Which spark plug number?

[fastempo]

I have a GM 140 4-cyl, ser no. 3463059. The manual calls for AC-CR44N, so I looked up the NGK conversion and bought NGK-BR6ES, but they have too large a hex-head, as you can't fit a 13/16"-socket in the spark plug slot on the engine. The previous plugs that were in the engine were NGK-YR5, and their hex uses a 5/8"-socket, which fits.
But I have not found any cross-reference of the YR5 plug to the 140 engine, so I thought I be smart and buy the BR6ES here from iboats---well wrong. Can anyone help me and set me straight, as I'm obviously quite confused about this. Thanks

 

[Alumarine]

Re: Which spark plug number?

I have a slightly newer engine and use NGK BR6FS or AC R43T (which are tapered).
These use a 5/8" socket.

 

[Don S]

Re: Which spark plug number?

Look at the head where the spark plug goes, does it have a tapered seat or a flat seat. Both types were used in that era. If you have the tapered, you need the AC-R43T or the NGK

 

[fastempo]

Re: Which spark plug number?

Thank you both so much, Don S and marc c.
UW

 

[fastempo]

Re: Which spark plug number?

Back again; in closing; I have the tapered seat, and I bought the NGK BR6FS tonite, at O'Reilly's automotive parts, and they were
only $2.49 each. Thanks for your help
UW