Spark plug tool

I recommend the wire type gauges, usually round with several measuring wires. I forgot the reason I was told its preferred but many years ago a Jag mechanic taught me to use one.

 

Surprisingly, the original tool really is about the best tool for the job ---- if you get creative, many other things will work, but I always prefer using the OE tool.

 

I have something like this that I picked up in the UK.

Performance Tool T-Handle Spark Plug Wrench — 5/8in., Model# W1129C | Spark Plug Tools| Northern Tool + Equipment

 

NGK BPR5ES. $2 and in stock at your local O'riellys. Change once a year they will be fine.

Also if you are changing plugs... It's a great time to run a compression test. I do it cold but some like it hot

Threading the rubber compression hose on the back bank, now that is a really good time!

 

Sean and Mule's posts reference a 5/8inch socket. NGK BPR5ES plugs take a 13/16ths socket. Is 5/8ths for a different plug?

 

Mule's car is a 328; the 3,2 engine has smaller-diameter spark plugs than the 3,0 litre, 12 mm versus 14 mm; this might explain that?

Rgds

 

The numbers got a little mangled in this thread, but neofer has the concept:

The 14mm thread F engine spark plugs (e.g., 3.0L) use a 13/16" hex drive

The 12mm thread F engine spark plugs (e.g., 3.2L) use an 18mm hex drive

There are some 14mm thread spark plugs that use a 5/8" hex drive, but these tend to be the gasketless tapered seat kind of spark plugs (had a couple of Ford 351 Cleveland that used them).

 

I posted that link as an example picture of the tool I have. The one I have fits my plugs, but I can't tell you off hand the exact size. My last major service says spark plug is part number 131927.

 

For reference and posterity

For my 1979 308 GTS North America

• PT Performance 13/16ths T-handle (https://www.amazon.com/dp/B000N35LZS) - too thick - 27.80mm od
• Powerbuilt 13/16ths 6pt magnetic (https://www.amazon.com/dp/B016SEIDZA) - says thin-wall. 27.73mm od. too thick
• Craftsman socket set from Ace HW (https://www.acehardware.com/departments/tools/hand-tools/sockets/2297232) - 27.76mm od . Maybe a classic craftsman would work but not the new ones.
• 21mm 3/8ths Socket (unmarked. not sure where I got it) - 27.60mm od - too thick
• Champion CT-407 13/16ths 6 PT socket 3/8ths drive off ebay (example: https://www.ebay.com/itm/234074036617) - 27.40mm od
  
• Briggs and Stratton Spark Plug Wrench (https://www.acehardware.com/departments/lawn-and-garden/lawn-mowers/lawn-mower-parts/7105851) - 26.00 od

Oddly, the CT-407 worked in cylinders 1, 2,4 but not cyl 3. That tube was slightly narrower. Has anyone else noticed that specific tube being narrower or is something else going on?
The Briggs and Stratton wrench is narrower but it's too long for cyl 3 unless I undo the torque bar connected to the valve cover

 

I have sourced a number of older Craftsman sockets that are thin (walled) enough!!

 

"Change once a year they will be fine."

Since a spark plug doesn't deteriorate with time, I'd use mileage as the replacement guide. The 328 owners manual says 30,000 miles. For most owners that probably means that when you change the plugs the first time, it's also the last time.