rickc5

Several folks have expressed an interest in the results of my re-jetting of the new 36/38 Weber I installed on our '83 pickup a couple of months ago. I need to start by saying that we live near Grand Junction, Co at an altitude of about 4700 feet. I don't really consider this to be "high altitude", but I wanted to see if re-jetting made any difference at this elevation.

Likely some folks may be disappointed, but I only wound up changing the Primary Idle jet located on the right side of the carburetor. I went from a 55 to a 50--the smallest idle jet in the LCE kit for high altitudes (?), but 50 is the size recommended for our altitude. Now, this actually made a BIG difference. When I first installed the Weber, I bottomed out the idle mixture adjustment (all the way clockwise) trying to get the engine to run a leaner. It idled too rich with the 55 jet. The 50 jet enabled me to back off the idle adjustment about 1.5 turns or so, where I found that "sweet spot" where the idle speed was at the highest RPM and dropped off if I adjusted the idle screw in either direction. Perfect, IMHO. This jet change also really improved the transition from idle to acceleration in first gear. It no longer bogs slightly as I accelerate in first gear. Great!

I then took the truck for a long (10 mile) test drive and was very pleased with how it accelerated and ran. Being a staunch member of the "Don't fix it if it ain't broke" club, I decided I had done enough for now and put everything back together. I also discovered that instead of an "E" clip on the choke linkage as LCE suggested, I had a tiny cotter pin instead--maybe 'cuz I have a manual choke. Anyway, that tiny cotter pin just looked like a PITA to me, and it had to be removed to get the top of the carb off. So, would my mileage improve if I re-jetted the main jets? Maybe, but right now I'm totally pleased with how the truck is running and will drive it like this for awhile.


BTW- everything I read about the re-jetting process said to only make ONE change at a time, doing a test drive between each jet change. I feel this is good advice, and should I decide to experiment further down the road, I still have the jet kit.

millball

Would your mileage improve if you rejetted the main??? What mileage are you getting now??

rickc5

Since my odometer has been broken since I bought the truck in December, I have no way to calculate the mileage. However, changing to the Weber carb has noticeably slowed the decline of the gas gauge. I swear I could watch the gauge speed toward empty as I was driving along. So it's now better--I just don't know how much better.

millball

I'm a luddite myself, who only has a dumb phone that doesn't even take pictures, but I wager that you have a 'smart phone that contains a GPS.

You could get an app that will mark the miles you make with your truck.

L5wolvesf

Yes, ONE change at a time and doing a test drive and plug check between each jet change is the only way to know if the change you made went the "right" way or not. If you change more than one jet or component you wont definitively know which change was the "right" one or "wrong" one.

Part of correctly jetting a carb is getting it to function as efficiently (optimum mixture throughout all rpm ranges) as possible. If that is achieved then you will get the optimum MPG given your driving style.

4700 feet is at around the elevation where at least 1 step and possibly 2 might be needed. The different jets (idle, Main and ACs) interact differently with each other throughout the RPM range.

I don't recall which engine and/or mods you might have. But I believe I recall you had a pretty big air filter which would allow more air in vs the smaller ones some people use.

83

That's great to hear. I ran my stock Weber for a summer at 6,700' and surprisingly it did fine, but it was all dirt roads so I never really went over 45mph. Not the best test. I'll bet it would have ran a lot better with different jets, though. I had the opposite problem with my truck - odometer worked, but gas gauge didn't. So I could actually see what kind of mileage I was getting by watching the odometer, and have a good feeling for when I'd run out of gas. Though I did get surprised a few times...

rickc5

Actually, I'm not too different than you. Got rid of my antique flip phone only a year ago. Now I have the least expensive (cheapest) "smart" phone that has a very low IQ--not too smart. Not much memory either, so what little I have is already full of the few necessary apps I downloaded--like the flashlight app and the compass app--whoopee. To tell the truth, since the '83 isn't my daily driver, AND it's running fantastic now, gas mileage isn't important to me. At least I finally feel that I'm no longer pouring gas on the ground, as I was with the Aisin & smog stuff.