iv got a pair of 6-x heads. 1 is a 6-x(8) and 1 is a 6-x(4). i want to put these on my 455. should i get machine work done on these so they both have matching cc's? i was thinking around 80cc?

 

6x heads are great for a 455, one was a 350 head, and one was a 400 head, so they are different, i cant remember if the 4 or the 8 was a 350. i would get a matched set and deffinitly get them checked for trueness before i put them on. also make sure your intake is correct for your heads. the exhaust cross overs on some heads are open and some are not. again i cant remember which is what, but your machine shop will know. if you dont do that you will have a leak at the center of your intake. wallace racing should help, they are pretty knowlegeable on heads, a 4x with a 4 stamp would be better, a 7m5 72 head would be best

 

i have a set of bare heads off a '74 455

prh