to much pressure in radiator??

[whereyat]

i recently installed a new hp 302 in my truck and with it new pulleys and water pump. the new motor has the truck water pump with the smaller car pulley on it. it seems that when i run up the rpms the water is being blown out of the overflow hose. i put a 16 pound cap and still having the same problem. this is a new radiator that worked great with the old motor and pulley. could it be the smaller pulley is pushing the water faster than it can pass through the raidator? or should i be looking at something else? any input is appreciated.
the water doesnt blow out when revved sitting still but when i get on it hard driving.

[td]

how long have you been driving it since you last filled the rad? could it be its just blowing out the exsess fluid there's not room for when the system builds up presure?

[whereyat]

i have to keep adding coolant, it blows out enought to see the core of the radiator, a gallon atleast. i dont think it stops getting pressure when the water is low.

[convincor]

could be spinning the pump to fast causing cavitation which will cause foaming/expansion. I'd try going back to the larger pulley.

[whereyat]

thats my next step. thanks, ed

[QC]

I doubt if the truck pump is any different than the car pump. The pressure is caused by temperature, not the water pump. My experience has been that if you fill the radiator more than about an about a half an inch over the core the extra will be forced out when the engine gets up to operating temp. Without an overflow system you will never be able to keep the radiator completly full.

[td]

I doubt if the truck pump is any different than the car pump. The pressure is caused by temperature, not the water pump. My experience has been that if you fill the radiator more than about an about a half an inch over the core the extra will be forced out when the engine gets up to operating temp. Without an overflow system you will never be able to keep the radiator completly full.

that was the same point i was making but he say it continues to loose coolant even after the excess has been lost, he has to keep adding coolant. i'd say stop adding coolant and see if it stops this will let you know if you have a real problem or if its just loosing the excess in the system. if you need to you can take a container of coolant on the road with you just to be safe.