balancing not only the crank shaft but also the conrods and pistons.
A full bottom end balance will get you to run higher than 8500rpm , perhaps as much as 9500rpm with quality bearings and valve train components.
I paid $1150 for my race ported head but it was a new old stock item never used before so I was wraped with the price I got it for

I just had a problem with mine, I ajusted the ignition timing from 10 degrees to 14 degrees and left the plugs in, the revs straight away went from 4000rpm tops to 5800rpm just by changing the ignition timing alone.
I definately think it is spark related and would be looking at borrowing a timing light to check ignition timing mate

running a cheapish tacho, $130 with a shift light, I will disconnect it and see how it revs, well I will guess how it revs by the sound of the engine

or fwd offset wheels

just set timing to 14degrees, a noticeable increase in revs from 4000rpm up to 5800rpm getting there slowly!

brand new electic pump 3 psi.
definately not fuel issue

Craig had this engine in his coupe race car and the only exhaust on that was a 2 1/2" pipe sticking out behind the passengers door not much of a full system though?
It has to be the plugs surely?
Mines playing up again I have had enough of dattos this month

yep that will also help build power you basically want the engine to flow nice and easy so a good cam with a fair amount of duration with a pair of sidedraughts or even a weber 32/36 will probably get you near that mark

by porting the head it won't make any extra power but will allow for more power to be made with bolt on's and a camshaft, basically if you had all the performance goodies bolted to your engine it will still only make as much power as the head can flow, so by porting the head you will now be able to build power from there on

IT'S BAAAAAAAACK!
That damn problem is back again actually it is always there unless I change plugs all the time.
I have fitted an electric fuel pump, new cap and rotor to the datrats bluebird series 2 dizzy, new NGKBP6ES-11, at which point it ran perfectly but this week it's crap, major crap wont rev past 4000rpm, checking wiring to the coil, distributor for any cracks or shorts and no noticable faults.
Any body have any suggestions before I switch back to stock dizzy and coil and throw this (suspected) piece of crap in the bin?