OK here is my problem. I installed a Jegs lightweight plastic radiator on my drag car. This radiator has a plastic cap with no venting and the radiator will push water out the top after i cut the engine off. The radiator is a little below where the hose connects to the thermostat housing. If I order a new aluminum radiator with a vented cap will it work or do i need to have the radiator vented above the engine. I am getting frustrated and tired of spending money on new parts. thanks for any help

I would treat it like an ordinary rad without an expansion tank. Leave 1/2 to 1" of airspace below the filler neck to allow for coolant expansion. Or have you done that already?

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I lowered the water level and everything works fine as long as i have the electric water pump working and the engine running. As soon as i cut the engine off and the water pump off it wants to push water out the top of the radiator.

That's due to heat soak. The engine is still hot but the water pump is no longer circulating and there is no air going across the rad, so the water temperature rises, causing it to expand. But it sounds like you knew that already... How much air space did you leave below your filler neck?

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.