Re: Spark Plug Torque

Posted by Ross On 2015/9/3 12:01:23

Just to comment a bit: I always used to do up my plugs just barely tight, like we did on tired tractors on the farm growing up. Flipping through a Nash service publication I was surprised to see almost two pages devoted to this subject.

Their chief thrust was that poorly tightened plugs do not conduct the heat away as they should and a loose plug will run much hotter than its heat range suggests. This is even worse if there is any blowby past the threads as it will heat the plug up like a blowtorch. Expect missing at that point.

A chronic pinging problem that I had for years in one car went away with the application of 20 lb-ft torque. I had occasion to run it fast and hard in traffic the other day in mid-nineties heat and never heard a single ping in 180 miles of less than pleasant driving.