487 vs. 487x heads

[John Scott]

Interesting...thanks guys.

[Adger Smith]

Jerry,
Figure this one out.
I have a core supplier that hunts castings. The DT racers around here like the 487X head. He said he had several sets of castings that had 993 on the VC side, but in the water passage hole in the deck it had 487X. Could it be the lower part of the mold was for the 487X and they just mated the 993 top of the mold to them? Economy measure by the casting foundry? Use what they had available? I've always thought the X stood for a blueprint change. I wish I had some of thos 993/487X castings just to look at. Humm...

[JRyan]

Adger,

I just looked at one of those 993/487X heads today while arranging my storage. I think they're close to being interchangeable being they're both hard seat heads. GM must have thought so too as they interchanged molds for both as I've seen 993 in the VC area and 487X on the intake runner too. Some of the 993's also have a 493 on the bottom.

Also, I've had a pair of 993's with 152 cc runners. I'll bet the boys with the "Cheatin Bastards" would like those.

Jerry

[Adger Smith]

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.

[Dwight Southerland]

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

[ron mattson]

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.

[Mike Taylor 3601]

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