Re: 487 vs. 487x heads
 

Jerry,
Wouldn't it be bad to get tossed with a 993 head and they see that 487X on it when doing the CC's... Humm
I'm going to have to run that one by Wesley.

Re: 487 vs. 487x heads
 

Not unknown on SBC heads. I have seen 291s with 462 cast on the bottom water passage hole.

Re: 487 vs. 487x heads
 

487/487x and 993 are all based on the same
Casting group, that is why some have dual
Numbers top and bottom. As far as flow I have
Seen more of a difference between individual
Castings than between casting numbers, have
Seen good and bad 487 or 993 just depends
On the casting more than the number.

Re: 487 vs. 487x heads
 

Someone mentioned 487 487X having hard seat/non hardened seat and spring seat differences, I think if you look the non hardened seat version may have take the older style plugs 3/8 reach w/washer verses the later using .460 reach tapered seat plug, I recall hunting for those casting years ago and seems like there was some that use 3/8 reach and some used .460 reach.

I've seen alot of heads w/ 2 casting #'s all through out years.
I have question have a 291 casting that has date that is a mystery to me
It has a 5 for last digit of date code which would be 65 or 75 which neither match should'nt be 65 has accessory bolt holes in the ends which everything I know about did'nt happen till 1969 and don't know of anything having 291 casting in 75. Could it been made in 1975 and sold over GM parts counter?
Mike Taylor 3601