shaunbacon

i just recently bought an 83 pickup with the 38 weber as the title says. i replaced plugs, wires, distributor cap and many other basics as it had been sitting for a while. after that, it ran fine for a while but still felt very slugish (even for an old 22r). I checked the timing and it was way off, very advanced, though i dont remember exactly what it was. I set the timing according to the chilton manual i have which says 13 BTDC with vaccum lines connected to the distributor. Now it run a whole lot better and it has a little more kick to it than it did before.

It'll drive fine with no problems as long as i dont push the gas pedal past a certain point. But if i push the pedal past that certain point (almost flooring it), the motor starts to lose power and backfiring through the carb. At that point, if i let off the gas and get back on it slightly, it will run fine. But if i stay on the gas, it will eventually start backfiring through the exaust(afterfiring?) and shoot what appears to be black smoke.

Whenever i do press the gas enough for it to start acting up while driving, even once, when i turn the ignition off it backfires loudly through the exaust. But if i drive it without pushing it to the point where it starts to act up, it wont backfire when i turn it off.

I've reset the timing step by step according to the manual twice so i dont think thats the problem. I've tried searching, but i cant seem to find anything with the same problem as mine and no solution. I have no idea what to do next. Any help would be greatly appreciated. Thanks in advance guys.

trevorthetrekker

Wow this is an old thread but it went unanswered so I'll take a shot at it.

I have a Weber 38 as well, and it sounds like your carb is out of tune and most likely needs to be jetted.

First of all get a Weber 38 jet kit here: http://www.lceperformance.com/Weber-...-p/1035006.htm

Yes it is expensive at $57 but it is absolutely necessary to get your 38 tuned correctly, prevent flooding, and increase stability.

The thing about the 38 is that both the speed screw and mixture screws need to be set correctly or else fuel will not get atomized correctly. The stock jets that come with it are very lean, so you most likely will need to turn out the mixture screws 2-3 turns, which backs them beyond their jet passage, so you end up with a stream of fuel just running into your venturi. This leads to fuel pooling which causes back and after firing.

To make it even worse, when the speed screw is turned in too much (idle speed too high), the butterfly valve will be sitting too open. This means instead of just the idle jet providing fuel to the engine, there are two transition ports in the venturi which are now allowing fuel in as well.

So, an improperly tuned 38 will be DUMPING in fuel from two different places. This is why most people end up saying that the 38 uses so much fuel. Before I jetted, it was running like crap and it would backfire and diesel on shutdown. I was getting under 10 mpg, more like 8.

After jetting, I can do burnouts with ease, the engine runs as smooth as any new electronically dependent engines out there, and I'm getting around 24 mpg.