Rough running 318

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James Kelly

James Kelly

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Apr 3, 2019
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Peoria, Il
My 318 recently started popping out the exhaust while idling in park, and when I put it into gear it barely idles at all. I tried driving it around, and it will not rev at all, it sounds like its misfiring every other cylinder. The engine has a double roller timing chain that I installed last summer, and im certain it was installed correctly. I put a vacuum gauge on a full manifold port and it reads steady while idling in park at around 24hg. when i put the car into drive it stumbles and acts like it wants to stall out. While in the drivers seat it almost sounds like a knocking/grinding noise coming from the floor, but in the engine bay it sounds pretty normal. I even my a socket extension on the valve cover and held my ear on it to make sure there wasn't any internal knocking. I pulled the valve covers to make sure all the rockers where moving, and they were all normal. I had just had the heads machined last winter. every cylinder was within 3 psi of 120. I have the initial timing set at 18* with a FBO lockout plate inside the distributor, and the total timing is around 32*. I pulled the plugs they are all optimal except for 1 which was a little bit darker, but didnt look like it was dark enough to cause any issues.

Here is 3 videos put together, the 1st is it idling in park while its warm, the second is after I tried to drive it around, and I put it into gear, and the 3rd is in gear with the parking brake on. The idle is high becuase it wont run in dirve without the idle being jacked up a bit.


Thanks to anyone who can help, i'm 19 and i'm trying to learn and do all this by myself, i'm the only car guy in my family.
 
Lets start by checking two things. Engine off- pull distributor cap off and inspect rotor, is it solidly in place with no obvious damage? Look at the underside of the cap- are all nine of the contacts OK? Look for "carbon tracks", little dark marks/lines (look like cracks) that are really voltage arcing to ground. Replace the cap and re-confirm that the plug wires are properly routed. If all is good let's go to engine running. Start the engine and idle it down to where the engine just runs. Take off the air cleaner. Put your hand over the carb blocking 80* of the air flow. With the engine now starving for air (running rich) does the engine RPM now speed up? If it does speed up, this indicates that the engine is normally running lean and we have a carb/fuel issue or a vacuum leak. If manually choking the engine doesn't speed it up (but now wants to die), we have eliminated that possibility.
 
James, usually popping through the exhaust is almost always a lean mixture. I would check to see it's getting adequate fuel supply. Make sure the fuel pump is working properly, check to see the fuel filter isn't stopped up. What kind of carburetor?
 
So i tried richening up the mixture screws and idled it down to 900. It runs and doesnt act like it wants to die. Before i made it richer, i used the manual choke to see if it was running lean, and choke off the air just made it want to stall out. I drove it around after I got the idle stable, and its alot better. Now it pops out the exhuast right before it shifts. Other than that it sounds like its running on all cylinders, and i sprayed a little bit of water on each header tube to make sure it boiled off. The cap and rotor are really clean. I also found a spark plug boot that was torn on the dis cap.

The carb is a 1406 650 cfm with a manual choke, and I blocked off the little vacuum port hole where the electric choke was. I blew threw the fuel filter and it didn't have any restrictions.
 
Sounds like you are on the right track. Maybe you need a little practice carb adjusting. Congrats!
 
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