Casting numbers on HiPO heads?

[6S1568]

Can anyone tell me the meaning of the numbers 19, 20, and 21 that are found cast into the corners of the HiPO heads. I've seen combinations of these on some engines while others seem to have identical numbers on each head. Thanks.

http://www.saacforum.com/gallery/156-100618205921.jpeg

[J_Speegle]

Don't know if that has been discovered yet. May be an identification of the mold (mold number) and nothing more.

[GT350Lad]

Yeah I just look at it and wish I was 21 again!
Ah the fun years 

[Bigfoot]

As an after the fact detail ,.....it let's us know 50 years later when looking at an engine in a car if the heads are HIPO.
And which aren't.

And I'm sure most people here know that but not everyone.

[gt350hr]

  Jeff is right it's the mold ID number the foundry used , nothing more.

[6S1568]

Thanks Jeff and Randy. So I take it that there's no correct foundry number for left or right head, and there's no correct pairing of the numbers 19, 20, and 21. It was all random as to what ended up on an individual motor. Thanks.

[gt350hr]

  That would be absolutely correct. They don't even have to be the exact same date! "Some" are , others aren't. The largest spread "I" have seen is two weeks on an unmolested original engine . Cylinder head sub assemblies were machined and pre assembled in a different area of the engine foundry and sent to a holding area . There is a great video on you tube that shows how engines were assembled. It isn't 289 specific but you get an idea of how things were done and how fast the pace was. These engines were not assembled "with loving care" over several cups of coffee . There wasn't any time to set back and marvel what you just built like we do now.
   Randy

[Bigfoot]

Making me think about Kiwi building his 289.....

[6S1568]

Randy, thanks for the follow-up information, I appreciate it! Denny

[gt350hr]

Making me think about Kiwi building his 289.....

   Yes like the look on his face when we took the heads off and found the engine was .060 over! He thought it was standard because it never ran hot and "everybody" knows .060 ever engines run hot. It was the first engine he rebuilt on his own.