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Mike Taylor 3601 · 12-02-2013, 02:38 PM

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

12-02-2013, 02:38 PM	#14
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,372 Likes: 355 Liked 308 Times in 103 Posts	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