SBC Help needed

[fzr400guy]

Well everything has been running great then all of the sudden a week ago it started acting like it was was misfiring while under load. I checked all the plug wires, and replaced all the spark plugs and the issue is persisting. I have determined its firing on all 8 so I'm thinking its either the timing went nuts somehow or maybe its an issue with the quadrajet carb. Any other suggestion or help will be greatly appreciated.

Engine specs:
Gen 1 350 crate motor. Stock
Quadrajet carb
MSD 6A ignition
MSD Street Pro-Billet w/Vacuum Advance Distributor

What I have done:
Replaced plugs.
Checked all plug wires.
Checked all the fluids.
Cleaned the distributor cap and rotor with a wire brush.

What I have not done:
Replaced the distributor cap and rotor.
Cleaned the carb.

 

[TallCanDan]

Possibly a hairline crack in the distributor cap, or dirty contacts under the cap as well as the tip of the rotor. Fine grit sand paper can remedy this. I have a carbureted SBC in my Blazer. After I replaced all the hard line going from the tank to the carb, small particles of rust were getting by the fuel filter, so I thought. I had two on there at the time. I would pull the two adjustment screws out, shoot carb cleaner in, reinstall the screws and it would be fine for only a short period of time. Then she would start sputtering again. Time after time I did this, and I finally took the carb off and in the fuel bowls there was the rust particles that had gotten by the filters before replacing the hard line, sitting in there. Cleaned it all out, reinstalled, she has ran fine ever since. Good luck,
HTH
-Danny

 

[fzr400guy]

Possibly a hairline crack in the distributor cap, or dirty contacts under the cap as well as the tip of the rotor. Fine grit sand paper can remedy this. I have a carbureted SBC in my Blazer. After I replaced all the hard line going from the tank to the carb, small particles of rust were getting by the fuel filter, so I thought. I had two on there at the time. I would pull the two adjustment screws out, shoot carb cleaner in, reinstall the screws and it would be fine for only a short period of time. Then she would start sputtering again. Time after time I did this, and I finally took the carb off and in the fuel bowls there was the rust particles that had gotten by the filters before replacing the hard line, sitting in there. Cleaned it all out, reinstalled, she has ran fine ever since. Good luck,
HTH
-Danny

Well I sprayed the heck out of my carb with Seafoam and mixed in a full can of Seafoam when I filled my tank this morning, and sure enough after a quick trip down to National City via the 94 and 805 freeway its all back to normal.

Thanks for the carb advise Danny.