help on Q-jet carb.

I like to look at the cost of gas vs how much I am delivering. With the season winding down, fuel is less than 2% of the price of the goods delivered. The driver costs me more than that.

One thing for fuel economy is cooler engines, but with todays HEI, they run pretty hot. I do remember back about '74 having a boss come out with a "fuel saver" that he began marketing. Wasn't much more than a sealed jug of colored water and alcohol that he tapped into a vacuum hose near the base of carb into the intake manifold plenum. Was clamped off so at best could trickle occasional drops of the concoction which was vaporized by the turbulance in the manifold. Did it make any or a big difference? I don't know. The users said it did. He was killed flying his 2 seater plane in to the side of a hill in a dense fog when he shouldn't have been flying, so it never went big. I've gotta figure did about the same as occasionally trickling a garden hose down a running "up to operating temp engine" - the cool moisture hits the hot carbon buildup, shatters it and sends it out the tail pipe. That goes back to a cooler running engine - hot carbon (heat) robs performance, although the newer ones require heat.

Try this, I posted a couple of weeks ago. I have diesels, so aint bothering. My brother told me he saw something on Speed Channel or one of them, where this engineer type says he's been doing it forever with great results. Said he added 1.5 ounces of acetone for ever 10 gallons of premium grade gasoline. Now hold on a second before you say "PREMUIM!?!". He said premium because that has more additives than the most volitale, regular grade, lesser volitale mid-grade, and least volitale premium grade. As I understand it, the acetone causes a chemical reaction in the milage robbing additives that pretty much makes them impotent, and the increase of milage more than offsets the cost of the premium. Supposedly makes the engine run cleaner (as she showed by tearing one down), and increases the milage. Supposedly, not much change was noticed in regular grade, some in mid-range, the most in premium. Try a Google Search and see if something turns up on "acetone gas additives" or the sort. May be something to it. Good luck.

Mark

And Slowpoke, I remember when I was an Illinois resident and they decided they were going to begin charging a "fee" for their smog test. That idea went over like a lead balloon, and didn't happen. Funny thing, was a "smog inspection", but had to pass everything else like turn signals, brake lights, etc. They say that "the vehical must be safe for them to get in it to smog test it". Uhh Huh, at 8.75% state sales tax on all parts that they can find fault with, revenue is revenue. Call me a cynic.

Mark

Before I messed with the carb the boat got about 2 mpg at cruise (19 knots and 2,750 RPM). After locking out the secondaries cruise performance remained unchanged, but "mileage" increased to 2.5 mpg - a 25% improvement.

As expected the top speed dropped (from 26 mph at 4,000 RPM to 22 at 3,200). But with gas running $4/gallon at the marina I'm happy to limit speed to "cruise" anymore!

Locking out the secondaries was a simple matter of bending a tang on the primary throttle shaft so it bypasses a mating dog on the secondary shaft. Secondary operation an easily be returned if desired by bending the tang back - though unless gas returns to $1 or less I doubt I will...

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If you can find 'em you can also try installing one or two sizes smaller jets in the primary fuel metering circuits. (Jets are marked by orifice size on the OD of the orifice head). But that's kind of a trial and error process. And if you go too lean you will have drivability issues and may risk engine damage (burned exhaust valves, etc).

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Good luck! Keep in mind however even latest, fuel injected 1 tons are good for only 10 - 11 mpg. To get better that you'll need to go diesel.

As far as mileage goes, if your air/fuel mixture is correct, the only thing that will really help is to carefully avoid opening the secondaries. Q-jets have very large secondaries and very small primaries. For most conditions, the primaries are all you need, but with an engine as big as a 454, I would not wire the secondaries closed, as someone might suggest. There are times you might need the added accelleration or power that you can only get by "kicking in the 4-barrel", like climbing hills and holding freeway speeds.

You might want to try a new float assembly to make sure your old one isn't sinking and that the float level is where it should be. And be very careful with the carb inlet fuel filter, if it is still there. It is extremely easy to cross thread that fitting when you put it back together. BTDT!

Some of the vehicles from the late 70's--early 80's had carbs jetted richer than necessary. I never really understood how rich jetting was better for emissions, but supposedly with the catalytic converters of the day, it worked better if they were rich. Maybe it had to do with oxides of nitrogen. Anyway, if you have access to an exhaust gas analyzer, you might check this possibility out. It would have to be checked prior to the catalytic converter, assuming your truck has one. If the analyzer shows that your mixture is richer than it has to be, you might be able to gain some mileage by leaning it out a bit. You would have to experiment with the jets/rods to get the perfect air/fuel ratio, which might be something to have a carb expert do.

Sometimes a new air filter and a good tune-up can pay for themselves with better mileage. Don't expect a huge increase though...unfortunately the big, heavy carburated pickups with big engines generally don't get much more than about 10.

That is about what I get with my 460 powered F250 4x4. And I wish it had a Q-jet on it. Good luck!

I don"t know what you have on it now, but most factory systems could use imrovement. Free flowing duals will heip, and you don"t need to have it loud either- large RV type mufflers can be had that will not restrict flow and dampen the noise.

Also, look into a multi strike iginition box. I have never met anyone running one on a carburetted engine that did not notice a fuel mileage improvement. MSD, Mallory, Accel and Crane all make them. Fairly easy to install and wire. For your uses don"t spend the extra money for one with rev limiters etc., a Mallory 6A can be had for $119 from most mail order speed shop type outfits.