1994 348 spark plug socket

355 is a 5/8 socket. Not sure if 348 is the same

 

16mm for both cars.

 

According to an NGK reseller, it's 5/8 which is the spark plug socket I use (355)

But 5/8" is .625 and 16mm is .629 so given the tolerance they both must work.
Image Unavailable, Please Login

 

Please note - what I posted above is for the 355. I went to the NGK site and for the 355 it lists different P/N's, states 5/8 hex but for 348 it does state an 18mm hex.
Image Unavailable, Please Login

 

OK, It has been 6 months since I pulled the engine on my 348, and I cannot be exactly sure whether it is 18mm or 16mm. But, I am sure ONE of those will work.

If it does not, then there is something sitting at the bottom of the hole that prevents the socket from dropping down all the way to engage the flat parts of the plug.

Can you tell that it has happened to me before?

 

It's 18mm.

I had to buy a 18mm deep socket for it, because I only had 16mm.