Running rich

[Veefour]

I'm not all that great with mechanic type things, but I just bought an 85 K5 that needs some work so I think I'm going to be getting a crash course.
ANyway, It's running rich and I was hoping someone could explain to me what causes it and if there is a cure for it. I've noticed that most cars I've been around that were 20 years or older have this problem. ANyone have time to explain it a bit.

 

[89GMCSuburban]

How do you know it's running rich? What are the symptoms? Original carb, new carb, or TBI conversion?

 

[Veefour]

New carb I guess. Its an edelbrock.
The symtoms are that there are no fuel leaks, but the car has that distinct smell of gasoline rich exhaust when running.

 

[metto]

im going to hijack a little here cause i have a very similar problem. i need to change the fuel mixture on my edelbrock 650 cfm. there are 2 screws at the base of the carb, which one controls fuel mixture?

 

[89GMCSuburban]

Unless you have tuned a carb before, take it to a shop to get tuned by a professional. Carbs are picky, and if you don't know what you are doing, you can mess it up worse. Sounds like you need the needles played with a little bit. Take it to a local performance shop and get the carb tuned.

 

[89GMCSuburban]

I'm not sure which one it is, but when you find out, don't turn it too lean unless you want a hole eaten into a piston or two.

 

[metto]

i have access to a exhaust sniffer at work, i was going to use that to controll how much i lean it out

 

[google]

I've been having the same problem. Good thread. But to add to the question, how can you tell what carb and what CFM? Here is a pic of mine if it helps.

 

[ntsqd]

That would be a Carter AFB or the Edelbrock clone of an AFB. I've found that the Eagle cleaner for non clear coated mag wheels works wonders on them. DO NOT use this on a Q-Jet unless you hate it. And wear rubber gloves as most have Hydrofloric Acid in them, which exceedlingly dangerous in very low concentrations.

If it's a comp series AFB it should have a tag riveted to the front of the carb right where the filter can sits on it that has the CFM rating. Since you're asking I'm guessing it's either gone or unlegible.

If you know what you're doing in tuning a carb, this might help: http://www.dock.net/ntsqd/tech/Carter - Edelbrock Tuning.doc
If you don't I'll second the advise above about having a competent shop do the work.

 

[crazy_swede_73]

im going to hijack a little here cause i have a very similar problem. i need to change the fuel mixture on my edelbrock 650 cfm. there are 2 screws at the base of the carb, which one controls fuel mixture?

The two screws on the base is for setting idle mixture. at least thats what they are for on my edl 1405 600cfm carb.
go to http://www.edelbrock.com/tech/index.html i think they have a tech department where you can download Owner Manuals

 

[mountain4x4]

Yeah, download manual, call tech and ask them what parts you need. Its really easy, especially with Edelbrocks, but I'd check your tune at a Dyno with a wb o2 sensor for best results. You should be able to get a few pulls for around $50, worth every penny, just make sure the sensor is upstream of the converter if you have one. Parts and dyno time, about $100, youll make it up in gas savings very quickly, plus the guys at the dyno will probably be knowledgable and offer advice if needed.

I've found that the Eagle cleaner for non clear coated mag wheels works wonders on them.

C'mon, pulling the carb and rebuilding it is a job any amatuer wanna-be mechanic can pull off, don't just spray crap on it, do it right or don't do it at all.

 

[Veefour]

I know mine is an edelbrock because there is a really bright red label on the front of it that reads "Edelbrock". It's also sitting on Edelbrock's "Performer RPM" manifold. Don't know too much about it as of yet....just bought it. I'm guessing it's a 650 CFM. It's just a 305 without any internal engine mods so I assume anything larger would be too much. Then again, should it be a 700 or so, this could be the source of my rich problem....correct?

 

[mountain4x4]

The model # on Edelbrocks is stamped on the bottom front of the carb, check it out to see what carb is on there, it'll be a 4 digit #, 1405 is the 600 cfm carb I think. A bigger carb won't necessarily make it run rich, but low speed operation such as idle and low rpm throttle response will be affected, and it can dump too much gas near full throttle.

If you wheel your rig much, I've had better luck with Q-jets. Now might be a good time to get one before you spend time and $ on the Edelbrock. I'd just find a used one, theyre very cheap, and clean it out, install new gasket kit, and see how it does. A stock q-jet probably won't require any tuning. There is also lots of info on q-jet mods to make them even better off road. I owned an Edelbrock q-jet, very good carb...

If you keep the Edelbrock, you can get an off-road spring-loaded needle and seat, which helps.

 

[Veefour]

ok, my Carb has 1405 stamped on it, and behind that is 3430.

 

[dontoe]

If you keep the Edelbrock, you can get an off-road spring-loaded needle and seat, which helps.

That will be mandatory if you get on any kinda slope, I know from experience.


Setting idle mixture!
Setting the idle mixture is easy. Turn both screws in all the way, lightly, in to tight and ya mess up the seat. Turn both out 1 and 1/4 turns. That is close for near sea-level. Turn both equal amounts in or out to get the highest idle ( if you don't have a vacuum gauge, if ya do, get the highest vacuum) that's it other than resetting the idle speed screw.

 

[Mad-Dog]

Both of them are idle mixture screws.....turn each 1 in seperately until idle speed drops slightly then back em out 1/2 turn.
Adjusting the fuel mixture across the entire powewrband is very complicated
and requires needle/spring and jet changes as well as knowledge in carb tuning and a air/fuel ratio monitor.
NOT FOR THE FAINT HEARTED