440, acting strange

[Paul G]

A friend brought his car over to figure out what was going on with the engine. He has owned it for a year, so no back story on the engine build. It was running good, till it wasnt. The engine started to run rough and die.

It is a 440 with a little more cam than stock. Iron heads and headers. Low rise intake with an Edelbrock carb. Stock type Mopar electronic ignition.

We raised the idle to keep it running, went around the distributor pulling one plug wire at a time. Cylinders 3,8,2,5, had little, little effect when the wire lifted off the cap. The rest of the cylinders had a pronounced effect on idle when the wire was lifted off the cap. They are a nice set of wires, no visible burns, cracks, or other problems.

We pulled all the plugs. NGK V-Power plugs, and found them gapped at .070", too wide. Nice light brown color. We regapped them to .035". Restarted the engine, adjusted fuel mixture and idle speed, which helped smooth out the idle, Went around the cap again with the same result. 3,8,2,5, having little effect, the rest having pronounced effect on idle. Set idle speed and it is running again with out dying. Hmm?

I am going to do a compression test. Other than that? The engine sounds like it has a roller cam or at least rockers, noisy valve train. Do not know at this point till I pull a valve cover.

[c00nhunterjoe]

Compression test before you pull the covers. All plugs are even to include the 4 weak ones?

[BSB67]

If it is a dual plane intake with divider, I believe that those 4 cylinders are feed from one side of the carb.

If that is true, rebuild the carb, new plies and try again.

[c00nhunterjoe]

If it is a dual plane intake with divider, I believe that those 4 cylinders are feed from one side of the carb.

If that is true, rebuild the carb, new plies and try again.

Good point. Didnt think of that. I would still investigate why the valvetrain got noisey

[Paul G]

If it is a dual plane intake with divider, I believe that those 4 cylinders are feed from one side of the carb.

If that is true, rebuild the carb, new plies and try again.

I did not think of that. Thank you. I will check and see if those cylinders are fed from the same side of the carb.

[Paul G]

Spot on you are!

Started the car up today and after warm up it was idling high, around 1300RPM. It was set at 900 on Saturday and had been sitting since. Took it around the block and it was running fine. Set idle back down to 900 again. Running great.

The cylinders in question are all on the right bank of the carb. I went around the distributer lifting each wire, and each cylinder had the same effect on idle. The problem being in the carb is highly suspected at this point. The owner wants to switch over to Holley now.

[c00nhunterjoe]

Russ for the win. Nice call.