Tuned it but still running too rich

[DanWheeler]

302 w/ edelbrock 600 carb (I think) headers and glass packs

I've tuned it using a vacuum guage and got it running at what I thought was lean best idle but I'm getting a ton of carbon (or something else black) spewing from the exhaust. It's not noticeable as smoke in the air but if I park the truck next to something (like my clean white car) it makes a huge black splotch after a minute or so.

any ideas whats going on here? Is there something else I can do to tune the carb and make sure its at lean best idle?

thanks,
dan

 

[broncnaz]

Thats pretty normal for a carbed engine there will be carbon buildup in the exhuast system for a while. Also you need to tkae it out and run it down the road do a full throttle run then check your plugs if they are black then you need to rejet it.

 

[DanWheeler]

thanks

yeah, i wouldn't be surprised if it were jetted wrong. Am I looking for wet black or just dry carbony black? DO i need to clean the plugs before I do the test?

 

[70_Steve]

I've tuned it using a vacuum guage and got it running at what I thought was lean best idle but I'm getting a ton of carbon (or something else black) spewing from the exhaust. It's not noticeable as smoke in the air but if I park the truck next to something (like my clean white car) it makes a huge black splotch after a minute or so.

The carbon is not from idling. The carbon is built up in the exhaust system while running at part throttle, like while driving normally. It blows out the exhaust when you start the engine because the cold exhaust system condenses the water vapor in the exhaust gas and that water washes out some of that built-up carbon.

The Edelbrock/Carter AFB are pretty easy to change the Air/Fuel ratio on. Just drop in a leaner set of metering rods. Takes maybe 5 minutes to do, and most of that 5 minutes will be R&Ring the air cleaner.

Wet and black is an indication of being oil fouled. Dry black powder is carbon from being too rich. No real need to clean the plugs before starting.

 

[DanWheeler]

that makes a lot of sense - I've mostly noticed this problem after first starting it up but i'll have to see if it still does it after everything is warmed up. thanks for the info.

 

[eb66to77]

You can get a metering kit for the Edelbrock Performer Series carbs easily from your local Advance or Pep Boys or ? for pretty cheap. I think 60 bucks and it comes with three different setups. I ahve one for mine but haven't dicked with it at all.

 

[70_Steve]

You can get a metering kit for the Edelbrock Performer Series carbs easily from your local Advance or Pep Boys or ? for pretty cheap. I think 60 bucks and it comes with three different setups.

Or, just pull the metering rods and look at the number on them. Then just buy one set of metering rods for much cheaper that the Strip Kit that I bought for $70!!

 

[DanWheeler]

Is there a good way to find out if i'm too rich though? besides reading the plugs? that seems like it could be pretty subjective and not very accurate.

 

[70_Steve]

Is there a good way to find out if i'm too rich though? besides reading the plugs? that seems like it could be pretty subjective and not very accurate.

Reading the plugs is more accurate that you'd think. Off the top of my head, the only other options are to have O2 bungs welded into your exhaust, then hook up and O2 sensor with a meter. I think Summit Racing sells this setup. Or, you could spend the bucks to schedule some Dyno time at a shop with a wide-band analyzer and tune the carb there.

 

[DanWheeler]

ok, i'll try the plugs. So if my plugs are dry and carbony i should try the next smallest metering rods?

definitely don't want to bother with the 02 bungs - i bought a Summit digital O2 gauge for another truck and it was fun to watch but mostly useless.

 

[BG's 68 Bronco]

ok, i'll try the plugs. So if my plugs are dry and carbony i should try the next smallest metering rods?

definitely don't want to bother with the 02 bungs - i bought a Summit digital O2 gauge for another truck and it was fun to watch but mostly useless.

it will be useless unless it's wide band.

 

[70_Steve]

So if my plugs are dry and carbony i should try the next smallest metering rods?

Actually, you would want the next larger metering rods. The metering rods fit down into the jets. The larger the rod, the less open area for fuel to flow, the leaner the mixture.