Turnbull

Alright guys i have a 1974 d200 with 1978 318 that my dad and i put in it it had low miles but we rebuilt it anyways by putting a 340 duster cam in it with 360 valves and 360 springs. We also port and polished the heads it has a 360 intake with a 600cfm eldebrock 4 barrel with hooker headers. But it has been sitting about a year and i fired it up started first crank but it spits through the carb and back fires at idle with about a 3 to 5 second pause between the pause. Need help!! Any answers will be very much appriecated thanks

Coronet 500

Welcome.

Have you had it running long enough to get warm? It sounds like fuel, too much = choke stuck closed, not enough = sitting gas has gummed up in the bowl.

I would look at these first before ignition timing, but have a look under the cap for corrosion.

440roadrunner

You............have...........a...........valve... .......stuck..........open...................

Or something similar.

do whatever is easiest first

Check the plugs

Run a compression test

Run a leakdown test

Get a grounded probe. Loosen the plug wires at the cap so you can pull them out one at a time. Pull each wire out and replace it with the ground probe See which cylinder(s) are not making power by observing engine sound and a tach. Each cylinder should drop equally

Pull the valve covers and inspect the valve gear.

Crank it over an observe the valves, do they all work?

Either bring each cylinder to TDC with valves closed........which means you must mark the crank balancer every 90 degrees. ....... or else pull the rocker shafts loose. This will close all valves. Inject air into each spark hole with an adapter fitting (or the one off your compression gauge) and listen for air.....in the intake......in the exhaust.......with radiator cap removed.........and in the crank case breather.

Turnbull

Thanks alot i will check it out and get back with you all to let u know the results

Turnbull

Alright guys so i did what yall said to try and when i pulled the carb off the gas was brown and also it had some seeds in it from the trees. Just one small one but then i looked in the bowl and it was pretty dirty looked like rust almost which makes sense cause the fuel gauge doesnt work so if the sending unit is rusted in there in could get to the carb right? While my one carb was off i put my other one that was perfectly fine and clean and started it up and it blew a spark plug in the 8 cylinder this is the second one now first didt think anying of it but i took one out of my 87 and put it in my 74 and it cracked it. Any sugesstions??? I apoligize for his being so long just tryin to get good results

Turnbull

I have been trying to find a solution to why my 318 is back firing but still nothing. Now its not blowing spark plugs. It might be cause i took the valve cover off and hit the valves with a hammer to try to unstick it. Then i also changed the ballace resistor be cause the other one was cracked. It isnt backfiring when when i give it some gas but dies if i let off. I dont kno what else it could be? Maybe it jumped timing i am not a mechanic. Thats why i am trying to get help from some mopar guys

Coronet 500

Could you explain "blowing spark plugs" to me?

Sounds like you have fuel delivery, carb settings problem still.

You may need to clean or replace fuel tank and lines, common to older vehicles.

If it clogged one carb it may have done the same to the other. I would check carb and clean if necessary then run fuel hose from pump into clean gas can to set idle mixture and timing to be sure it will run properly without possible debris from tank and lines.

This may give you the answer. If your not a mechanic, please don't hit valves with a hammer.