anyone know anything on a # 3973487X head, all i can find is that it was a 68-73 350 lt-1 head, but the X is supoose to mean 10cc port port volume, suppose to be 330-350 hp head, was cast on Oct 19th of 1971,i also have the 1.94/1.5 valves, one site claimed that the 487x casting had 2.02/1.6 but thats false. but was a lt-1 vette head.

 

That casting was actually used in about 71 and 72, the last of the years of the LT1, after it got smogged like everything else. I don't know about it being around before then. They were decent heads as far as flow; not the best, but pretty good.

On the other hand, their chambers are so large, it's impossible to get decent compression with them, unless you're running a 400 or larger motor, with flat tops; or you use domed pistons which is a highly inferior way of raising the CR.

They sell easily to people with the old LT1s though, for good bucks; that's what I'd do if I had one (!), go advertise on one of the sites that caters to older Camaros and Vettes, or in Hemmings, or the like.

 

If the heads have the extra steam holes in the deck they are off a 400ci motor. Chamber size could be as big as 80cc. Not bad on a flat top 383 or 406 motor with porting and larger valves etc. If you're building a 350 then starting with a 305 HO head (small chamber) is better.
Great for a blown or turbo 350 project thou.

 

3973487X...71-72...350..........75cc chamber

 

hey I need those heads. my comp. is too high and that's just what I need

 

site: http://www.thedirtforum.com/castings.htm

3973487 68-79 1.94/1.50
& 2.02/1.6 165-330 76 CC Chambers
X casting has 10 more intake
cc volume.

and another site: http://www.chevytalk.com/tech/engine/SBC_Heads.html

LARGE CHAMBER PRODUCTION "ON CAR" HEADS

"487" – 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350 LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. The 487X had 2.02/1.60" valves.

btw just finished up the d/s head, all nice n shined up and fresh valves, springs, n seals, just the other argh

 

this was from www.mortec.com

and this is from www.nastyz28.com

1968-72 3973487 350 1.94 1.5
1968-73 3973487 350 2.02 1.6