cwilgo63

i have a pair of heads for a 350 andi was wondering if they are special because they have the 13/16 spark plugs. All other 350 heads i have seen lately have the 5/8 plugs. the heads have to be reworked and i was wondering if they are worth the trouble.



thanks

angel71rs

All heads made before 69 had the large plugs. Corvette may have had big plugs after 68, not a vette guy so don't know for sure. They could be run of the mill heads, or from a performance application. One thing to be aware of is that Chevy did not start using hardened valve seats until 71, so there may be more valve seat wear. Check the casting number here for original application:


http://www.mortec.com/castnum.htm

cwilgo63

Thanks,gottanother question... did the headsmade in the 67-69 range come stock with a 60 or 64cc only or did they also have the 76cc...i have heard that the 76cc came later for smog reasons...thanks again

colin911

i just picked up a '69 350, and it has 76cc heads

cwilgo63

thats sux... i was wanting 64cc heads because with the 76cc that i had before all I had was 8.5 to 1. well maybe i can find something that will tell me for sure the size

angel71rs

Some 69 350 heads had big chambers, some had 64cc's. Only way to know what your's have is to look up the casting # on mortec or post it here.

Greed4Speed

Personally, I wouldn't mess with stock heads unless you're trying to keep that engine all original. There are too many alternatives that flow better than stock for a reasonable price.

Black99Cobra

post the casting #'s and i'll ID it for ya..
i'v got the book sitting right next to me
~J