Hello Guys,

I'm new to the forums because of an issue I'm having with my truck. I was hoping some of you experienced guys out there might be able to provide some input.

My truck:
The truck is a 1986 F150 with a 351W + 4BBL carb. From what I gather, that was the pretty standard equipment. I bought it from a kid who fancied himself the closet mechanic. In the process of his "work" he ended up removing most (if not all) the emissions equipment installed on the pickup. (Can't find a catalytic converter on the exhaust line either)

It runs rough until it gets warm. Once warm, it doesn't necessarily purr, but it works like a champ and has power to spare. I accelerated up a hill one day, carrying 1100 lbs of garbage on the way to the dump.

When I turn it off, it does smell like it is running slightly rich.

Sounds like a great project, eh?

My Problem:
Thing is that I'm in the middle of a home remodel and am in need of a hauler right now. It's been about a year since I made the purchase and the tabs have come up due. Now I have to pass the dreaded emissions test. Due to scheduling conflicts, I asked my Dad to take it in during one of his off days. The truck failed by a small margin: exceeding CO2 limits 560ppm (allowed: 280ppm) on idle test only. It passed the cruise test with no issues.

My dad, being the go getter he is, took it down that very day to a "Certified Emissions Specialist" as directed by the emissions center. They told him the carb was "shot," that it wouldn't hold an adjustment and it needed a new/rebuilt carburetor. Then they quoted him an obscene price that I won't bother repeating here. They wouldn't even guarantee an emissions pass with the new carb installed.

I've been planning on doing some work and replacing some equipment in the future anyway (including the carb) but coming up on the Christmas season during a remodel is not exactly the time I hoped for this: both spare time and cash are at a premium these days. Additionally, considering this shop was quoting such a high price for the carb, I'm a little suspicious of their claim that the carb is totally unworkable. I've had individual dealings with this shop before and they're always on the high side of estimates for work.

So I ask you guys - without looking at it, are there any adjustments I can make which will help increase the chances of me getting it to pass emissions the second time, or should I bite the bullet right now and install a new Holley from Shucks?

Any info would be greatly appreciated. Thanks!

 

You should be able to install a cat. conv. and pass. muffler shop, no work from you. Their trying to ream you! if you failed by small amount w/ no cat, then you will pass w/ cat. smog inspections are govt. way of making money and removing older vehicles ( the ones we drive) from the roads, IMO...BS. your up in WA?...shouldnt be hard to pass.

 

I dont think a cat will lower co2...My 86 f350 didnt come with cats, I was thinking it was just the 350's though. If you can read the sticker on the valve cover it shoul say catalyst or non-catalyst, that will tell you if yours came with or without cats. My truck did have (gone now, no emissions testing here) an air pump though, I'm thinking thats what you need to get the co2 down.

 

It sounds like the carb may need to be rebuilt.

 

They put so much alcohol in the fuel now, all vehicles, lawnmowers, chainsaws, boats, etc. are having carb problems. The alcohol attacks the rubber parts of the carb, and also attracts water which starts corrosion and sticky gummy stuff to build up in the carb, especially if you let it sit around very much.

If I were you, I would go to JEGS High Performance - Your source for Edelbrock MSD Holley Mr. Gasket Moroso or Summit Racing - High Performance Car and Truck Parts | 800-230-3030 and look at their carbs, and buy a new one. I know that edelbrock sells some that are jetted a little leaner for emissions, I am not sure if Holley sells some that are a little leaner. Anyway, that's probably going to fix your problem, and make it run better and get better fuel mileage too.

 

Do not buy a carb it is more trouble then it is worth to tune it to pass emissions, especialy if it runs good now.

I'm sure you ment that the CO was to high not the CO2. CO2 (Carbon Dioxide) is good all engines even the cleanest ones pump out lots of CO2. CO (Carbon Monoxide) is highly regulated, it is toxic and the result of incomplete cumbustion [fuel HC (Hydrocarbons=hydrogen and carbon) combines with oxygen O2 to form CO2 and water H2O] generally from the engine running to rich. The solution is to simply adjust the fuel mixture at idle to lean it out a bit. This is generally really easy I am not sure what carb you have (probably the holley) idle mixture is adjusted with two screws either on the side or base of the carb one on each side, the easiest is to turn it in until the engine starts to stumble and then out a 1/2 turn, even better is with a vacuum gauge and adjust for leanest with highest vacuum. This should be done with the engine up to temp and in gear if it's an automatic.

Hope this helps

 

You might have to lean it out till it runs like crap just to get through emissions

 

This article shows in the second photo where the idle mixture screws are located on a 4180 carb.
And how to get access to them.

4180 Mods

Hope this helps!
And welcome to FTE

 

Leaking gaskets and power valves also cause carbs to run rich. I would rebuild it if it was mine, but some people do not have the experience or it sounds like in his case the time, to rebuild the carb he has.

Turning the idle screws is a good idea too, if they are not capped off by the factory.

 

They were plugged, but you never know if somewhere along the way those plugs were pulled.

I had real good luck rebuilding my carb this past spring.

 

All true gut these kind of issues will become aparent when the idle mixture can't be leaned out enough with the idle screws. Until then best to just adjust assuming everthing is fine, there are no indicators of these problems yet.

 

Thanks for the info guys. I've been reading when I get the chance to get online and been doing research on my own.

I can see the plugs over the idle screws are still set, so the carb is per-production. I figure if I'm going have take the carb off to chisel away the plugs, I may as well just install a brand new Holley with the screws located in the proper place and not dull my chisels.

So that one is out. I brought out the Chilton's manual and began following their carb tune up method from step one. You basically have to turn the engine on and off (on and off, and on and off . . . .) to maintain fuel pressure in the reservior while alternatively adjusting the fuel level manually. The fuel level was set pretty high at the onset since it would gush out of the fuel level viewport screwhole. Hopefully this means it was just dumping too much fuel into the engine, hell if I know.

Don't notice any change in driveability. We're experiencing winter weather now, so I see lots of exhaust condensation; but it doesn't deposit any soot on a white paper towel. I know that 560 ppm of CO won't darken the towel, but it's reassuring that I didn't make things worse.

So I guess it's going to come down to a emissions test, since I don't know where else to go to test my handiwork.

Took it out on the highway this afternoon once I finished and opened up all four barrels. I don't know what it is about this truck, but I just love to drive it.

 

Puts a mile on your face doesn't it? I used to love my '92 E150 with a 351w. It was fast enough that most cops wouldn't even try to chase me. I made it from St Louis MO to Columbus in under 6 hours one weekend and still got 13mpg doing it. I also miss my '79 Old with a Olds 350 and a 4bbl. That car would just glide. Dunno what top end was, never found it.

 

Hold on, back to square ONE. Did the first emissions test give you a report?

If so, is it in fact CO that was high?

Catalytic converters exist to turn CO into CO2. (carbon monoxide, which will kill you quickly if not poison you irreparably, vs. carbon dioxide, which will only kill you slower, and is quite enjoyable in Diet Coke and other beverages...)

If you don't have a cat, you are not going to turn CO into CO2 regardless of mixture.

Were there other tests for HC & NOX? If so, what were those numbers?

If you passed on those two, your engine is running fine (fine enough for the emissions test, I note your other issues of rough cold running which may be fixed with the idle adjustments etc) But even if you are running fine, you will not eliminate CO without a Cat.

 

X2 Thats what I noticed right off.