overheating problem with 350 small block can someone help please??

Dear Reader, I own a 1978 Oldsmobile Cutlass Supreme 2dr RWD. When i bought it the stock engine was already swapped. I did a tune up on it (just plugs
wires and coil) and in the midst of trying to get the right parts for the tune up i was able to identify the motor that is in there as a Chevy 350 small block from like a 1990-1993 chevy pickup (it has fuel injectives). I also replaced the radiator with a brand new radiator. I had been driving the car back and forth to work every other day approximately 30-35 miles one way. The engine sounded fine and ran fine, matter of fact i was outrunning most of the new stuff on the freeway. One day i overheated about 5 mins from home so i pulled over let it cool off and took it home. Since then i replace the thermostat and went about driving it for about 4 more days until it ran hot again. i was running with out a overflow tank so the hose that i had blocking off the overflow passage had burst and i lost all my coolant out the passage where the overflow tank was suppposed to go. i bought an overflow tank, replaced the radiator cap, and refilled the radiator again, and replaced with yet another thermostat. it ran hot again, but it takes it like a good 5 or ten miles of strenuous driving b4 it runs hot but when it does run hot all the coolant bubles into the overflow tank then out the overflow tank along with steam. I totally removed the thermostat while it was hot one day and held it up to cool air with tounges and watched it close so i knew it wasnt the thermostat. i ran it without the thermostat at all for 5 to 10 miles and it overheated again. i checked the oil, there is no sludge or signes of moisture, the coolant looks fine but i loose almost all of it out the overflow tank everytime i run hot, and there is no water coming from my dual pipes. This is soooo frustrating because i have put so much time and money into the interior because i thought the motor was straight. I love this car, what could it be, how do i fix this???? im no novice mechanic but i will get under that hood and go to work, somebody help please. Please tell me its not a head gasket!!!!!!!! whoever put that engine in did such a good job converting it and getting her running right, can you help, keep in mind she still runs strong as a bull, she just overheats too quick.
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Cutlass87 wrote:

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airflow. Is the rad blocked? Look between the A/C condensor and the rad to make sure you don't have a plastic bag jammed in there or something.
fan - clutch fan? Is it working properly? Do you have a shroud?
What does the temp gauge do? read normal and then spike? keep climbing?
Are you sure the rad is big enough? you might need a 3 or 4 core rad in there if you're making a lot of power and throwing off a lot of heat compared to the stock 305 that was in there.
last, but not least... timing and carb jetting - if your timing is way agressive, you can start running hot.
I suspect it's probably your new rad just is too small for the amount of heat you're making.
Ray
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ray wrote:

Thanks for your reply Ray! yes its a clutch fan, and it is working fine and spins strong, i put a fan shroud on and i havent notice anything blocking the radiator, is there anything else that i can do to ensure that i don't have head gasket problems because i don't think it is, yet i cant get the engine to run at the correct temperature. Unfortunately i don't have a guage ( i probably need to put one on there) I just have a light that will come on if the car has been ran too hot
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Cutlass87 Wrote:

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I think a compression test can diagnose a blown headgasket. Or a leakdown test.
And/or if you pull the plugs, if one of them looks like it's been steamcleaned then it's a sign of water getting in there.
I'd consider getting a cheap $10 mechanical gauge and see what's going on...
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Cutlass87 wrote:

Seems to me, you're avoiding the obvious, the water pump. I've seen older ones with the impeller almost worn to nothing. Have a peek, but have a new gasket ready when you do. And.... consider running the engine hard with the rad cap off. When hot you should see movement in the top of the radiator when the thermostat opens. . . . my two cents.
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