Exhaust stinks!!!

[Telecasterjoey]

So before I put the truck away in storage (we've got 4' of snow on the ground) I found my truck exhaust really stinking. I know what burning oil smells like and its not blowing any smoke but when I stop at a light and the winds behind me the truck fills with this nose burning exhaust smell. I'm pretty good with rebuilding carbs I just rebuilt the q-jet and the truck runs great, tons of power, no hesitation or bog and the secondaries work like they should!

The smell is bad I wish I could e-mail smell lol Its sour and burns your nose, Its not sweet smelling like a 2 stroke, and its not burning oil.
Myself I think its lean but I'm not 100% sure how to fix it! I set the float level to 1/4" and then tuned the air mixture screws with my vacuum gauge its tuned up nicely but it STINKS!

I had a spark plug pic but I cant find it, The plugs are a nice tan colour not too hot looking and definitely not fouled

I guess my big question is: am I running rich or lean? I've had old car guys say both!

truck specs:
86 gmc 1500
1990 gmc 350 block
70's camaro aluminum intake
stock 86' q-jet rebuilt and re sleeved with cliff's performance kit.
hedman longtube headers
dual exhaust no catalytic converters.
Timing at 12*

Thanks a lot!

[INSIDIOUS '86]

That would be excessive hydrocarbons. How's the timing? Where is your vac advance hooked to?
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[Telecasterjoey]

Timings advanced but it doesn't knock, prolly round 12-15 with out the advance hooked up.

Advance is hooked up to the base of the carb so I'm guessing ported vac not full vac, but I've tried both with no noticeable change.


No cats.
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[INSIDIOUS '86]

What mods for the engine? Close to stock usually runs 8-10* initial for me
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[Telecasterjoey]

Engine is bone stock, 1990 gm 350. I tried retarding the timing a bit but it still stunk...

[Redcap]

Originally Posted by Telecasterjoey

Engine is bone stock, 1990 gm 350. I tried retarding the timing a bit but it still stunk...

Does it have cats?

[Telecasterjoey]

Nope no cats

[Wrecked1982]

if it smell bad and burn eyes and nose i guess its too rich, my 454 did that rebuilt carb, set timming correctly. and problem solved. i guess too rich cuz it barely made 4 miles/gallon before tune up.

[Telecasterjoey]

Mine gets decent economy and the truck runs awesome! When people drive it they're always surprised how fast it is. I have a good timing light, I'm kind of thinking its my APT needle in the carb, I removed it when rebuilding thinking my rebuild kits would have specs or a standard spec for setting the apt, And stupid me didn't count the turns out........

I may take the top off the carb and pop the plug above the APT and thread it so I can adjust it without taking the carb apart.

[motornut]

choke issues?
it's been so cold lately....
try it this week supposed to be 0 today,3 wednesday
parked the 79 yesterday....

[Telecasterjoey]

Naw not the choke, trucks away for the winter and I've got a manual choke set up. This thing was stinkin even in July lol
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[donut]

What you mentioned abt. the apt may be correct, it may be out of whack. I don't know how to properly adjust it though.
Far off thought, did you change gas stations?

[Dead Parrot]

Double check that your fuel pump doesn't have a slow leak. What I thought was an exhaust leak turned out to be a slow leak from the pump housing.

[Telecasterjoey]

Originally Posted by donut

What you mentioned abt. the apt may be correct, it may be out of whack. I don't know how to properly adjust it though.
Far off thought, did you change gas stations?

I know how to adjust it..... but i've gotta take the carb back apart lol
The gas station idea is a good one but I get fuel all over the place so I dont think that would be it.


I'll have to check the fuel lines but they're all brand new, Also its a solid exhaust smell if you stand near the exhaust you'll stink just like it....

[donut]

The gas station was a far out possibility, different stations, fuel is a little different. I noticed it more with my 2000 diesel. 1 chain I used to get fuel, had the exhaust burning very "sulphery". Change station and the smell went away...

[INSIDIOUS '86]

Well I'm sure the af is off. Sounds like the base mixture is off
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[Telecasterjoey]

Hey guys I know this is an old thread, but I finally found the stinky exhaust issue. Insidious was bang on when he asked about timing. I've been cleaning up the truck a bit lately and read an article about ditching the ESC controlled distributor, I found a great how to on 73-87.com showing how to keep the original hei distributor and converting it to not need the ESC.

Once I got my distributor apart I realized the mechanical advance was seized and my Vacuum advance diaphragm wasn't working.

Welp I got it all back together minus the ESC, with a new vac advance and the weights all freed up. And wouldn't you know it, the smell was gone, so at idle the timing was waaaay too retarded.

So there if anyone has stinky exhaust check your timing first.

Thanks guys.