Ok, I am gonna try this again. First, i dont have or will buy a 4 bbl carb. My truck came from the factory with a 2bbl. I have a bone stock 400 ci with a performer intake manfold and a holley 4412 2bbl 500 cfm carb with a manuel choke. i dont have headers or anything after market eccept for the intake manifold.

I have completely rebuilt this carb, maticulously cleaned it and I seem to have a really bad hesitation upon acceleration almost choking itself out. I have gone back and forth adjusting the idle air and the acclerator pump arm and the float and i cannot seem to get rid of the hesitation. I have double and tripple checked for vaccum leaks and there are none. I do not have the $$$$ to just simply replace it keep putting cash into it. I just need some serious advice. I do applologize if i sound like i am going on about this but i did try this once and all i got was "put a 4 bbl on it" or "its a holley". That stuff doesnt help me at all.

anyone have any ideas?????

 

I believe the 4412 carburetor is more suited for racing/dirt tracking.

Myself, I much prefer the Holley 2300.

 

see, this is why i try to use this site as a last resort, i didnt ask what you prefer. i asked for help

 

You could try upping the fuel squirter size to help eliminate the hesitation you are seeing.

They are stamped with a size number try going a 2-3 sizes larger.

 

you think its a lack of fuel on the hesition?

 

You could try setting the choke some & see if it still does it.
I do agree with Jermafenser. The 500 is way too big for your motor. Even if you can get it to work it will run rich & use a ton of fuel. Been there done that. Bought the 350 model, set the screws and never touched it again.

 

Perhaps the stumble is timing, and not the carb?

 

Just my two cents, but in my experience a hesitation like you are experiencing is caused by too much fuel. I don't know your elevation, but I live in denver and i had to change out my metering rods and jets to get my truck to run correct. I don't think timing will do this to you, it will either be a dog or it will ping depending on which end of the spectrum your at. Is it backfiring? Another thing, I don't have your carb but maybe a similarity, I had my vacuum advance hooked up to the wrong port as the edelbrock has two, this was causing me to go to full advance almost immediately and I had a problem similar to what you discribe, but as I say it was also backfiring out the carb.

 

You may need to go to a smaller accelerator pump squirter. As I recall, the 4412 comes with a 50cc accelerator pump, way more than your stock engine will ever need. Have you changed the main jets? I think that carb comes with #72 or #74 mains, that may be a little fat for your engine also.
FWIW, I used to have a 78 F250 with a stock 400 exept for a 4412 Holley, it worked great for me, more power than the stock carb. It's been a few years so I can't remember how I had it jetted.

 

Uhm...

I WAS helping you. I'm saying the 4412 is NOT the best carburetor for your application.

Jesus.

 

Its either lack of or too much about 90% of the time it is lack of fuel that causes an off idle hesitation.I would also check your ignition timing it could also be a culprit It wouldn't hurt to try bumping it 2* at a time to see if ther eis any improvement.

 

I appologize for being short with you. I hav tried to ask for help on this matter befor and all i got was guys telling me to just replace it with somthing bigger. Again i do appologize and thank you for the help.

 

do you happen to know what the stock 2bbl that came on this was rated, as far as cfm wise? the 4412 came with 73's. i went to a local parts store that a very good holley parts selection and the local holley nut told me to run 68 jets and a 55 power valve then reset the timing to 8 btc. done all but reset the timing, hesitation is gone but top end is weak

 

I'd try a couple of 70's and see if that helps your top end, its cheap and easy attempt anyway, anytime you use something a bit different you will have to tweak them some until you get it right..

 

I'm pretty sure the carb in question in the original post is a 2 bbl street carb ,model 2300, part number 4412.

Here's a link to it Holley Performance Two Barrel Street Products

I'm running this exact carb on my 390 and it performs like a champ...

Maybe install a pressure gauge right before the carb, just to make sure the fuel pressure looks allright, should be around 5 to 6 psi.
Also, try pulling a few spark plugs to see how the engine is running, I'm sure you know this but black is rich and white is lean...this might help you narrow it down?

If you have a Haynes manual, it describes a really good way to check and see if the fuel pump is delivering the proper volume of fuel to the carb...it does sound like it could be fuel starvation; maybe your fuel pump is in need of replacing?? Good luck man!