302 running prob

[metallica21156]

i have a 71 302 in a mustang with a auto tranny. the motor has a 2 bbl carb with a 4 bbl intake. everything else is stock. i'm having problems getting it tuned right. if i advance the spark then when you smash the gas it revs right up but if you hold it at 1,500 or high it misses really bad and gets worse as it goes higher. if i retard the timeing then it can run rpms higher with out missing but when you smash the gas the engine will either die or almost die and then rev up. its got the autolite 2100 on it and it was rebuilt about a month ago. i just did a tune up last week and didn't make a diff. i'm running mid grade in it to see if it did anything. i also tried playing around with the mixture and didn't seem to make that much of a diff. any help would be nice.

[Kathmandu]

Did you, by chance change the cam when you changed the intake and carb? If you didn't then you aren't likely going to get the right mixture no matter what you do. I'm no expert but I tried this years ago and ran into the same problem.

[metallica21156]

no change on cam. the only thing with the intake is the manifold. everything else is stock. the manifold is off a mustang cobra. its a high rise and its the more expensive one you can get. i took it to a shop that i know and we checked the timing and it was dead on. the accerator pump was a little off i think. it was set to the highest mark. now when you rev the engine from a idel it will shoot fire out the carb and pop real loud but the engine keeps running. i'm going to duble check the float level tomarrow. any one know off hand what its supposed to be at? later this week were going to check the fuel pressure to make sure thats not causing it. it still has the problem of after it hits 3,000 rpm it starts missing real bad and you can feel the loss of power. any other ideas? would putting a 4 bbl carb fix it with out a cam?

[Kathmandu]

Ok, I missread, you still have the 2 bbl on the car, just a 4bbl intake manifold?If you have fire coming into the intake then you may have a valve problem. Did you change the intake yourself? Double check your spark plug wiring, I had a Camero once that had a similar set of symptoms and it ended up being a swithced set of wires. Garage I took it too didn't find the problem, I eventually discovered the error myself.

[metallica21156]

i had pulled all the wires off when i did my tune up so i didn't know where they went so i looked it up one the web and got the wiring. i forgot to metion that when we pulled the #1 plug it was clean like it wasn't even firing. we checked others and same result. i didn't change the manifold it was done when i got the car. i had the same problem with fire shooting out before i rebuilt the carb. if u have a pic i'll check to be sure. theres a #1 marked on the cap so i know that ones right. and the rotor lines up with it when #1 is at btdc.