You need to measure the cylinders and combustion chambers and calculate
the compression ratio. If you are using stock or flat top pistons and
haven't radically shaved the deck or head, you ought to be able to
operate on premium unleaded or perhaps even mid grade.
Mid grade works fine in Huxley. He has flat top pistons and is at
something on the order of 9.5:1 ratio.
In your case, you may want to try premium and if you get no pinging,
back down to mid grade. You want to use as low of octane fuel as will
run without detonation.
Mark Campbell wrote:
> I'm very close to finally getting my 72 Spitfire on the road (inspection and
> front-end alignment this Saturday).
> Now, what grade of gas would you recommend running in a 1500cc (sorta)
> 1492cc (+0.020)
> Kent Fast road cam
> Crane ignition
> Dual DCOEs
> Ported/polished head
> "Pacesetter" headers
> High-energy coil
> and soon, Monza exhaust (I know it's loud, but I already have it, and stock
> has had it.)
> You know, the standard stuff... :)
> Mark Campbell
> 1972 Triumph Spitfire Mk IV (...years in the making...)