What plugs do I use now?

[MR nova @#25]

I have a pair of newly Rebuilt Ford 302 motors, with 4bbl carbs and pertronix distributors. Whats plugs and gap should I use

Thanks

 

[achris]

Same as spec...

 

[MR nova @#25]

The new heads on the block are 351. The plugs listed in one of the Mercruiser sites, list Part# 33813425.this plug is to small diameter.

 

[achris]

There are 2 common plug thread sizes. 18mm, which normally have a compression gasket as part of the plug (see below picture #1), and the head has a 'square' seat. And 14mm which is a tapered seat plug (picture #2). When Mercruiser were using the Ford engines, they were also both heads around, often at the same time. :facepalm:

If the head has 14mm tapered seat holes, the right plug should be AC-MR43T (NGK BR6FS). If the head has square seat 18mm holes, then it should be AC-CR83T (NGK AR6FS)...

The gap should be 0.76mm for either plug.

Chris..........


Picture #1 (18mm plugs with compression gasket)



Picture #2 (14mm plug with tapered seat)