Unshroud AA 914 Heads?
Posted: Tue Dec 24, 2019 12:13 pm
Hello All,
This is my first post, but I've been stalking this 4rum for awhile. I am in the development stages of a conversion (1960 bug) engine build. I have the cooling (DTM), case (1.7 914), exhaust (A-1 Sidewinder conversion), and a recent set of AA knockoff 2.0 914 bare heads (black Friday AA deal). At this point I am planning a 2258 78x96 with a Webcam 163/86b and all the valve train goodies (maybe even the Type4store cam kit variant).
When using the UEM engine calculator https://uempistons.com/p-27-compression ... lator.html I'd like to keep my compression around 8.8:1 or lower. This would require me to have 65cc chambers with .040 deck. Per Ham https://newsite.hamheads.com/2017/07/01 ... knockoffs/ the chambers in these heads will be around 58cc when built. The jump from 58cc to 65cc seems drastic. I would have European Motor Works or Headflow Masters do the work, but 7cc in each chamber would be a lot in an already large chamber.
Is unshrouding 7cc even possible/advisable in these AA knockoff heads?
Or should I run a smaller crank(76mm), increase the deck (to .045) which would require only 62cc chambers? Unshrouding 4cc seems more doable.
I could also increase CR to 9:1 with 78x76, .045 deck, and 62cc chambers (4cc unshrouded)?
Obviously all of this is in the planning stages as my heads are still bare. I wanted some opinions and options to mull over. 2258 seems to be a common combo. What CR are people running? What CC are your head chambers? What direction should I be looking?
Thank you
- J
This is my first post, but I've been stalking this 4rum for awhile. I am in the development stages of a conversion (1960 bug) engine build. I have the cooling (DTM), case (1.7 914), exhaust (A-1 Sidewinder conversion), and a recent set of AA knockoff 2.0 914 bare heads (black Friday AA deal). At this point I am planning a 2258 78x96 with a Webcam 163/86b and all the valve train goodies (maybe even the Type4store cam kit variant).
When using the UEM engine calculator https://uempistons.com/p-27-compression ... lator.html I'd like to keep my compression around 8.8:1 or lower. This would require me to have 65cc chambers with .040 deck. Per Ham https://newsite.hamheads.com/2017/07/01 ... knockoffs/ the chambers in these heads will be around 58cc when built. The jump from 58cc to 65cc seems drastic. I would have European Motor Works or Headflow Masters do the work, but 7cc in each chamber would be a lot in an already large chamber.
Is unshrouding 7cc even possible/advisable in these AA knockoff heads?
Or should I run a smaller crank(76mm), increase the deck (to .045) which would require only 62cc chambers? Unshrouding 4cc seems more doable.
I could also increase CR to 9:1 with 78x76, .045 deck, and 62cc chambers (4cc unshrouded)?
Obviously all of this is in the planning stages as my heads are still bare. I wanted some opinions and options to mull over. 2258 seems to be a common combo. What CR are people running? What CC are your head chambers? What direction should I be looking?
Thank you
- J