can anyone tell me the valve size of this cast number 3973487. and if its a good head or not if not then i might just order the new summit heads #SUM-152123. the only thing i can find on them is they are 71-71 350 LT1 and they have 75cc chamber.

 

Any (factory) chevy head with a 75cc chamber is one that you shouldn't buy, unless you want a head that lessens the performance of your car.
Actually, on second thought, there are some valid reasons to buy a set of those. Say for example, you're broke down somewhere and about to be sacrificed by satan worshippers if you don't get out of town, and that's the only head you can find.
They can be an okay head for a 350 truck motor too.
Keep shopping...
Tell us what your application is, maybe someone can make a suggestion.

 

its just a 350 hyd cam. dont know what cam to run yet.
cant decide if i want to go back to carb (will have to buy the carb and intake) if i do i will go vortec with the XE274 or XE268

i have the TPI setup with 165ecm everthing and i have polished it and just need some heads but might go with the summit ones i posted above and just work the 2 center holes to fit the heads.

so iam stuck performance with the carb setup? or show and MPG with of the TPI?

and iam wanting to get into the tunning with the FI. the car has been parked for 4 years and i just want it running again

 

What heads are on the engine right now?

 

none really iam about to send the block to the machine shop and the only heads i have are the 487's but i wont be running them if they are that bad. how much do the L98 heads go for ???

 

If you already have some 487s and you're down on $$ then you could run them. I just wouldn't suggest investing in a new set, or sinking much money into the set that you have.
If you have the block bored and zero decked then you'll end up with 9:1 CR +or- with the 487s, which can be okay if you're using a small cam.