454 problems timing/carb?

Hello everyone, new guy here. Ill cut to the chase. Having issues with 454. Bought the truck 73 4x4 chevy etc. Had an old rochester carb on it. As far as know motor is completely stock besides headers. Bought the truck drove it home, ran fine for a few days then like a week later i was driving and the truck starting running extremely crappy. Like misfiring and backfiring. Pulled over, popped hood and fuel was all over the carb. Let it sit for a minute and fired it up, ran like crap all the way to my house. Pulled the carb went through it put it back on and still ran like crap like wont even idle. Misfiring, back firing, wont idle, barely starts, wreaks of fuel. Checked cap and rotor ( hei) cap was good but rotor had the metal piece on the tip broke off. Replaced both and wires, still running extremely poor. Firing order is correct on the wires. So went back to fuel issue. Bought brand new carb quikfuel 670. Still running really bad. Misfiring backfiring, sounds like a lopey cam and smell fuel pretty bad, It has a mechanical fuel pump, checked that out, everything ok there. Pulled distributor checked it all out. Seems ok. Put it back, put another carb on it, still running horrible, cant even drive it wont idle sounds like a lopey cam even tho its stock Misfiring etc. All vacuum hoses are correct. Spark plugs were black as hell. Changed those, double checked everything, cannot for the life of me figure it out. What should i do, im at a loss oh also took valve cover off disconnected ignition and had friend turn it over and all valves work good. Help lol thankyou for reading all of that, any help would greatly be appreciated

Does it crank evenly if ignition is disabled? If not do a compression check.

Install a vacuum gauge is it steady, what is the reading?

Check fuel pressure

Run compression. Check for slop in the timing chain. Check the timing chain while you are doing compression. All plugs out,dist cap off turn the engine counter clockwise and clockwise see how far the crank moves,before the distributor rotor moves. Only seen timing jump 1 tooth in my life,but I wouldn't rule it out from what you are describing. Actually the one time I saw it,is a funny story. I was working on the car,told the know it all shop owner,what I thought. He said, come on when have ever seen timing jump 1 tooth and keep running? I said never,but it's the only thing that makes since. He said go ahead,in a that's a waste of time tone. But that was the problem.

Thankyou, ill check the compression today and get back to ya. And also ill check the chain slop, ill keep you posted, thankyou for the advice. Im determined to get this thing goin

Did compression test 140 to 150 on all cylinders, fuel pressure is 5psi and vacuum is steady, just an update.

With those numbers I don't suspect the timing chain,anymore but check it anyway. No plugs in roll the engine over clockwise with a breaker bar 2 turns and then to the middle of the time scale. Now turn the engine counter clockwise and watch the distributor rotor,the milli second it starts to move stop turning the engine and look at your timing scale. The degrees you rotated before you got movement is slop. It might be better if you had a friend turn it while you push the rotor down with 1 finger and feel when it moves. Anyway post your number.

mxnocean said:

Did compression test 140 to 150 on all cylinders, fuel pressure is 5psi and vacuum is steady, just an update.

Click to expand...

Vacuum is steady. But what reading?

Is your distributor vacuum advance cannister working and connected to manifold vacuum. Not ported vacuum?

Checked for timing slop, rotated the motor lightly to check if dizzy had play from clockwise to to counter clock wise, everything is tight. And vacuum advance is to the carb and the reading is 16hg acording the gauge plus or minus 1hg

Good vacuum, good compression. Timing? Carb adjustment? Fuel filter(s)?