cooling system being weird

[pack]

just had my head rebuilt inc a new cam so i had to get it tuned
had my car on the dyno trying to get tuned.
it was on there for 25mins running cruising below 3500-4000rpm everything fine
as soon as we did a power run at only 10 psi she got hot and coolant started coming out of the resivour and there was lots of air in the system

let it cool down a bit, topped up the coolant and did somemore cruising and its fine

im thinking that there is air getting into the cooling system somewhere under load?
anyone got a better explanation?

[uk525td]

sounds like you never bled it fully when it was rebuilt?

[ShapeShifter]

Or big detonation problems.
Could be running very lean under boost.
What was the AFR?

[pack]

i bled the system numerous times
and the afr's are good the tuner got that sorted

[ShapeShifter]

So than what is the AFR?

Have checked for a stuck thermostat?

What have you checked?

[pack]

between 14.5 to 15 with no load and around 12.5 under load
and a stuck thermostat wouldnt be fine one minute and shit after a run

[ShapeShifter]

So, what have you checked?

Those are not the best AFR's.
Sounds far from sorted.

[janders211]

have you compression tested it? Pulled Plugs? Measured actual ignition timing on the dyno?

[jockine30]

sounds like you never bled it fully when it was rebuilt?

what do you guys mean by bleeding the system?Are you guys talking about draning the old antifreeze and replacing it?

[uk525td]

no just about getting hte air out properly, they can be a bit tricky sometimes