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Colorado Smog issue. Suggestions/Recommendations?

C

CampBrr

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Broomfield, CO
Long story short, 86K5 Blazer with a 350, 600cfm Edelbrock Perfomer Carb. It won't pass smog here in colorado. Blows too high in CO. The Limit is 40 and the lowest I've blown is 47 with the denatured alcohol trick, new plugs and wires and a 500 cfm carb. I'm at my wits end. Emmission waiver guy says, Edlebrock carbs are not emmission compliant and they won't grant me a waiver. He says I'll need to put a quadrajet in it. The problem with that is I don't know what size Quad was original as the engine was replaced by PO. On top of that, a lot of the vacuum lines/EGR, etc that ran to the quadrajet were removed. I don't want to spend more $ on putting a quadrajet in it and it not passing, but if that's the way to not have to dink around every two years, I'd do it. Funny thing was, it passed emmissions with the 600cfm carb when I originally bought the truck, did the denatured alcohol trick the next go around and it passed. Now 6 years later, new carb, plugs, wires etc and it won't pass. Got a new high flow cat, rejetted and lower metering rods leaned the hell out of it and still no go. Guess I'm asking for opinions on what to do next or an experienced carb person recommendation in the north denver area. Can't work on it in my garage as it has a bolt on camper and it won't fit!
 
Personally, if I were having trouble that would require me to buy a new carb I'd just swap to FI of some sort. I went TBI on my 85 for about $150 worth of junkyard parts (bought on half price day though) and love the ease of turnkey startups in the cold and no hassle emissions testing here in smog crazy CA.
 
Move south. We don't smog test gas cars in elpaso county.

If you are on the edge of passing, the high flow cat might be the issue. They are legal but do not work like the originals. If everything else is good, they are fine.
 
Ditto on moving south... Pueblo county has no emissions requirements.

If making a move isn't in the cards and the Edlebrock won't lean out further you got a few options. 1. Call Edelbrock tech support. They might be able to give some tips to correctly lean it up. 2, Ditch the Edelbrock all together for the Q-jet. They didn't have many different sizes (cfms) in the 80's so if you get one for your application it should be the right one. Get a factory manual and you can run the vacuum lines correctly for the EGR. The q-jet is a better carb in my opinion, tuned properly it should pass. Plus you'll pass the visual that they are not giving you a waiver for with the Edlebrock. 3. Dump the toilet and go TBI. It's kinda overkill, but in the end it will run cleaner. Or just say MAW and just do the LS swap...

Don't forget that CO emissions is not just from the fuel being burned. If you have any type of oil burning from leaking valve stem seals or poor ring seal your CO number is going to creep up. I had the same problem with my old 307 in my Nova. I had a whole procedure to get it to pass in Denver when I was growing up. I dumped the oil and went to 20w50 Valvoline racing oil. Thick oil can't get past the valve stems or rings nearly as easy. Next up, fresh plugs. With the amount of oil the 307 used, the plugs got crusty in a short amount of time. Crusty plugs means incomplete combustion and high CO readings. Then I leaned out the carb (q-jet) and bumped the timing slightly. Last thing was to dump a bottle of Wynns smog check in the fuel tank. Following the instructions, you got to get the engine up to Operating temp and get checked hot. So I would dump the juice in the tank, buzz down I-70 for a few miles and pull right up to get tested. Passed with flying colors.

Sounds like the smog cop is pretty much forcing the q-jet on you. Might be worth your while to try a couple of the other things and take it to another location. From what I heard the smog test locations are full of kids that don't know much and you might get lucky.
 
Believe me, I'd move to the west slope if I could or S for that matter, but not in the cards for now. Tried a heavier oil. I'm thinking valves also, as my compression is a tad low on a couple of cylinders. I'd have to do a soak test to see where the compression issue is. Means bringing it to a mechanic to have that done. Anyone know what size Q-jet was stock? Can anyone send me the vacuum diagram? Called Edelbrock tech support last month and the 1st thing they told me was ditch the 600. Too big for the 350, so went with the 500cfm. Ugh!
 
Another trick a local inspection station used to get my old 454 to pass CO was to pull the PVC valve out and lay it on the valve cover..

I used to put 4 bottles of isopropanol dry gas in a 1/4 tank or less of gas,advance the timing a hair,and screw the idle mixture screws in a bit to get my "borderline" engines to pass emissions..

The biggest problem in passing an emission test is getting the engine as hot as possible and keeping it that way--if you could drive right into the inspection bay right off the highway after a good 15 minute high speed "carbon blowout" ride,most engines would pass with flying colors--sit in a line waiting a half hour for your turn to be "sniffed" almost always results in a "fail"..
 
Don't know why they'd say a 600 was too big. Maybe Edelbrocks suck? Yes, that is a loaded "question".

