Gutted precat causes truck to run rough

Hey all, recently my truck blew a headgasket so i decided to do a teardown. I replaced headgasket, waterpump, cap and rotor, spark plugs and wires, and thermostat.
While i was in there i pulled off the pre-catalytic converter and gutted it. Not sure if this was a good idea now. I was hoping to gain a couple hp and better top-end.

I have a Weber 32/36 carb on there and i just cant seem to get the thing to idle smooth. Has a hesitation when you blip the throttle so not sure if rich or lean. Any ideas guys? I've been messing with the screws with no results. Thinking i may have to rejet...

Thanks in advance

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I've run a Weber DGEV on my B2200 for about 9 years, has always run smooth. Both my converters are gutted too, and the little pipes all removed. Otherwise stock.

Question: did it run the same before the head gasket issue and gutting of the converter (assume it had the Weber then) ???

Ran great beforehand. A little lean but that was just me squeezing mpgs...

I didn't think the cat would affect it that much and your post proves it!
It has an acceleration issue where it stutters and will speed up, bog, stutter, then speed up again. Best way to describe it.

have the weber at 2 turns on the throttle screw and 4 turns on the mixture to even RUN. horrible, i know.

Any thoughts on what this issue could be?

Four full turns on the mixture screw is a lot. So my guess is that you are sucking in air somewhere, a vacuum leak, common with Weber installation. Did you remove the Weber or its adapters recently? I had a vacuum leak on mine, even with Permatex Aviation on the gaskets (re-used gaskets). Since I was too impatient to order new gaskets (now I have some extras), I took Dan Woodland's advice and cut new ones from rubberized gasket material (used Permatex on those too).

Now - in hindsight or new learnings - I know that I should've checked/sanded the adapter plates absolutely flat using wet/dry on a sheet of glass, to eliminate vacuum leaks. The sealing surfaces on these are really small, so everything has to be just flat.

Also check all your vacuum caps, they can crack and/or break off. Better quality ones or use a piece of vacuum hose and a wooden golf tee, or rute two nipples together.

Hey cusser,

Little update. I replaced the fuel filter and that took most of the acceleration stutter out but its still running lean. Takes forever to get up to 60mph and just doesn't seem to have much power.

I didn't change anything about the weber. The only thing removed was the intake manifold and i have a new gasket on it and it is torqued to spec.
I sprayed carb cleaner around the intake and i couldn't get the idle to raise indicating vacuum leak.

So my question is, what do you think could be causing it to not want to accelerate? was a little on the lean side before the rebuild but still ran strong and pulled in overdrive. Now it doesn't.

The first thing I'd do is go back and make sure that you're not off one tooth on your cam timing. Your description sounds like the cam is running one tooth late.

You can try using a vacuum pump to pull 14 psi on the vacuum capsule and see if it holds the vacuum. When they quit working they will give symptoms like what you are describing.

The other thing you might want to check is your valve clearances. You lost your back pressure when you gutted the pre-cat and maybe you are getting too much flow through the head so I'm guessing that is where some of your lean out is occurring.

Good luck.

Woah thanks Tweaker for the awesome advice. Will try those tomorrow.

I had marked the timing belt with nail polish so i don't BELIEVE it's off but i will definitely check!

i don't have a vacuum capsule. I bought the truck without it and installed the weber.

How would i adjust the valves to compensate? Cusser said his ran fine after gutting

Thanks

Make sure that the Weber throttle opens fully when the pedal is all the way down/throttle cable check.

Yes, on mine gutting the converters did not impede performance. I wonder if you're also getting enough fuel pressure and fuel volume.