Spark Plug reach into head - Is this normal?

[Ziggster]

I have a C59A with C7RA-A heads. I had purchased NGK B-6L plugs which is the recommended one for my year flathead. These are equivalent to the Autolite 216. The reach is listed as 7/16" (11 mm). Looking at it loosely installed (finger tight), it seems to me to be sitting too low, as it doesn't even protrude into the head. There are two exposed threads left, and if torqued properly, I'm guessing it will go deeper into the head by one thread. Is the plug supposed to sit this low?

[WABOOM]

I wouldn't be doing any "guessng". Torque it and see.

[RalphM]

Looks ok to me.

You don’t want it deep enough for the valve to slap it.

[petehoovie]

Originally Posted by Ziggster

I have a C59A with C7RA-A heads. I had purchased NGK B-6L plugs which is the recommended one for my year flathead. These are equivalent to the Autolite 216. The reach is listed as 7/16" (11 mm). Looking at it loosely installed (finger tight), it seems to me to be sitting too low, as it doesn't even protrude into the head. There are two exposed threads left, and if torqued properly, I'm guessing it will go deeper into the head by one thread. Is the plug supposed to sit this low?

[51 MERC-CT]

This is what an H-10 plug with 7/16" reach looks like installed in an EAB head.
Yours should be OK.

[Ziggster]

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Thanks. The lady pic looks correct. I'll torque it down tonight.

[Ziggster]

I found the original Champion H11 plugs. I torqued both the Champion and NGK to about 21 ft-lbs. and they about the same to me which is good.

[AnthonyG]

They both look good. A good practice is to check valve 2 plug clearance in a situation ur unsure of.

[scicala]

In my mind, as long as the ground strap on the spark plug doesn't go lower than the ledge in the head that surrounds it, there should not be an issue.


Sal