my exhaust smells bad - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GreenMystChevy · 11-21-2003, 01:28 PM

There's no such thing as a stupid question, just a stupid person. Well, here goes my question.

My exhaust, well, it smells. It has a very pungent odor that smells like gas and/ or something a little different. It's pretty strong.

Basically I was wondering how normal this is and what might be causing it. I know most of my other old vehicles don't smell quite that bad and I know that exhaust does have a smell to it, but something about this makes me think.

The only thing I can think of is the carb running too rich and running a lot of unburnt fuel through my pipes. I know nothing about tuning a carb and how to get the mixture right if that's the case though.

Thanks for the help guys.

Moloko · 11-21-2003, 01:30 PM

If it burns your nose, its probably running too rich. Try messing with the adjustment screws. Then them in to the right until the engine starts running rough, then back them off to the left until it idles smooth again. Do that to both mixture screws. Then re-adjust your idle so it idles at 800 or so RPM.

bpmcgee · 11-21-2003, 01:33 PM

Moloko is right. Those are the idle mixture screws.

And, just for your information, there ARE stupid questions. For instance:

Do you walk to school or carry your lunch?

Brian

Tim Rich · 11-21-2003, 01:36 PM

I was thinking you might want to lay off the chili for a while...

jcab · 11-21-2003, 01:58 PM

Quote:

Do you walk to school or carry your lunch?

LOL

That is just about as funny as the reference to 'Socks on a duck' in another post.

You guys can always make me laugh!

whew.... I need some more coffee.....

gonebad2 · 11-21-2003, 03:43 PM

If you have access to a real accurate tachometer (digital works best), hook it up. Adjust your idle mixture screws until you hit the highest RPM. Work the two screws together while you are trying to hit the high RPM. Once you've hit it, re-adjust your engine idle speed to around 800-850 rpm.

GreenMystChevy · 11-21-2003, 03:44 PM

I walk to school and carry my lunch, am I weird

So are you guys thinking that the smell, the one from my truck, not me, is from it being too rich? Any other things that it could be? Would a weak spark also cause this? Anything else?

Thanks gonebad2- I will try to find a good tach somewhere, I've never heard of doing it that way.

oldsub86 · 11-21-2003, 08:07 PM

What kind of carb are you running? I am having the same issue with a 600 cfm Edelbrock carb. I have adjusted the screws several times as well as the float level etc. I think I may need to reduce the jet sizes in order to lean it out some. Anyone out there have a handle on this stuff? I would appreciate the advice too.

lukecp · 11-21-2003, 08:18 PM

I have found the most accurate and easiest way to adjus the idle mixutre on a carb is with a vaccum guage. I was able to get my truck idling much smoother when adjusting with the vaccum guage.

I just hooked up the guage, set the idle speed, and fiddled with the mixture screws until i got the highest possible vaccum at idle. Worked great!

airbrushguy · 02-21-2015, 05:51 PM

Where do you hook the vacuum hose to?

seattle gmc · 02-21-2015, 08:09 PM

Quote:

Originally Posted by airbrushguy

Where do you hook the vacuum hose to?

Disconect the vacum line going to the brake booster (if you have one) and hook vacum gauge there.

hamjet · 02-21-2015, 06:10 PM

Old thread, anywhere off the intake manifold thats drawing vacuum. Usually right under or off the carb plate.

11-21-2003, 01:28 PM	#1
GreenMystChevy Registered User Join Date: Jan 2002 Location: Woodinville, WA Posts: 513	my exhaust smells bad There's no such thing as a stupid question, just a stupid person. Well, here goes my question. My exhaust, well, it smells. It has a very pungent odor that smells like gas and/ or something a little different. It's pretty strong. Basically I was wondering how normal this is and what might be causing it. I know most of my other old vehicles don't smell quite that bad and I know that exhaust does have a smell to it, but something about this makes me think. The only thing I can think of is the carb running too rich and running a lot of unburnt fuel through my pipes. I know nothing about tuning a carb and how to get the mixture right if that's the case though. Thanks for the help guys. __________________ Jeremy '71 C-10 '72 GMC K2500 '72 Nova (Dad's) '70 Chevelle SS '55 Sedan Delivery Attempting to build up this here 4x4...make her real tall and purty...well, maybe just tall

