Re: 51 patrician spark plugs

Posted by JWL On 2012/2/26 11:52:06

This discussion thread, and previous ones dealing with spark plug heat range have reminded me of another factor to keep in mind. Problems are created by using the wrong reach spark plugs. Reach is the length of the threaded part of the plug. I forget the reach specs, but for the sake of conversation let's say for a 14mm plug of the proper heat range they come in 3/8" and 7/16" reach versions.

Using a 3/8" reach plug where a 7/16" plug is required will result in the bottom threads of the spark plug hole becoming clogged with carbon deposits. No problem until one tries to screw in the proper reach plug. The plug may not be able to be installed and damage to threads on plug or head may result. Running a tap into the hole will clean up the treads.

Using a 7/16" reach plug where a 3/8" plug is required will result in the bottom threads of the spark plug becoming clogged with carbon deposits. Problems occur when one tries to remove the plug. The carbon clogged bottom threads will prevent the plug from being removed and will cause damage to the threads of the plug and head. This may require removal of the head to repair the damaged spark plug hole threads.

Be careful in selecting the correct heat range, reach, and type (resistor/non-resistor) spark plug. The spark plug you remove and try to match may not be the correct one. Refer to a chart for the correct application. Brand is not important. Also, extended or protruding electrode type plugs should not be used in our flathead Packards.

Some Packards use the small 10mm spark plug, and some V-8 Packards use a 14mm plug with an extra long reach. These are special discussion topics, and not covered here. Others here may wish to add to this topic, and their contributions or comments are welcome. Thank you.

(o[]o)