Rough running 427
 

Recently on my weekend drive my 69 427 started running rough. After warm up the engine will not idle without me feathering the throttle and runs rough. I’ve had an issue in the past of an ignition wire backing off a plug. How do I ensure the wires stay fully seated on the plugs. I have the wires with the metal braiding.

Ive also recently pulled the distributor to repair the tach gear. Car had been running good until recently.

Any thoughts on what could be causing this condition?

Did you replace the vacuum line on the vacuum advance can? It sounds like you have a vacuum leak. That would normally be due to a vacuum line being left off by mistake.

Pulling the suppression wires off the plugs or just old age can sometimes break the internal carbon. Remove one wire at a time & check the OHMS resistance. Most are about 5,000. But check what yours are supposed to be. At the least, it will tell you if the wires are good. Also, I'd remove the plug from the wire that fell off & confirm that it was not fouled when there was no spark going to it.
Think small stuff first.

Google ohmeter.

It is very simple once you buy an inexpensive digital ohm meter. ( will probably be a "multi meter" that can measure several electrical functions ) Set it to "ohms" in the 20,000 range; connect one contact to each end of the plug wire & the meter will read ohms. OHMS are a measure of resistance & cars in the last 30+ years have required "resistance " plug wires to eliminate interference in radios & other electrical devices. Anything over 6-7,000 ohms is questionable. If there is an actual break in the internal carbon, the meter will read "zero" and, thus, no spark.
Please let us know what you discover.

What did you discover was the problem ? And how to you resolve ?

M.i.a. .....