Super-mini wrote:
Gday GR,
if you dont mind, approx how much $ are we talking for one of these
and why will it be better than the 16v heads available?
(including bmw motorbike head?)
thanks
super-mini,,,, some of the problems with "some" 16v cyl heads ability to flow is the lack of avaliability of decent amount of valve "Lift",,, the buckets that are used ontop of the valves for the cam lobes to run on, are aften not very big in diameter & that small diameter restricts the size (or height) of the egg (cam lobe) able to be used,,, Too big a cam used & it will effectively fall over the edge of the bucket & shred everything in the process,,, in the old Lotus twin cam heads it was quite common to "up-size" those buckets by using the bigger Alfa Romeo ones etc (larger diam & meant machining the holes in the head bigger to suit) & then they are able to run bigger eggs (cam lobes) which, in turn, gives higher valve lift & (in some cases,,, but not all)---> More flow.
When we ae talking the difference between one of the 16v heads only able to run about 10mm of lift,,, & the average A-series head can run past 13mm,,, well it makes a big difference in flow for full race donks.... not so much of a concern for street engines tho.
altho in saying all that,,, there is "usually" & in most cases, a far far greater "valve curtain area" avaliable with the 16v heads than any of the A-series type heads (be it 5, 7, or 8 port) ,,, so there is a fair bit of give & take involved ,,, it comes down to what you want to do with the engine,,, road, rally or full race.... & how much money you`re prepared to fork out.
I don`t believe any std-ish 5, 7 or 8 port A-series head can match a std-ish 16v K1200 Bimmer head or large valve KAD head tho,,, I`m not positive on the KAD valve & bucket sizes but with the K1200 Bimmer head`s 4mm valve stems & 2x 26.5mm inlet valves in each cyl,,, times that by 10mm + valve lift,,, well you can work out the combined valve curtain area easy enough... it doesn`t take a rocket scientist to work out which head wins in the flow dept,,, & of course the quad throttle bodies & most of the efi stuff allready comes with the Bimmer heads
So,,,, Now lets work on improving that std-ish K1200 cyl head the same way anyone worth their salt ports out & fit`s larger valves & opens & de-shrouds & shapes & pollishes chambers,,, lets add those bigger buckets & larger cams togther into the package & lets now get well more than 1/2" (like maybe 15mm) of lift yeah ????,,, then we start a whole new ball game & a far far greater avaliability of flow at higher engine revs,,,, But that`s not to say the low end torque is any better in the bargain.... so again ,& it`s as GR says,,, that`s the sort of thing used for "Full-Race" minis,,, & of course the K1200 heads allready come with 38mm quad throttle bodies
One of the beautys of the age old A-series cyl head is it`s wonderfull low-mid & top end torque creating attributes,,, i believe this will remain similar with the 7 port, so it`s a dam good thing,,, added to the fact that (Like i stated on the other thread about these design heads) is the "Value for money" part of the package where your std issue A-series 3-pipe exhaust & std issue A-series cam will still be retained, so it`s a fairly cheap opperation to change over to a 7 port cyl head (compoared to a 16v conversion) ,,, & that`s all good for the average Joe/Jane Doe race mini driver
& as GR says,,, dam good to fully work one to use as a full race item, obviously there are some good numbers happening
Now,,, in saying all that,,, i havn`t seen a 7 port in the flesh yet, i have no experience with them what-so-ever (Yet), so what i`m talking about comes from pure physics & general cyl head design knowlege & experience,,, obviously GR will sort out where within the rev range these 7 port heads will work best ,with what cam & lift & with what valve sizes to suit the differing engine capacities & applications,,, it`s all about "horses for courses" remember -----> """This goes with that at Susan"""
I`m still on the turbo EFI 16v game & i`m sticking with it for quite some time,,,, but if a 7 port head landed in my lap then maybe i would test it on my 1510cc donk
There is also another problem with the 16v heads for anyone concidering using them for N/A Full race applications is the need for special pistons to be sorted to creat some "Decent" race compression ratio (like 13.5:1 or therabouts) The 5, 7, & 8 port heads can simply be shaved to suit nice std issue flat top , allready tried & proven race pistons,,, A Bimmer headed race engine would need some dome-top pistons made to suit , to make some decent full race compression,,, that`s another reason why i simply turbo charge mine
Roady Bimmer applications are not an issue tho.
Elder & GR are doing good things.
sorry for the long rant,,, i just thought that might save GR some time