(Minor question): Water pump bolts have a plastic insert?

[69ISFINALLYMINE]

As I have said before, I am new to MOPARS and just became the proud owner of a 69 Charger.  I am making it road-worthy since it has been sitting for quite some time.  I have a question related to some strange looking bolts.  I replaced the water pump today (383 engine) and noticed that the 4 water pump bolts have some sort of plastic insert in the threads.  It looks like all four bolts were drilled into the threads on one side and plastic was molded in, then threaded with the bolt.  What am I seeing?  These look to be original factory bolts.  Hmmmmmm.

Aside from the miles and miles of threads on the front disc brake caliper bolts, this is the second unusual thing that I have found with this car.
Thanks.
Doc

[RD]

you got pictures? and no...someone did this after.. OEM does not have plastic inserts in threads.  sure it isnt some type of liquid pipe dope that has dried?

[69ISFINALLYMINE]

Absolutely sure.  I ran all foud bolts on the wire wheel to clean them before reinstallation and saw it on all four bolts exactly the same.  No pic and I wish I did but I just finished putting everything back in front of the water pump (pully, fan, belts, radiator).  The only way that I can describe is is that each bolt looks like it was laid on its side and a 1/8th inch hole was drilled into the threads about 3/8 inch in from the end of the bolt, but not all the way through. Then the hole was filled with plastic and the bolt was rethreaded.  I see no reason for this at all, unless it is some sort of a way to lock the bolt in place?  Whatever it is it is tough stuff.  I thought it was thread sealant or loctite and really hit it hard on the wire wheel and it did not come off. Man I wish I would have taken a pic now. 

The bolts look factory on the heads and the work is just way to clean to have been done by someone messing around.  SOMEONE must have seen this before?

Doc

you got pictures? and no...someone did this after.. OEM does not have plastic inserts in threads.  sure it isnt some type of liquid pipe dope that has dried?

[Charger-Bodie]

sounds like someone used automatic transmission tail housing bolts on the water pump.

[69ISFINALLYMINE]

Can you explain?  If the bolts are on from an AT tail housing, what is that plastic crap all about?

sounds like someone used automatic transmission tail housing bolts on the water pump.

[Dans 68]

Sounds like a nylon locking insert...should not allow the bolt to back-out after you properly torque it. 

Dan

[oldschool]

the bolts that hold the fuel pump have the nylon inserts also.they are the only ones i know of that the factory used

[gtx6970]

thermosat housing bolts used this thread locking / sealent method as well

[John_Kunkel]

Since some WP pulleys only clear the WP bolts by a few whiskers there is no room for a lock washer and a self-locking bolt would be a natural for that location. I wouldn't be surprised if the plastic lock bolts are original.