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Emissions SUCKS !!! (updated)

4xcrazy

4xcrazy

3/4 ton status
Joined
Oct 31, 2003
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Location
Elma, Washington
Ran this P.O.S. through twice, with TWO different carbs and timing adjustments, and came back with very similar results,,,kinda wondering if the small tires with the 4.10's in the rear end are causing the motor to rev too high and pump out more emissions than allowable,,,,


I really hate this crap..:mad:

If ya wanna know,,,,,'81 C-20 2wd, with a semi-fresh rebuilt 350/th350, RV cam, headers, cats, true dual exhaust setup, and little tires, "ASSUMING" 4.10's by the way the motor rev's up real quick from take offs,,not a highway friendly truck...

Hydrocarbons @ 6.21 allowed 4.40...failed

Carbon Monoxide @ 115.38 allowed 48.00....failed BIG TIME

(NOX) @ 3.20 allowed 7.00,,,this is fine

just about ready to yank the motor and part it out like the original plan was to do with it.:mad:


OH, BTW, this same motor was in my Nova when it wasn't wrecks and still driveable, and pass emissions just fine,,,so i am kinda lost.
 
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I am not sure of you are supposed to have a smog pump. CATs perform the same function as a smog pump does. They burn up unburned gas. If this where an original 1981 Arizona Federal emissions truck, then it would be unlikely that your truck ever had CATs originaly. It would have been a leaded burning engine with an EGR and a smog pump like my 1985 K30, which is an original Nevada Federal emissions truck. The only way your 1981 truck would have been an unleaded burning truck with CATs is if it where from the Republic of communist California. The problem could be a bad carburetor, unless at least one of the carbs you are using is new.
 
That is what is throwing me off, i tried two different carbs, and they both came back with very similar readings, it would seem they should be somewhat different, even if they were both bad, it seems they should be alittle more off than they are.

I have a Edlebrock carb and manifold on another motor i am seriously thinkin about buying a re-jet kit and run it as lean as possible, it doesn't have the EGR valve though, but the NOX was already WAY lower than the standard, so i don't think this will be a problem as it wasn't even hooked up when it went through this second time.

I just don't know though...:confused:
 
Are these idle numbers or driving numbers on a loaded dyno?

Rene
 
tRustyK5 said:
Are these idle numbers or driving numbers on a loaded dyno?

Rene
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sorry bout that, driving loaded on the dyno

new style of test too, where they imitate actual driving with different throttle positions,,not like the older one where they'd hold it one rpm
 
its probly the true dual cats not heating up enough .
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That is a possabilty, because one CAT only recieving the exhaust gasses of one bank of cylinders may not be hot enough.
 
4xcrazy said:
sorry bout that, driving loaded on the dyno

new style of test too, where they imitate actual driving with different throttle positions,,not like the older one where they'd hold it one rpm
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They've always done the dyno test like that here...:crazy: and the diesel test runs almost three minutes long with a WOT "hillclimb" from 16 mph to almost 60 mph.

Anyways, if you lean it out too much the NoX will go through the roof. The truck was completely warmed up both times? If the choke is even partially engaged you'd get numbers just like that...maybe the choke is sticking a little?

Rene
 
I wonder if they are going to start dyno tests here in Nevada? That would be an expensive peice of equipment for the smog inspection stations, which would be passed onto the consumer...of course.
 
4xcrazy said:
I have a Edlebrock carb and manifold on another motor i am seriously thinkin about buying a re-jet kit and run it as lean as possible
Click to expand...

Why not just re-jet the carb you have instead of swapping manifolds and carbs??
 
Was going to try to re-jet the Quadracrap, but cannot get the metering rods and parts to do it very easily/quickly, the plugs/cap and rotor are all good,,,

i was chatting with a guy down at Carquest, and got to askin me about the "setup" so i told him, and we came to the conclusion, i may have the timing WAY too far advanced for this engine and cam setup, he was saying that alot of cams are already advanced by themselves about 4degrees or so, and then i went and advanced the timing some more from stock to try to counteract the hotter cam things that may happen.

So tomorrow i am going to throw the vacuum gauge on it, reset the timing alittle less than stock setting, and adjust the carb up from there all while watching the vacuum gauge:crazy:

As mentioned before, this is just too weird that two different carbs with same type of readings, but both run awsome driving down the road,,,,DAMN these Chevy engines LOOOOOOOVE GAS !:eek1: :D

will update at a later date, thanks for the replies...
 
Was going to try to re-jet the Quadracrap
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I can pretty much garauntee you that any factory GM Q-jet you are running is a wasted pile of crap. The fuel well plugs are probably dumping raw fuel into the intake manifold, regaurdless of how much epoxy or ceramic you may have on them. My guess is you have two worn out piece of junk carbs that are dumping raw fuel into the engine, which is why you are not passing smog. There is a saying: "you get what you pay for". if you have two used up carburetors, then you will never pass. I just went through the same smog hassle you are going through. I bit the bullet, and popped ($280) for a brand new Edelbrock Performer 750 CFM carburetor for my 1985 K30 with a 454, and my truck passed smog with flying colors.

So tomorrow i am going to throw the vacuum gauge on it
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Unless you "degree in" (with a degree wheel) an aftermarket cam to "true TDC", the only way you can properly set the ignition to valve timing is with a vacuum gauge (a timing lite will not do it) because aftermarket camshafts are not indexed to a factory crankshaft when ground, like a GM factory camshaft is. When you connect the vacuum gauge to a "MANIFOLD" vacuum source, advance the distributor until you reach max vacuum reading, then back it off 1/2-inch of vacuum, this will be the most efficiant timing you can get. If you have to retard your timing more than this to pass smog, then there is somthing more wrong with your engine, which is causing it to not perform as good as it should.
 
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1-ton said:
the only way you can properly set the ignition to valve timing is with a vacuum gauge (a timing lite will not do it) because aftermarket camshafts are not indexed to a factory crankshaft when ground, like a GM factory camshaft is. When you connect the vacuum gauge to a "MANIFOLD" vacuum source, advance the distributor until you reach max vacuum reading, then back it off 1/2-inch of vacuum, this will be the most efficiant timing you can get. If you have to retard your timing more than this to pass smog, then there is somthing more wrong with your engine, which is causing it to not perform as good as it should.
Click to expand...

this is the exact plan right here,,,i was so brain farted and dead yesterday, i just couldn't think straight anyways, now i am rested, when i get back from a light day of work, gonna tear into this..

will let ya know how it goes when finished,,thanks for the replies:D
 
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