Setting up the new carb--pointers?

[F250 Restorer]

I have a newly rebuilt QJ from 78.  I kept all the settings, mix, idle, secondaries that it was set at for a sbc.  I did change the m. rod piston spring to one with more tension since it is going on a 309 ci ford I6. 

I'm hoping someone here would be so kind as to give me a basic step by step guide with this.  I've worked on carbs before, but this is by far the most complicated.  I'd appreciate any help offered. 

Thank you.

[Cliff Ruggles]

Stronger springs simply start the power piston up earlier when engine vacuum drops off sharply.  In most cases, use the strongest spring that will have the power piston down at idle, as it will get it moving up the earilest and quickest when you hit the throttle hard, or any situation where the engine needs more fuel.....Cliff

[F250 Restorer]

I installed the rebuilt today.  Although I disconnected the choke, and the idle screw is all the way backed out, I can't get the idle to drop to normal.  First off I tried to adjust the mix, and there was no difference whether all the way in or out.  So I snipped off a rung of the springs, and now it starts to shutter when all the way in.  I assume I should snip off another bit?  The engine should die when all the way in, right?  Also, I'm guessing it is idling at about 1200 rpm, minimum, and surging.  When I try the 'tip in' it speeds up, so I think it is lean? 

Normally I would think vacuum leak with the idle staying up.  Tomorrow I will spray around the crab with starting fluid, and see if I have a leak. 

Help is GREATLY appreciated.

[F250 Restorer]

I also found this and wondered if someone could explain it:  Don't try to set the idle without holding the hot idle compensator tang back on the back of the carb.

[Cliff Ruggles]

I would block the HIC hole and not use it.  Just another potential vacuum leak at idle.

The engine should idle down, if not, too much idle bypass air, vacuum leak, secondary throttle plates not seated well in their bores, etc.

The mixture screws may not kill off the engine when seated, as some fuel is delivered thru the exposed portion of the idle transfer slots at idle speed.  Turn the screws in till it just slows the engine, back them up about 1/2-3/4 turns, should be pretty close for idle mixture settings.....Cliff

[F250 Restorer]

I finally got around to working on the carb again.  I emptied it, turned it over and could only see a line of light around the edge of the primary and secondary butterflies.  I was able to idle it down to eight-hundred rpm, took it for a drive, but got back and it was up to 1000 rpm.  

I noticed there is a slight ooze of fuel from the booster holes, just getting it wet.  I also noticed that when I manually push the throttle closed the idle drops 100 rpm.

Is it normal to have the fuel spray out when I disconnect the fuel line?  I've never seen that before.

I should also note that I sprayed around the base with starting fluid to no affect.

[F250 Restorer]

I loosened the s. flaps and played with then to get them positioned correctly.

All four butterflies look seated.  Still it idles at 1,000 rpm.  I can get it down to 800 rpm by screwing in mix a bit, but then it runs rough.  It also surges 100 rpm up and down.

[Cliff Ruggles]

It's got to be getting idle air from someplace.  If all 4 throttle plate are fully seated, the engine should stall out. 

Did you eliminate any idle bypass air in the baseplate?

Plugged the vacuum hole leading to the choke housing for the hot-air choke?

Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff

[F250 Restorer]

It's got to be getting idle air from someplace.  If all 4 throttle plate are fully seated, the engine should stall out.

Did you eliminate any idle bypass air in the baseplate?  If that wasn't mentioned in the book, then I did not do it.  How do I do it?

Plugged the vacuum hole leading to the choke housing for the hot-air choke?  I installed the housing from a latter model with elec. choke.  The v. hole does not continue through housing.

Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff  yes.

[F250 Restorer]

It's got to be getting idle air from someplace.  If all 4 throttle plate are fully seated, the engine should stall out.

Did you eliminate any idle bypass air in the baseplate?  If that wasn't mentioned in the book, then I did not do it.  How do I do it?

Plugged the vacuum hole leading to the choke housing for the hot-air choke?  I installed the housing from a latter model with elec. choke.  The v. hole does not continue through housing.

Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff  yes.

by the way, the carb # is: 17058504

[F250 Restorer]

I have the idle bypass in both the main body beside the boosters, and in the airhorn.  Should I plug one set of holes? 

[Cliff Ruggles]

I would make sure the vacuum supply hole to the choke housing is blocked in the main casting, even if you switched to an electric choke.

Make sure any idle bypass holes in the baseplate are blocked, no need to block them anywhere else.

Once you get full control of all the air entering the engine, you will have full control of the idle speed of the engine.....Cliff

[F250 Restorer]

Thanks, Cliff.  Since I'm sort of new to the QJ, can you please point out which holes to plug, and how to do it.

Thank you.

[Cliff Ruggles]

The two holes closest to the idle mixture screw tips, at 1 oclock and 11 oclock in the pic.  Best to tap them and install a small set screw, 8-32 or 10-32, then we can always install a drilled brass set screw later if needed....Cliff

[F250 Restorer]

Cliff:  Getting a tap in the right side bore is out of my ability.  I suppose I could take it to a machine shop, but at this point I am not willing to do that.  What I did was fill the hole with epoxy.  If I need to open a hole later for more idle bypass, or the nozzles are dribbling, then I can do that.  Right now I will reassemble and see how it does on my ford 300, with 250 hp.

All your help has been exceptionally valuable.