Greetings. 1985 5.7. Backfires through the carb during acceleration. Dies when I hammer it. Please tell me E-X-A-C-T-L-Y what I need to check. If there are 100 things that I need to look for, please tell me ALL 100!!! I'll print it out and use it as a checklist. If you need more info from me, please ask!!! This rig is my daily that I'm on the fence on as to spending the money to fix or sending it to the heart of the internet Bermuda Triangle known as Craigslist. Thanks!!!

 

check timing, i had an issue with the stock carburetor the secondaries would not open causing it to die when giving it a lot of throttle

 

Usually a backfire through the carb is a timing issue.

Usually. I'd look there first.

 

Well first off when did back fire start .Did you do something to the engine ? i say backfire is caused by lean fuel condition . Such as dirt in the carburetor . Could be low fuel pump pressure . Look down in carburetor and operate the throttle and look for a strong stream of gas . have you changed your fuel filter ? Those small filters clog really easy !!!!

 

Bought the thing about a month ago, missing a few parts (air filter, breather filter, pcv valve, fuel cap, o2 sensor, coolant resorvoir, other non engine-related parts). Replaced those. It needs a cat and muffler (previous owners cut the old cat off and clamped it back on with tubing sleeves after they were told it would need a new cat to pass smog). Ran good-i.e.,no backfiring-before I started replacing parts. Sprayed the carb. It wants to die when I spray the front. Accelerates a little when I spray into the rear. Vacuum lines are intact. I pulled the screws out and sprayed inside. Passenger side was clean, driver side had a little black gunk come out. I have them both out about 3 turns. Cap, wires, plugs and firing order are on the agenda tomorrow...4 slices of combo pizza, 3 large garlic sticks, all u can eat salad and about 5 beers DOES NOT equal pop the hood and lets fix the problem tonight...

 

I think it's time fro a rebuild kit . You could have disloged dirt in the jets . Another trick is to spray carb cleaner down the vent pipe . Rev it pretty fast and close the choke until it almost dies then let open back up . This will suck the dirt out of the jets . May work ?