Re: Does anyone have some real data from the new head choices out there?

cool40 November 6th 2015, 10:18 pm

rmcomprandy wrote:
cool40 wrote:
rmcomprandy wrote:
HorsinAround wrote:

Is 6500 rpm on a 557 a realistic expectation?

YES ... that is about the upper limit, to be able to spin it higher and continue to get better results with that 4.500" stroke gets EXPENSIVE.
I was hitting the limiter @8000 last time at the track.

With a lightweight rotating assembly, using high compression with thin rings and a block with a stiff bore and a well done inlet, you can get there ... it certainly was not a regular lower cost engine assembly.

yes Randy the key word in your reply was EXPENSIVE, Laughing

rmcomprandy November 7th 2015, 12:14 am

cool40 wrote:
rmcomprandy wrote:
cool40 wrote:
rmcomprandy wrote:
HorsinAround wrote:

Is 6500 rpm on a 557 a realistic expectation?

YES ... that is about the upper limit, to be able to spin it higher and continue to get better results with that 4.500" stroke gets EXPENSIVE.
I was hitting the limiter @8000 last time at the track.

With a lightweight rotating assembly, using high compression with thin rings and a block with a stiff bore and a well done inlet, you can get there ... it certainly was not a regular lower cost engine assembly.
yes Randy the key word in your reply was EXPENSIVE,

AND, even the good 557's which will rev to almost 8,000 RPM are not making any MORE positive horsepower after 6,900 RPM when using a conventional port head; P-51's included.