wouldn't be pushing anything out the other side. Because, strictly speaking, there is no such thing as a vacuum, simply a lower relative pressure than whatever is on the other side of the fluid being moved.

So, in theory, raising the fuel level will increase that pressure and make things run rich. That's what raising the float level does. More fuel in the bowl means more pressure and less distance that the fuel has to travel through whatever circuit to get to a nozzle.

I'm not being a smartass, just trying to figure out how these things work. I really do think it ran richer at idle with the 7" springs.

cprstreetmachines

That's what I was saying....it's such an insignifigant amount, 2-3 oz in a bowl isn't enough to force gas into the idle circuit faster than it's drawn out with 8-18 of vacuum. Even if it was, you raise the float level, or more in the main well, your adding 3 drops in a bucket. If gravity and atmospheric pressure was enough to make a difference, the carb would leak when the car wasn't running.

Raisng the float level can make a car run richer, but through the jets. It will also make the main circuit flow sooner. But because with a higher float level, it's easier to pull the fuel over. Not because any more pressure from higher float levels though.

kalli

i've tried a few different springs and measured the A/F while driving. but i don't recall having to adjust the idle mixture screws after changing rods, springs or jets. only when i messed with ignition or curb idle screw
edit: pity i don't have that edelbrock mounted anymore, could have measured that quickly