dirtydave289

Finally got this pony started and it was running like complete crap, wouldn't idle, put it in gear and it'd die, etc.

Timed it @ 8* BTDC for now, ran the mixture screws all the way in and out 1.5 turns, got new plugs/wires and attempted to tinker with the carb. Now she is idling in park/neutral/any gear, running decently down the road but she is studdering like all hell and hesitating if you blip the throttle or sometimes just under normal acceleration.

Carb ran fine like a year ago when I took it off the Mustang and put it on a truck I had. Sold the truck and put it back on the Mustang now it's not running worth a damn like it used to. Where to start? I know the problem lies somewhere in the adjustments (although I never changed them) because she's clean as a whistle and functions (valves etc) great. Just runs like crap! lol

Gun Jam

could be a weak fuel pump...could be a lot of things...

I guess take the fuel line off the carb and place it in a glass jar..crank the car over for 5 seconds and see if it fill the jar all the way up... if there is just a little puddle in the jar then its probably the pump

jojobanks

If the carb has been running good otherwise and you're confident it doesn't need a rebuild, possibly check that the throttle linkage is adjusted properly and that the carb gasket is good and not leaking anywhere.

Either way it does sound like a fuel issue.

Gun Jam

Jojo has a good point...also check for vac leaks by spraying carb cleaner around the base of the carb while the engine is running if the engine changes tune as you spray then there is a vac leak at that point.

Fogged propane can be used as well its less messy but requires a fair volume and some sort of a nozzle.

Either of these methods is a potential fire hazard take necessary precautions first.

-Gun

oldrock

another thing you could check is the timing curve. A quick and dirty way to test it is to just advance the timing a few degrees and see if it runs better. If it does, then you have narrowed down what is wrong. I helped a buddy install a rebuilt 289 in his 66 GT and we had an issue with the timing curve. Before fixing it, the car would accelerate like a 4 cylinder. Learned it was not getting anywhere near enough timing advance. After getting the timing issues sorted out, same engine would burn rubber off the line and accelerate hard from 0 to 60.

oxfordbp

Plugged fuel filter was my issue on my 2bbl. Just a thought. I would start with easiest first, check fuel pressure!

crunchyskippy

I would add: Check your accelerator pump. It could be that it's not functioning, or is not giving a large enough shot during acceleration. In turn, you're creating a temporary lean condition when the blades open.

What carb is it?

Good luck with a resolution.

dirtydave289

No leaks, fresh filter.

Now it's driving/idling pretty well but can't get rid of the tip-in stumble. If I hold 2-2.5k rpm's and blip it, no stumble. Yet if I blip it from idle (8-900 for now) it has a choke/stumble then revs up. Sometimes it just stumbles and othertimes it backfires and every now and then if I go wide up real quick from idle it'll spit a fireball out.

Got my mixture screws adjusted about 1.25-1.5 turns out - that's where they're pulling the most vacuum at idle. Timing is spot on. Just need to get this little stumble worked out. It's a 4150 with mechanical secondaries. I don't think it's secondary related because the stumble occurs under moderate throttle blips where the secondaries wouldn't even be open.

I appreciate all the help guys.

oldrock

have you experimented with opening up the mixture screws to see if that makes things better or worse? Sometimes you have to do some experimenting to get things all dialed in.

Re backfiring: first thing I check when I hear backfiring is to make sure the manifolds or headers are tightened down properly. If that is good, then I look for lean condition which opening up the mixture screws would be a good first step.

Gun Jam

If you checked the rest of the stuff now your description sounds like it could very well be timing.

Try advancing timing 3 deg... it may make a huge difference. Chances are doing this will eliminate that flat spot when starting off from a dead stop...

-Gun

P.S It may prove very useful to measure each exhaust header's temp. After a short run use an IR temp gun and see if the header temps are reasonably close...If you find one that is say 300F cooler than the rest that may help solve some problems too.