When I did mine, used rotary grinding stones to smooth
the passages and remove material to ease the flow of
the mixture, also matched the ports to the manifold
which were off by a bit in a couple of cases. Also
removed a little material around the inlet valve stem
to free up the flow. Be careful when working around
the valve seating surface. A couple of slips and I
had to do a valve job to remove the 'oops' marks.
Grinding work best done before the head is machined
and valve job done.
The manifold surface after this was free of ridges,
etc. but not polished. A polished surface is too slick
and does not add to the turbulence which aids the
mixing of the fuel and air. Smooth is okay, polished
is not.
Aloha
Peter O.
--- Ian Stuart <Ian.Stuart@ed.ac.uk> wrote:
>
> On Tue, 2002-11-12 at 10:20, John M. Baker wrote:
> > Ian Stuart mentioned carb/manifold tweaking as one
> option to improved
> > performance, among many. Ian, are you talking
> about polishing and making sure
> > the manifold matches the ports? If you can provide
> more info on what might be
> > done I would appreciate it.
> There are various options here.
> 1) A carb with a better flow-rate (eg an SU)
> 2) Inlet manifolds that have better flow
> charicteristics
> 3) Getting rid an all sharp edges between the carb
> and the inlet valve
> (which would include your comment about the ports
> and manifold holes
> matching in terms of size and position. :)
>
> Note: when one talks of "polishing" the inlet ports,
> I was told that
> "mirror-smooth" is not what is wanted. The ideal is
> a very slightly
> rough surface so that the fuel-air mixture continues
> to swirl'n'mix, yet
> does not eddy behind any sharp edges.
>
> There are numerous books on engine performance, so
> find one that
> concentrates on the head :)
>
> BTW: The inlet manifold that Authmotive makes covers
> #1 & #2, #3 simply
> requires several hours of patient work.
> (I don't have any of their kit, though I do know
> Roland, the head lad
> there :)
>
> --
> --==++
> Ian Stuart: Edinburgh University Data Library.
>
> Information is not knowledge
> Knowledge is not wisdom
> Wisdom is not truth
> Truth is not beauty
> Beauty is not love
> Love is not music
> -- Mary.
>
> Personal web site: http://lucas.ucs.ed.ac.uk/
> _______________________________________________
> LRO mailing list
> LRO@land-rover.team.net
> http://land-rover.team.net/mailman/listinfo/lro
U2 on LAUNCH - Exclusive greatest hits videos
http://launch.yahoo.com/u2
_______________________________________________
LRO mailing list
LRO@land-rover.team.net
http://land-rover.team.net/mailman/listinfo/lro
This archive was generated by hypermail 2b30 : Tue Nov 12 2002 - 12:58:47 EST