I recently acquired a 86 f350 duallie with a 460 engine. I runs pretty good at idle(a lil rough....sat for 2 years). Problem is when I put it in drive and apply the gas it stutters. It has the cali smog stuff so im getting ready to pull that and the cat out. It has new plug and we just rebuilt the carb. anyone got anymore suggestions?

 

What, exactly, are you planning to do there?

A 1986 460 with a carb, is it a feedback carb?

 

I'm interested in what the "Cali smog stuff" is? My Non-Catalyst 460 has a non-feedback Holley 4V carb, two air-pumps, EGR and evaporative vapor canister setup. I was thinking this is standard equipment for 460’s built before ’87.

BTW, you should spend some time troubleshooting and determine what is and is not working before pulling and trashing engine components; get a hold of a manual. In the end you will save $$ and fix the problem sooner. There's a lot here, but you should verify the basics first: confirm that fuel pressure and ignition coil/wires are good and engine has proper compression. Is the carb working properly now, can you test it on another engine? Did rebuilding the carb change anything (better or worse)? What did the inside of the float bowls look like, any tan powder in there? I've seen my share of carbs screwed up by rusted gas tanks. We will need a better description of the symptoms and a summary of troubleshooting you’ve performed.

 

bern, I believe I have the same setup as you. Before the rebuild it still had the same problem. Were getting a new carb ordered friday...just to cover all the bases. It does seem like the catalytic converter is plugged though the way it is running. The coil and wires are fine along with the new plugs. Only thing I didnt check was the rotor but I figure its gonna be fine as we are still getting good burn at the plugs. Inside of the bowls revealed the typical laquer that u would expect but no rust. Biggest problem Im having is if you put it in gear it feels like it is falling on its face when you accelerate.

 

Sounds like a bad accelerator pump to me. Or the passages for it are blocked.

 

Stosh has a point. The accelerator pump has a rubber diaphragm, 2 check valves, a discharge nozzle and lots of small passages for fuel to travel thru. run the engine for a few minutes, stop it and take the air-cleaner off. Look down the primary venturies and work the throttle, you should see fuel stream shooting toward the booster. If not, start looking for the clog. An obstruction in this fuel circuit will always cause an off-idle stumble.

 

ok can i get more info on this accelerator pump?

 

^^^ Read what Bern_F150_4X4 said ^^^

 

Well put a new holley avenger series on the truck tonight and rerouted the smog stuff and she runs great. It still stutters a lil if I just give it a lil gas but im thinking it might be a back pressure problem as it sounds like I have a exhaust leak somewhere.

 

maybe the egr is stuck open allowing exhaust gasses into the intake manifold.

 

is that the valve behind the carburator?

 

-------------------
Yes.
-------------------

 

since ive already removed the smog pump and associated lines....could I just cap off the egr valve?

 

The EGR is far different from the AIR system.
If you disable the EGR you will need to retune the engine to compensate.

Yes, it is the valve behind the carburetor.



If you hear an exhaust sound you can't locate check the exhaust crossover at the back of the cylinder heads.






.

 

how out of tune will it be? Im guessing it will run richer