What Does This Stamping On The Head Mean?

So where do I find these part numbers?

 

In the parts manual! Sorry for the short answer!
Oldtime's reply #40 pretty much sums it up. There was likely one head casting (with a specific number), but depending on how it was machined, it could become several different part numbers, in this case, different compression ratios. The hand stampings likely denote the final product, its just we haven't yet figured out the cross-reference. It would have made sense if the stamped 3 digits correleted to the last digits of the part numbers, but that would be too easy!
-Donny

 

So with a '58 that spent its entire life on a ranch in central Texas and nothing stamped on that back machined area, I'm gonna assume it's the standard 6.9 and move down the road.

 

Anyone want to chime in on this point?

 

According to the parts manuals the different heads were painted specific colors.

# 800572 Head, cylinder assembly (Ratio 6.9 to 1) Color blue for use under 5000' altitude
# 649172 Head, cylinder assembly (Ratio 7.4 to 1) Color black for use over 5000' altitude
# 800569 Head, cylinder assembly (Ratio 7.8 to 1) Color yellow for use over 10,000' altitude
# 911689 Head, cylinder assembly (Ratio 6.48 to 1) (Export only)

I have only noticed the special colors on replacement heads and not on factory built engines.

For example CJ's were standard having 6.9/1 CR heads but the factory painted heads normally seen are virtually always black and were not blue as the Universal Parts List suggests.

6.48 / 1 was the early Std CR.
The 6.9 CR became standard for a couple reasons.
1) Relatively low CR allows an engine to be hand cranked if desired.

2) These engine were designed to operate on uncracked gasoline (about 69 octane).
6.9 CR at most any elevation should not cause pre-ignition if running uncracked gasoline.
Higher engine CR can produce pre-ignition concerns unless the fuel octane is increased above 69.

The factory Dynomometer chart represents standard engine components.
The Std. CR of 6.9 cannot fully utilize the octane we have in todays cracked gasoline.
Today we have cracked 87 octane gasoline or higher.
So we can easily increase from the standard CR without pre ignition concerns.
I believe that increasing the CR certainly does increase the HP.
The HP increase will exist albeit a near undetectabe increase to the operator.

 

Very interesting to hear about the "color codes". I think every stock unmolested engine I have ever seen was black. Many "rebuilt" F134s seemed to have ended up Chevy orange!
-Donny

 

Blastomy!

 

My 64 does not have any stamping.