just rebuilt my 68 289 .Started right up after a cuople minutes running coolant started pouring out the radiator.motor was not hot at all.let it run until thermostat opened up.filled radiator back up.Let motor cool down and restarted the motor.same thing happened started shooting out the over flow.also have a small leakon the back side of the motor.has this ever happened to anybody

 

If they are over filled then that will happen. If it ran for a few minutes and then started coming out, then that may be normal if you didn't have the cap on.

 

That is pretty normal. Pressure will build up in the cooling system when the engine is idling. That is why if you are going to run the car with the radiator cap you need to give the engine some throttle to keep the pressure down. That is also why your car will spit coolant when you idle but will be fine at speed.

 

thanks for the info.but the one time i had the radiator cap on and it shot out the over flow tube.what is the correct amount of coolant i had it just above the cores in the radiator when this happened.also do you think the little drip in the back will seal itself or maybe a little stop leak or change the head gasket.

 

Blown or improperly installed head gasket will cause the radiator to overflow. If you already have a leak in the back of the head then I would look at tare down...

 

Something does not sound right. I would NOT put stop leak in. Fix the issue. Stop leak is for people who are need their car to run another 1000 miles before they ditch it. Like LCC said, it sounds like you may have a head gasket issue. Are you seeing white smoke out of the exhaust? When you run the car with no cap, when the thermostat finally opens, do you see bubbles? Do you have coolant in your oil? Do you have oil in your coolant? I would get the "little leak" fixed and then troubleshoot your spitting issue. FYI, the proper amount of coolant is slightly lower than the cap but covering the cores when cold. This gives some room for expansion when the pressure comes up, without spitting all the time.

 

there is no oil in the coolant and no coolant in the oil.no white smoke out the back.im just going to go after the head gasket.and start there.is there a wrong way to put the head gasket on.or are they pretty much universal.thanks for all the help.also which way is the flow of the coolant.does it go through the water pump to the motor back through the upper hose or down through the upper hose first