Inliners International Forums General Discussion Engines Spark Plugs Types for 194 - 292 L6

Hi All,

I have quite a few heads for 194 - 292 L6 motors. I have noticed that they use different types of spark plugs. The head I am currently working on appeared to use Autolite 404 plugs, but they do not tighten down into the hole correctly. Another 292 head I have used real skinny plugs. Does anyone know the details of the different plug types used in these heads?

The 404 is a OLD autolite plug which is a 13/16 plug which has a compression ring at the base. The skinny plug is a 5/8 plug with a tappered seat.

The head I am working on now, the Autolite 404's compression ring comes no where near to seating. The clearance hole is too small. So there is a 5/8" still that show be the right one to use? Any part numbers? I usually have to give my local parts guy a specific year for a part in order to locate it.

The other head I was referencing with the super skinny plugs used a smaller diameter thread size and i used a deep 17mm socket to get it out. Those plugs won't fit the other head what-so-ever.

well first off NONE of the L6 heads use a mm at all.Back then everything SAE. I'll have to dig up some of my Old plugs.If you can give me the casting numbers off the plugs.This make things easier.

Yeah they have the deeper socket, I use AC R45LTSM.

Yeah they have the deeper socket, I use AC R45LTSM.

Thanks for the input. I used the 17mm deep 6 point socket cause it was the only tool I had that would get at it.

Ok, I got a set of AC R44LTSM plugs and they worked great! The 5/8 plug socket I was using had too thick of a side wall. I used a different one I had and it worked fine.

Yup R44 is what they call for, I use a one step hotter plug, glad ya got it going!