142

185rwhp, that should wheelspin out of corners nicely... goodluck simon!

double the injector size, dump a heap of rum in and 169HP is yours!

Well, i pulled a couple of A12`s down today. One has the lighter crank but has two scuffed pistons. It was out of a 120Y and all of the top rings were broken. The other has a sligtly better bore but the heavier crank. The pistons appear to be in better shape. I might have to make one out of two.

Im also getting a little nervous about big boost after seeing how narrow the ring lands are between the two compression rings!
I might have to keep it to 15psi.

Couple of questions,

What RPM will the stock bottom end handle? 7500? 8000? 8500?

and did all the 120y`s have the lighter crank?

I think 7000.

There ia a formula to calculate piston speed. One book says to keep piston speed under 3500Fpm for cast crank and rods and under 3900Fpm for forged crank and rods.

Piston Speed(FPM)= (Stroke x RPM) / 6

Stroke= 2.756"

The book recomendation brings it to about 7,600rpm for cast crank and rods or about 8500 with forged crank and rods.

It does seem high!

Simon, I believe youll need a good headgasket investment.
A cometic headgasket will allow a reliable setup at 15psi for the
track but a stocky will see disappointment after maybe a few laps.
I know I said 135hp atw will be possible but Im sure your main interest
is a fat torque curve, as this setup wont be as reliably high revving as your
bike head beast with forgies.
If you are using dble valve spring then 7500rpm would be a safe limit.

Thanks Levey and D,
I might have to go to a smaller turbo to get it to come on earlier otherwise i1l end up with a very narrow usable torque band. The turbo i already have wont do much until about 5,000rpm. If 8,000rpm was just ok i would stay with the turbo i have.

Mmmmmmmmm?

I reckon 167Rwhp!

T2 off a ET/EXA pulsar does Boost relitivley early in the rev range, but it does run out of puff in the upper rev range. I settled for a T25, they're cheap and plentiful and very easy to come by. The main reason i settled for the T25 it seems to be a good 'all round' turbo, not too much lag boost comes at around 3500rpm. i wouldn't mind trying a T28, to see if there is much difference?

144.4 HP
Good Luck Simon!