Help with radiator cap spray

[Lee Mitch]

I have had a reoccurring problem of spray coming under the radiator cap and decorating my hood. It occurs on longer pulls (up a hill) regardless of environmental ambient temperature. It does not occur with increased rpm. I have a moto-meter that works (tested it), and it indicates that my engine is not overheating.

The timing is dead on. I increase fuel and slightly retard spark when pulling a hill.

What gives? Where would you start? What would be other symptoms of a head gasket problem? Anyone think that could be it?

Thanks!