Packard Forum Index » Pre-War (1899-1942)

I prefer to tighten spark plugs with a torque wrench.
Does anyone know what torque value should be used for a 10mm spark plug?

--Scott

See chart, courtesy of the AC Spark Plug Division. Note the comment that the values are maximum.

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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.

I'm going to change plugs soon in Best Other. I will use a torque wrench for the first time to tighten plugs. Never too old to learn.

Plugs on the 359 loosen up so I would definitely use a torque wrench.

An aid is to look at a picture of the 10 mm spark plug wrench supplied in some of the tool kits. It is a sheet metal housing with a cross shaft for thumb and index finger.

12 lbs ft actually seems a little high for those plugs, but the manual says 10-14.

Good discussion and advice given above. I would like to add that it is always a good practice to use new gaskets when re-installing spark plugs.

(o{}o)

It might to useful to convert these specs to inch/lbs too for those using torque wrenches so calibrated.

Just take the foot lbs and multiply them by 12 to get inch lbs