[ponyakr]

there are lots of other heads you can use 2 build a lower comp 455. the 4x & 5c are just 2 that come 2 mind. any of the heads that came on 350's & 400's will raise the comp of a '71-'76 455 with original heads. but be aware that some heads along in the '72-'73 period either did not have all the exhaust bolt holes drilled or didn't even have a boss cast in the heads where a bolt hole should be. again, if you want these head #'s just ask on just about any forum on this site--there are lots of guys here who know all the #'s. i would just avoid these heads totally. now--here's another area where my opinion will differ from most. starting in '71 455 heads had huge chambers 2 reduce the comp down into the 8 range. these heads are useless on a 350 or 400 & are considered junk by most. now i'm not talkin here about '71-'72 455 HO heads or '73-'74 455 SD heads, but only '71-'76 455 d-port heads. the 6H is an example--probably around 124cc chambers. these don't make much comp, but you still have that long 4.21 stroke for low end tire melting torque/starting line jump. of course, the big advantages are that you can use pump gas with no additives & it should be very easy on head gaskets. naturally, it will produce less power & higher ets--but with the rite combo of parts--still no slouch. 1 more advantage i just thought of--initial purchase price of cores should be extremely low. if you can find a pontiac guy whose been using 455 blocks for very long--he probably has a stack of these big chamber heads(if he hasn't sold em for scrap) in the corner of his shop & may give you a set, just 2 get em out of his way. there was probably a time when i had at least a dozen sets--cause every single 455 i bought had a set on it. i never used any because i had plenty of hi comp heads 2 race with. i would consider a low comp 455 a good, low budget gbt motor, which would probably run hi 12's to mid 13's in a lite bracket car like the '68 birds we raced. at our local track, there is no min et required 2 run in the no-e footbrake class--so 2 run 10's & 11's is just spending $ you don't have 2 spend 2 be competitive in the class. but if you just wanna go quicker & have the $ 2 burn--pull out your wallet & make it quicker! just know that you don't have 2 go fast 2 have fun & win races. we won dozens of races running in the 13 sec range against lots of 10 & 11 sec cars. all ya have 2 do is learn enuff about it 2 beat a few chevys!