487 vs. 487x heads

[John Scott]

Is there a difference between 487 and 487x heads? I am looking for 487 but think I may have found a set of 487x. 1971 270 hp 350 is what I am looking for heads for.

Thanks
John

[Don @ Maritime Drag Racing]

Something tells me the 3973487X casting has 10cc more intake runner volume. Not sure where I remember that from and I also seem to recall the X heads were Corvette.

[John Scott]

There seem to be a few different opinions on this that I have found. One theory is that the 487x is the same head but has induction hardened exhaust seats.

[Jeff Kempton]

John; as you've found here and in your post on ClassRacer, most of the info available on 487 vs. 487x heads is based on 40 year old memories and not conclusive data. Generally the only way to find the best allowable factory castings is to gather up multiple sets and pour the runners and then flow each of them, which quickly can become both time consuming and expensive. Expect to have to discard some of them when you find cracks or previous illegal mods in those 40 year old castings too.

It might be a viable option to put your first class legal motor together by using the first set of good, legal castings that you find, while concentrating on building a good shortblock. With a decent chassis and converter that should get you under the Index, and as you gain experience with the combo you can continue to look for the best heads, and then swap them onto your shortblock at that point for an easy upgrade.

For what it's worth, when 461x castings were first thought to be better than regular 461 heads, they were called "Canadian" heads because many of those found had "Made In Canada" cast into them. As far as the hardened seats go I think they were produced mostly for trucks due to the "severe duty" expected of those applications (towing and/or hauling loads puts a lot of heat into the exhaust valves). Just some more hazy recollections from someone trying to remember "facts" from 40 years ago!

Here's the link to the ClassRacer post for those interested:

classracer.com/classforum/showthread.php?t=50653

[ChipperChapman1090]

For what it's worth NHRA lists only the standard 487 on the runner volume list. Max volumes are 161in/65ex