What is the best way to know if you've tuned your Carb right?

[hopp150]

Just rebuilt the stock 2150 and I'm trying to find out if I've tuned it right. It seems to run smooth but is there an easy way to know if it's running too rich or too lean with out waiting for plugs to build carbon?

Thanks!

 

[sprdv1]

LOL, just rebuilt my 2 barrel too.. Kinda winged it.... Some smart person will tell us..

 

[Broncobowsher]

Idealy you would use an exhaust gas analizer. Check you CO levels and adjust from there.

If you have a spare O2 sensor, put that in the exhaust, set up your volt meter and dial in around .4V

 

[ugly74]

go find a nice long stretch of road with no traffic. put it in gear, and romp on it! pretend gas is 99 cents a gallon, and get it goin as fast as you can.
once you're goin as fast as you wanna go, turn the key off and bring yourself to a stop. pop the hood, pull a couple plugs and see what they look like. Instead of pulling all the plugs, I like to pull one from each corner of the engine. if the plugs are white, it's too lean. if they're black or real dark brown, it's too rich. you're goal is a light tan.

or if you're really lazy, just look at your tailpipe. it should be just a bit sooty

 

[NYLES]

74's on it! Ole school but the way its done. if it obviously rich youll smell it at the pipes

 

[Explorer]

I don't understand the reasoning behind it, but the instructions on my Holley 4160 600cfm says to hook up vacuum gauge to manifold vac and adjust the idle mix screws for max vac. reading. I'm not saying it works, but my plugs are just the right color. Could be just dumb luck.

 

[JoseyWales]

Idealy you would use an exhaust gas analizer. Check you CO levels and adjust from there.

If you have a spare O2 sensor, put that in the exhaust, set up your volt meter and dial in around .4V

That's very interesting!

 

[357Bronco]

I don't understand the reasoning behind it, but the instructions on my Holley 4160 600cfm says to hook up vacuum gauge to manifold vac and adjust the idle mix screws for max vac. reading. I'm not saying it works, but my plugs are just the right color. Could be just dumb luck.

Those are idle mixture, not your main jets. You could have good mix at idle and then have problems on other circuits. But thats how to start, good idle, and that gets eliminated for further tuning.

 

[fireman1749]

Mines set at 4 turns out on both needles and i can go out and just barely tap the ignition and it will fire

 

[Wyflyer]

go find a nice long stretch of road with no traffic. put it in gear, and romp on it! pretend gas is 99 cents a gallon, and get it goin as fast as you can.
once you're goin as fast as you wanna go, turn the key off and bring yourself to a stop. pop the hood, pull a couple plugs and see what they look like. Instead of pulling all the plugs, I like to pull one from each corner of the engine. if the plugs are white, it's too lean. if they're black or real dark brown, it's too rich. you're goal is a light tan.

or if you're really lazy, just look at your tailpipe. it should be just a bit sooty

X2 on that. It's called "reading the plugs". Do a websearch and you'll find more about it. I'll add the disclaimer to keep ugly74 from getting sued: Don't do this if you have a locking steering wheel or other loss of control issues associated with turning off the engine while driving

 

[Madgyver]

go find a nice long stretch of road with no traffic. put it in gear, and romp on it! pretend gas is 99 cents a gallon, and get it goin as fast as you can.
once you're goin as fast as you wanna go, turn the key off and bring yourself to a stop. pop the hood, pull a couple plugs and see what they look like. Instead of pulling all the plugs, I like to pull one from each corner of the engine. if the plugs are white, it's too lean. if they're black or real dark brown, it's too rich. you're goal is a light tan.

or if you're really lazy, just look at your tailpipe. it should be just a bit sooty

I used to do this after a pass on the 1320.....

 

[broncow72]

Go get the vacuum guage at the parts store, they're only a few bones. I can't remember if mine came with instructions but I know I found them somewhere. Oh I know, I got my instructions off the Edelbrock website under tuning a carb. Anyways... Look wherever needed for your application and it is a good idea to have a tach that is visible from the engine compartment. I bought a dwell meter for about $25 at the local parts house. If you go this route... ask the old guy 'cuz the younger bafoons (under 30) don't have a clue what they are. Essentially you want the highest vacuum at 800 RPM. You will also need to adjust the timing while doing the carb. Not too hard, just time consuming. Set the carb and then adjust the timing to the highest RPM and then readjust the carb. Once you get this dialed in do the road test and check the spark plugs as stated.

 

[Scrapper_MV]

I did a vacuum tune on my 351W with an Edelbrock 1403 a few days ago. I did it just like Broncow72 said and it made a huge difference! My timing was way late and my carb was way out of adjustment. The Bronco runs much better now and it even sounds better. I'm taking my vacuum guage with me to the Big Bear Bronco Bash this weekend, so I can fine tune for the altitude.

 

[ugly74]

X2 on that. It's called "reading the plugs". Do a websearch and you'll find more about it. I'll add the disclaimer to keep ugly74 from getting sued: Don't do this if you have a locking steering wheel or other loss of control issues associated with turning off the engine while driving

thanks! I didn't even consider that I was baring my ass to a potential lawsuit.

what's really dumb...is I actually did that once in my dodge truck. I killed the ignition to load up the engine with fuel...so that once I gave it spark again, it would go BOOM! (my purpose was to amuse myself by scaring the crap out of a herd of goats;D ) and wouldn't you know it, I was in the middle of a corner when I did it. by the time I got the steering unlocked, I was too rattled to laugh at the running goats%)

 

[sprdv1]

Good info guys....

 

[lonesouth]

I killed the ignition to load up the engine with fuel...so that once I gave it spark again, it would go BOOM!

Is this bad for the engine or carb? Sometimes i want to scare the piss outa a ricer or a-hol...

 

[NYLES]

It can turn your mufflers inside out! Ill say it aint good for it!

 

[Baja71]

Yup. A friend of mine blew his muffler wide open. Much funnier than the initial 'boom'.

 

[ugly74]

I was running 2.5" glasspacks at the time, and there isn't a whole lot of backpressure in those things, so it didn't hurt nothin. I have seen mufflers that looked like pillows because of stunts like that though.

what really cracked me up when doin stuff like that, is the reaction of the sheepdog. if he ever got a hold of me, he'd rip my throat out. he was pissed!;D