Previously, I was getting about 150 per tank. Still not the best, but I was dealing. After fixing my rear sag with blocks ~2 inches, just a temporary $20 fix till I get the money. And also replaced the idler pulley bearing because it was squeaking. It's now tough to get even 100 miles out of a fill up? Distributor cap & rotor look brand new. Spark plugs looked fine so I didn't replace them. Timing chain was done by dealership about 5-6 months ago, many gaskets replaced at that time and fuel pump and vacuum advance. I can't figure this out, and I can't keep driving like this.
Should I check after getting tires aligned?
All stock on 32x11.5

What is your compression?

you got a hole in your gas tank or something bud 100 miles a tank you need to do some reuilding or something thats nuts. you should be gettin 3 times that

I haven't checked compression yet but I haven't lost any power either. Theres no hole in my gas tank. I would had noticed that way before.

Check your tires for sure, pressure, alignment, but that wouldn't make it drop that much. Does it smell like its running rich? I would start at the carb. Have you changed plugs/wires lately? Air filter? All those things together could effect MPG.

Spark plugs looked fine when I pulled them a couple months ago, wires weren't changed but I dont see them affecting it be 5mpg. Pressure is about 26 on tires but I haven't messed with it since my mileage has dropped. It's always been running a little rich, but it's a aftermarket carb and I can't seem to get it tuned perfectly, neither could the mechanic.

Assuming stock 4.10 gears, that is a major mileage hit w/ 32" tires on there. First off you are actually driving further than your odometer indicates, how much farther? About 32/28 or 8/7 or 14% farther. Then you are driving about 14% faster than your speedometer indicates, so higher speed = higher wind drag = lower MPG. And your engine is having to work 14% harder than stock and is spinning 14% slower than it should.

Ive been running it with stock gears for a while now, and I was getting 160 miles a tank with these tires, something else took the major hit.

you said the vacuum advance was worked on? when was that work done compared to the drop in mileage?

fuel filter or fuel pump? less skinny pedal?

Vacuum advance was oem replaced. Was done at the time of the timing chain job.

lol What are you smoking? ON a 22R?!?! 200 miles on the 13 gal tank is cutting it close. EFI might be more impressive, but carbs are very inefficient compared to the direct-port injection.

Have the valves been properly adjusted since the timing chain replacement?

I would go through valves and ignition timing (8deg BTDC - 1984 Calif. 22R)

For the carburetor, you can adjust the mixture using a vacuum gauge. There are different kinds of vacuum ports: one where pressure remains almost consistent and one where pressure changes depending on engine speed.

Find a vacuum port that changes with engine speed (a.k.a. mess with the throttle as your checking ports with a vac gauge).

Once she's hooked up study the vacuum gauge response to your mixture screw adjustment. Enrichening and leaning out the screw results in a drop or increase in vacuum pressure (not sure what does what, but you can figure it out). However, the vacuum pressure will only max out SO much.

So, adjust your screw to the point where pressure JUST maxes out and won't go any higher. THAT is about where you wanna be.

Good luck!

I just bought a $350 honda accord beater for my daily driving. This truck will just be a project for another time when things settle money wise. Needed a new carb eventually and a cat.

Well do you have the 22r? If so you might need to have your carb. rebuilt. If you have the 22re then maybe you need to use some fuel injector cleaner.
Hey i might be wrong but thats what I think.