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rough running 454

it should have a 750cfm carb on it from the factory and the truck is from this altitude so it should be jetted properly, but i havent torn the carb apart thats on the motor. the extra carb is dissasymbled and sitting in my room right now, looks rebuildable but i've dealt more with diesels than gas so its a little new to me.


i replaced the fuel filter and fired it up today. was running good at idle again but if i used the skinny pedal to accelerate it would still backfire. so i climbed under the hood and slowly throttled up and turned the distributor cap by hand clockwise as i raised the rpm's. for the most part it seemed happier, wasnt back firing near as often or as hard but had an occasional backfire that was intermittent. brought it back to idle while rotating cap cc with similar effect. thinking that with the new fuel filter (old one was almost black) that it can drink enough fuel now, but maybe its just the vacuum advance on the distributor? could just the vacuum advance be replaced on a stock distributor or would i have to buy a whole new dizzy?

new carb would be nice but since i already have a spare quadrajet carb i would be money ahead to just rebuild that one and swap them out.
 
found the distributor problem! looked at the parts underneath the rotor, where the 2 little springs are and they were rusted in place. cleaned them up, got some stronger springs and now the truck runs good as long as i keep it at 1000rpm's or higher. if i let off the skinny pedal idle drops to around 300-400 rpm's and has a big lope to it that stalls it out. think maybe not enough fuel flowing?
 
Back fire is timing issues, Poppin through the carb is Valve train. Rough running is usualy caused by timing but BBC's are know for valve train destruction, check the compression it will give away if you have a vavle issue quickly, the numbers will be very different in the messed up area.
 
You might need a cam. Whats your total ignition timing with vacuum advance disconnected?
 
sorry havent checked this thread in awhile. got the issue solved, dizzy had a broken tooth on the gear so had to replace it and the carb was all screwed up internally. will need a new carb but since i'm flying to iraq tonight a new carb is gonna have to wait until august.
 
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