11-21-2003, 01:30 PM	#2
Moloko Hoarding Rusty Objects Join Date: Aug 2002 Location: Slatington, PA Posts: 267	If it burns your nose, its probably running too rich. Try messing with the adjustment screws. Then them in to the right until the engine starts running rough, then back them off to the left until it idles smooth again. Do that to both mixture screws. Then re-adjust your idle so it idles at 800 or so RPM. __________________ 1985 Chevrolet K20 Silverado 1994 GMC Yukon Follow me on Youtube! - http://www.youtube.com/user/FuelInjectionSucks

11-21-2003, 01:36 PM	#4
Tim Rich Registered User Join Date: Apr 2002 Location: Kennesaw, GA Posts: 56	Re: my exhaust smells bad I was thinking you might want to lay off the chili for a while... __________________ Tim Rich Kennesaw, GA 72 Stepside 65 Must@ng

11-21-2003, 03:43 PM	#6
gonebad2 Merciless Butcher Join Date: Oct 2003 Location: CC Nevada Posts: 1,447	If you have access to a real accurate tachometer (digital works best), hook it up. Adjust your idle mixture screws until you hit the highest RPM. Work the two screws together while you are trying to hit the high RPM. Once you've hit it, re-adjust your engine idle speed to around 800-850 rpm. __________________ Your Bought And Sold....I Got Your Soul!

11-21-2003, 03:44 PM	#7
GreenMystChevy Registered User Join Date: Jan 2002 Location: Woodinville, WA Posts: 513	I walk to school and carry my lunch, am I weird So are you guys thinking that the smell, the one from my truck, not me, is from it being too rich? Any other things that it could be? Would a weak spark also cause this? Anything else? Thanks gonebad2- I will try to find a good tach somewhere, I've never heard of doing it that way. __________________ Jeremy '71 C-10 '72 GMC K2500 '72 Nova (Dad's) '70 Chevelle SS '55 Sedan Delivery Attempting to build up this here 4x4...make her real tall and purty...well, maybe just tall

11-21-2003, 01:33 PM	#3
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Moloko is right. Those are the idle mixture screws. And, just for your information, there ARE stupid questions. For instance: Do you walk to school or carry your lunch? Brian

11-21-2003, 08:07 PM	#8
oldsub86 Registered User Join Date: Dec 2002 Location: Canada Posts: 695	What kind of carb are you running? I am having the same issue with a 600 cfm Edelbrock carb. I have adjusted the screws several times as well as the float level etc. I think I may need to reduce the jet sizes in order to lean it out some. Anyone out there have a handle on this stuff? I would appreciate the advice too. __________________ 1968 Chevy - 292 with a powerglide

11-21-2003, 08:18 PM	#9
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	I have found the most accurate and easiest way to adjus the idle mixutre on a carb is with a vaccum guage. I was able to get my truck idling much smoother when adjusting with the vaccum guage. I just hooked up the guage, set the idle speed, and fiddled with the mixture screws until i got the highest possible vaccum at idle. Worked great! __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

02-21-2015, 05:51 PM	#10
airbrushguy Registered User Join Date: May 2010 Location: hawthorne, nj Posts: 217	Re: my exhaust smells bad Where do you hook the vacuum hose to?

02-21-2015, 06:10 PM	#12
hamjet Registered User Join Date: Apr 2013 Location: South Westerlo, New York Posts: 1,325	Re: my exhaust smells bad Old thread, anywhere off the intake manifold thats drawing vacuum. Usually right under or off the carb plate. __________________ Thanks, Joe.. 1969 C/10, 348 C.I., 3X2 bbl. V8, 2004r , LWB.



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