No heat from heater core when radiator cap goes on

I want my 57 chevy back! Now I have a 84 chevy c10 pickup and have
heating issues. First installed new water pump, flushed out heater
core (nice flow afterwards). Put in two differnt thermostates. Second
one high quality. Let run for 50 minutes to blead air out. Results no
heat unless cap is off. Told head gasket could be bad. I dont see
white smoke nor build up of water in oil. Totally lost on this problem
any one with help on this issue, please contact me. I was told maybe I
was sold a water pump with reverse fins that would be used for
sepintine belts. When I accelarate the engine with the cap off, fluid
gusses out of the radiator.
Thanks for your assistance.

On 15 Jan 2007 16:06:14 -0800, "57kid" <hotrod_1957 RemoveThis @msn.com> wrote:

>. When I accelarate the engine with the cap off, fluid
>gusses out of the radiator.
>Thanks for your assistance.

Uh, no... That's a good indicator that something is really wrong!

The cooling system works by sucking water from the bottom of the
radiator, circulating it through the engine and letting it flow back
into the top of the radiator. If you are getting a gush of water at
teh top, something is terribly wrong!

A blown head gasket won't always contaminate the oil. Check for
combustion gases in the cooling system, do a pressure leak down test,
and check to make sure you do have the correct pump on the engine.