'86MM G63B & Weber 38 Dges tuning issues

[nprboref]

Here I have my '86 MM, recently I completed what I've been calling a re-ring and re-seal of the motor. I had previously swapped to a Weber 38dges and while it did run rich before the rebuild It never fouled the plugs. Granted I only had about 1000 miles with the weber before I blew the head gasket. Now it coughs and sputters to the point where it's undriveable. I did change my exhaust by putting a header and full 2.5" exhaust, it has a cat and muffler in line. I feel like that is what is causing it to run like this because it will idle fine but once you try and give it gas it suddenly is upset at you.

I had been messing with smaller jets because the plugs had been pig rich but those actually made it worse.

It had 55 idle jets but I dropped those to a 50 and it idles nicer
So i returned the carb to how I got it and the jets are as follows

145 Main Jets
170 Air Corrector Jets
50 Idle jets

I haven't looked at the accelerator pump jet yet so that might be causing it as well as it seems to do it any time I try and give it more than a minuscule amount of gas.

If anybody has any input or is running a similar setup I'd love to hear from you, thanks for your time.

[SubGothius]

I gather Webers tend to give running trouble when they're too lean, whereas too rich they run mostly okay, just dirty with poor fuel mileage.

Evidence of a rich condition (like sooty plugs) can be misleading, as that could also be due to a lean misfire. If you had access to an exhaust analyzer, this would show high HC and low CO, whereas rich would show both high.

BTW, the idle jets aren't just for idling; they also serve most low-RPM driving, then the mains start to come into play at mid-high RPMs.

[xboxrox]

Nice truck !!

Does it have cruise control ? Drivers inner fender has a large round diaphram actuator looking piece?
Good luck tuning the carb.
Welcome here too

[nprboref]

She does have an aftermarket cruise control in her, it stopped working but when I was working on it I found one of the wires to the pickup on the speedo cable was split so I soldered that back together. The guy who put it in put it right above the valve cover and I have yet to put it back there which is why it is sitting up by the brake booster currently mostly unhooked.

I'll have to ask around people I know to see if they have a combustion analyzer. If nobody I know has one I may just end up buying bigger main jets and seeing what happens.

[mopar_ja]

did you resolve this issue

[nprboref]

The issue isn't 100% resolved as of today. The current setup is 161 main jets (I had 2 sets of 145s so I drilled a set with a #52 drill bit which is 0.0635 in. or 1.61MM) 50 main jets and 170 air corrector. It's good enough to drive with light to medium throttle but It bogs occasionally. Under very light throttle it bogs and starts bucking really bad. Also, before today if I held a full throttle pull it fell on its face completely at about 5-5500 RPM. And then today I was tweaking my idle and I went to rev it and if I hold it at full throttle it breaks up really bad and sounds like I have a 2Step at 3000RPM. I need to get a timing light on the truck and see what my initial and total timing is. Ideally I'd hope to get my hands on a combustion analyzer but those ain't cheap and I don't anybody with one. It might be worth it to get a wideband o2 sensor and install it to see my afr's.

[geezer101]

Installing an O2 sensor will go a long way into dialling it in.