Spark plug

[ericcarr]

Ok, I finally got the new yo me motor installed in my 2990 sea ray sundancer. The donor motor was supposedly out of a mi 80’s amberjack, 7.4. I noticed that the spark plugs that was in the amberjack was a ngk br…, can’t remember the actual numbers. But I grabbed my spark plugs that I took out of my 1990 7.4 & noticed that when I tried to insert my plugs into the heads they pretty much wouldn't go all the way in as the hex part of the plug was rubbing on the sides of the spark plug hole. Also, my plugs from my 1990 7.4 was about 3/8” longer than the ones from the amberjack, the threads anyway.

 

[dubs283]

Could be different heads on your donor motor. Is there a difference between valve covers? One stamped and rounded corners vs cast and sharp edges?

 

[ericcarr]

Could be different heads on your donor motor. Is there a difference between valve covers? One stamped and rounded corners vs cast and sharp edges?

Well, my valve covers went from my 1990 to my donor motor so I’m guessing it’s still a generation 4 motor.

 

[ericcarr]

 

[ericcarr]

Also the plugs with the red paint on them came with the motor, the AC Delco’s were in the motor that I originally had in this. As you could see there is quite the difference in length along with the thickness of the hex head

 

[Bt Doctur]

in the first pic the plug on the right is not what you find in marine engines. MR43T is the short reach, MR43LTS is the long reach

https://www.napaonline.com/en/p/AC_R43XL

https://www.napaonline.com/en/p/AC_R43XLS?impressionRank=1

Still should be 5/8 ths socket

 

[Bondo]

Ayuh,..... The plug on the right in that picture, is the wrong plug for a BBC,....

Edit,.... What BD says,....

 

[SternDriveEd]

Look closely at the seat of the spark plug. The one with red paint is called a tapered seat. The cylinder head is specially machined to match up with this style spark plug. The other spark plug uses a flat gasket to seal against the cylinder head. Again the cylinder head on some engines is specially machined for it. They are NEVER interchangeable with each other. Also, I hope you didn’t damage anything when you screwed in the long reach spark plug.