Head Casting # Question

[tk4td40]

I recently came across a 72' Corvette Engine (350 CI. Block Casting # 3970010) and the Head Casting # 3973487X. My Question is Does Anyone know what the "X" stands for. Any Help would be of great help.

Thank you for your Time,

TK

 

[74Vette]

Is the second number in the head casting an 8 or a 9. I can not find a 3873847 but there is a 3973847 listed. If it is the "9" head then it is identical to the non X head, just used in the late models.


Garson

 

[Jack]

Is the second number in the head casting an 8 or a 9. I can not find a 3873847 but there is a 3973847 listed. If it is the "9" head then it is identical to the non X head, just used in the late models.Garson

When I pulled my 71 base L48 apart it was clear it was an original motor. The heads were both 3973487 ... not 3973487X. My 3973487 heads' valves are 1.94" intakes & 1.50" exhausts. In summary, my 71 base L48 came with small valve 3973487 heads ... not 3973487X. I dunno what if any difference there is between 3973487 & 3973487X castings.

Check the date codes cast into heads & block ... see if the heads' codes coincide with block's date code ... may help to determine if heads-to-block match is likely. My heads are dated March 9 & 10 of 71 and the block date is March 17 of 71 and the motor's pad stamp indicates March 23 of 71 while the car's build date is May 7 of 71. The order of succession seems correct. I'm not certain, but seems that beginning model year 1972 the motor pad stamp was supposed to match VIN ... y'all correct me if that ain't right.
JACK:gap