GM ran Quadrajet 750's or 800's on all vehicles from the I6's up to the 454's. There were no other sizes, although sometimes you will hear 795 used interchangeably for 800.

Truck *305's* (the ones I've personally inspected) got 800CFM Q-jets, Monte SS's with the HO 305 got 750's lol. And the Olds 307's of the 80's got 800's as well. No interest arguing fact that can be independently verified by anyone via google. Or by the 20+ Q-jets sitting in my garage.
 
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I learned to love Q-jets as a teen before fuel injection was accepted by the Average Joe and generally dismissed as too hard to deal with and not capable of performing as well as a good carb. I doubt that I'll ever own another vehicle with a carb but if I did it would be a Q-jet
 
Outside of the big block Buicks and 500" Caddy engines back in the early 70's that had the 800 cfm q-jet, the rest were the 750 variety.

Your bigger issue than the CFM size is if your original setup had a computer controlled q-jet or not. I did a search through Napaprolink through my shop and it's listing both non-computer controlled q-jets and computer controlled q-jets for 1986. Knowing the option content would tell if it was one or the other. Look at the SPID label inside the glove box.

As far as the vacuum diagram goes, google image search is your friend here. Again, what it should be will be dictated by the option content. In this case for the emissions option code. Here's one:
0900c1528004c460.gif



If you think there is low compression and you were the one that checked it, you don't need to send it to a shop to have the leakdown test run. You can rent the tool. You just need access to an air compressor. Hit up one of the locals if you don't have one to help out. Bribe with food and drink...
 
Retard the timing a few degrees,won't run as well ,but will probably get it to pass,then put the timing back after your done with deq
 
Most Q-Jets are 750. The reason they were used on such a wide variety of engines is that Q-Jets work based on airflow need. They've got small primaries and large secondaries, so they can run a 6 cylinder without being too much carb but they've got enough flow to power that V8 when you boot it.
 
Got it pretty hot the last time as I pulled right in the bay after blowing her out on the highway. I may try the heavier oil and retarding the timing. I got her so leaned out she runs like crap. Funny thing is this is my hunting camp/ski chalet on wheels. I spend 1/2 hour driving this in the front range and she runs mostly in the mtns! Thanks for all the suggestions. This forum and it's members are GREAT!
 
Well, I was blessed with warm weather this weekend. Wound up rejetting carb and metering rods and it passed barely. Blew 34 with a 40 limit. Not sure what it'll do the next time around. Ideally, I was hoping to find a relatively unmolested F.I. 90 Blazer or Jimmy and my camper would just bolt on. Those are hard to come by. How difficult would it be to convert to TBI? Not sure a full FI motor is in the cards as that would involve computer, instrument cluster, gas tank etc. Input from the CK forum collective? Thanks again.
 
Done right the TBI swap is a bit complex, but IMO it's more time than anything else. If you find a truck unmolested/in good enough shape to grab everything you need for the EFI swap, it's probably in good enough shape to drive lol.

Seriously though, piecing the setups together is generally expensive. There will always be a few parts you can't find used, which will be exponentially more expensive than if they were. If the truck has a bashed bumper and fender, it's easier to fix that than it would be to swap TBI.

IMO there is zero point in going "halfway" with injection (mechanical timing, etc). Fuel injection is good because it's a system. You either embrace the electronics, or you don't and stay carbed.

Your '86 I believe has VSS (definitely if it has cruise control), so no cluster swap required. Fuel tank is not a requirement, but it's a good idea to get the baffle/sump. Unfortunately factory tank setup is best, but the innards are plastic and break often. Need the EFI sending unit/fuel pump, fuel lines, of course the TBI, ECM, and wiring. Ideally you'd get the motor too, because TBI is tuned to the engine/vehicle it's installed in, and is very limited in it's ability to compensate for changes to either the load on the engine, or changes to the engine. Federally to remain emissions legal you have to swap it all over. Engine and all emissions components. Which is fine if you have a donor K5, more complex if the donor is a 1988-1995 C/K, etc.
 
I would be curious how aftermarket TBI would do. I appears to be easier for some of us to tune, no chip burning required. I would use factory TBI fuel system parts to feed it. I don't know how it would do in an emissions test though. I wonder if the EGR would work since it is vacuum controlled.
With the number of people having good results with the aftermarket stuff, maybe the initial price would be less painful if the results came with easier tuning?
 
That's one thing I've not seen...how does the aftermarket stuff look to an emissions test? As long as there is no visual, I can't imagine it would do worse than a carb, but would definitely be interesting to see the sniffer numbers.
 
Tbi swaps are easy since the 87 up's had tbi. Its a standalone system with a 3 wire hookup. Add bung in exhaust for 02...rock auto for cheap fi tank and sender and away you go. I did the swap twice many moons ago. However with todays tech you can't beat and LS swap.
 
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