Head bolt size...help

[jdtower23]

I am worried that I made a major mistake....what is the correct size for head bolts in a 4.3 OMC? I used a 3/8 tap....is it 7/16? If so, will this hurt anything?

 

[jdtower23]

Re: Head bolt size...help please!

Re: Head bolt size...help please!

Can anyone chime in? the 3/8 is smaller than 7/16th right? So it shouldn't hurt anything? my old head bolts thread in easily now....

Thanks!

 

[Fishermark]

Re: Head bolt size...help please!

Re: Head bolt size...help please!

I don't believe the head bolts are 3/8ths... but if your old bolts still thread in easily, you apparently didn't hurt anything.

 

[jdtower23]

Re: Head bolt size...help

Ok, I think maybe the 3/8 was just slightly smaller, which in a way could be good.....

Thanks

 

[Bondo]

Re: Head bolt size...help

Ayuh,.........

A 3/8"x16 tap will rattle around thru a 7/16"x 14 Hole without doing awhole lot of Anything............

Btw,............The Holes usually run 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", etc.....

 

[jdtower23]

Re: Head bolt size...help

Well, the tap did seem to help.....I also cleaned the holes with a brush....they threaded pretty easily with my fingers....you think i'll be ok? Heads are on now.....

 

[jdtower23]

Re: Head bolt size...help

I'm a moron! I did have the right size.....I remembered seeing 3/8 drill size underneath and got that in my head.....i had a 7/16" x 14 NC bottoming tap....what does the NC mean?

Thanks

 

[Reel Poor]

Re: Head bolt size...help

what does the NC mean?

National Course = course thread bolt
National Fine = fine thread bolt
There are others also.

 

[jdtower23]

Re: Head bolt size...help

OK, pretty sure the head bolts are course thread....so I had the right tap!

Thanks a lot,
John