85 jimmy fuel and 4x4 questions

[Bcwkyle]

Got an 85 Jimmy 4x4. Carbureted that I'm having trouble with.

1) Fires up fast and easy cold. But struggles to fire after its hot. It goes eventually but man. Takes a few minutes.

2) Runs and drives fantastic. I drive it to work sometimes. Runs and idles well. Purrs like a kitten. But the 2x I've taken it off road, it starts to idle rough and what seems like a misfire. Sometimes when giving it a little gas across the parking lot it kinda revs up and down. But then I drove it 2hrs home and it was totally fine. Could this be a dirty carb issue? I do know there is currently no fuel filter. I've only had it a few months. Still shaking it down.

3) What is the best off road carb? I know fuel injected is best. But I don't have the money or time for that yet. I have a 350. Do I need to worry about CFM?

4) Lastly I am hearing a grinding sound when trying to engage 4x4. Like its engaged but slipping? Sounds like the diff or the manual hubs. not the t case. Do those locking hubs go bad? They are WARN. I did install now motor mounts and such. And the shifter and indicator aren't staying at the 2H spot. Could it be I just need to adjust the shifter linkage?

Any and all help on these would be so great. Thanks!

 

[Wes Harden]

The best off road carb would be the factory Quadrajet. Holley and the Edelbrock afb clone are not even close. There might be some newer carb model I am unaware that might be close or as good as a Qjet. If you run a qjet the cfm will not matter, that carb will give the engine exactly the cfm it can use, up to 750-850cfm. Depends on model used, but the 850's were Pontiac, and Buick carbs, they can be made to work with minor mods.

Quadrajet tips
As for the poor running you probably need to lower the float level. 7/16" float setting works good off road. To set the float level the top must be removed. Caution do not over tighten the front bolts. Over tightening these bolts will warp the bowl and air horn, then you have a junk carb.

Tuning adjustments. If the idle speed screw is turn in to far fuel will be drawn from the middle venture nozzles at idle, making rich run, and starting troubles warm. In order to get the idle speed right with out fuel drip from nozzles, Timing, and air fuel adjustment in combination.

 

[AZ79K5Project]

I’d check your fuel system for the rough idle. Fuel filter and fuel pump if it’s an electric pump. I have not personally experienced intermittent problems with a me mechanical fuel pump. It’s an all or nothing.

For the four wheel drive, check the hubs, front driveshaft and front differential. Lift and support the front and turn the front driveshaft. If you have automatic hubs, I’d start there. Don’t put it into four wheel drive and try to run it with the rear wheels on the ground.