Head bolts

[RivNut]

I'm getting ready to reassemble the engine from my 64.  While cleaning parts, I noticed that I have some head bolts with a different style head on them. Is this just cosmetic or are they intended for different uses.  If it's only cosmetic, I have a big bin full of bolts from other engines that I can use so the OCD in me will be happy. The one pictured on the left has what appears to be an L in a circle; the one on the right has six lines radiating from the  center. Any comments will be appreciated.

[arnulfo de l.a.]

Ed i cant comment on the specific uses for those bolts but  i have read on various car forums that it is best to install new head bolt when reassembling a rebuilt/ overhauled motor. If i recall correctly the reasoning is that they are weaken due to initial stretching during the initial torque process as well as the many heat cycles they have endured through out the years 

[RivNut]

Interesting. But, I know from reading previous threads that neither the 1/4” longer bolt used for the a/c compressor bracket and the bolts with the stud on the head are not available.  

[BulldogDriver]

As I understand, head bolts for Nailheads are reusable as long as they are in good condition and not stretched (over torqued). They are not TTY (torque to yield) as used in modern motors. Supplies of these bolts are getting slim, I just bought a set so I had spares for my backup motor.

 

Ray

 

[Hazdaz]

 

The one on the right is a grade 8 bolt.    Never go down in grade when replacing bolts.

 

I have never seen a bolt head like the other one, but I highly doubt it is cosmetic.  It isn't a symbol used in industry any more, I don't think. 

[RivNut]

I went out and looked at them again. The one with the weird head is the one that is 1/4” longer. But of the 8 shorter ones, 5 have the same stamping but they are all the same length. Is the 1/4” longer one with the weird stamping just a coincidence?

[SpecialEducation]

Torque to yield bolts weren't a thing until the 1980s. 

Differences in marking outside of the standard grade markings is just a way of differentiating between different bolt suppliers.  When I rebuilt the 1970 Olds 350 that was in my grandmother's F-85, some of the bolt heads had severe pitting.  I had a parts motor that I picked up locally and used some head bolts off it.  Because of differences in markings from different suppliers, I segregated them so all of the visible bolts were matching, and the ones under the valve covers... not so much.  lol

 

[Seafoam65]

In my opinion the different length head bolts on the engine had different markings on them

when the engine was assembled at the factory. Also, head bolts like those can be used over

without any problems with stretching or breakage.

[RivNut]

I found another box of head bolts and coincidentally or not, the 1/4” longer bolts in that box also have the circle on the head. But, the shorter ones with that marking are the same length as the 6 rays radiating from the center.