thanks for the reply. i am redoing an 85 f150 with low org. ks. it is a new hobby for me and i am really enjoying it.trying to do all work myself. i am working on a progress gallery on this site as im just starting. the truck came with a 300 six and im switching to a 351ho i found out of a 86 250 with 114ks orig. it is a clean looking engine but am trusting th yard where i got it it is tight.i am installing a blue racer cam 204/214 448/472. also would like roller rockers, pro.product typhoon intake and i have a set of shorty headers i picked up for 100 bucks. i thought the heads would be a good upgrade as i have e5s . i will eventually tear this down and redo but it has low k so iam going to run it for awhile. if you have any sug. my eyes are always open
The older 351 heads 69-74 have smaller combustion chambers(for more compression) and bigger valves than the newer style 351 heads.They would be great as a bolt on head but if you have to rebuild the heads anyway (which is likely with 35 year old heads) you might be better sticking with the heads you have.You can have the larger 1.84/1.54 valves installed in place of your smaller 1.78/1.45 sized valves .I'm not sure on the combustion chamber size of your E5 heads but the old 351 heads are spec'd at 60.4 ccs.You might want to talk to a machine shop and find out which is the best way to go.I've seen lots of these heads at the Barrie Automotive Flea market for $200-300 bucks but they would still need rebuilding.