I am having an overheating problem, Wondering what It could mean.
Sorry for the long post.

heres the story
I bought a 350 block to rebuild the bottom end to fix a knock in it, so after the bottom end rebuild, and replacing one of the lifters, I swapped the engine in, starts up, idle's great, no knocking what-so ever. Then My dad goes to get the car hes driving it back, and It overheats so bad that he has to get It tow'ed didn't blow a hose or anything. I am Trying to find more info out about how and when It overheats and under what conditions but heres some of the situation, the heads did not come off during the rebuild, the radiator is new, new waterpump and a working thermastat, the fan Is on all the time as long as the car is on, and when my father drove it he drove it with no air filter.

the reason for no air filter is, after the swap for some reason my father couldn't get the hood on and airfilter unit at same time so he choose to keep hood without filter.

I am hoping that I don't have to replace the heads/ or their gaskets but am able to.

now there did not seem to be build up of pressure in the system from what I understood so I do not think that there is a leak in a gasket or head, the fluid level stays the same.

My only thought as to why its overheating, besides heads/head gaskets, is that he was running it without an air filter so that the only air it could pull from was the hot air the engine was heating up or that the thermastat was incorrect temperature(it works though).


Since I am unable to get to my car my Father is doing the troubleshooting process.

I asked him to try purchasing the lowest temperature thermastat and put the air filter unit and run the car without the hood on.

If its neither of those would it end up being a cracked head or head gasket?

 

Did you say that the system DOESN'T build up pressure? I'm a little confused about that. Your system SHOULD build up pressure, and the upper rad hose should get hot. Check the basics before you go any further. Running it with no filter is not the overheating prob.... but something could easily get sucked down into your brand new bottom end.

 

It doesn't go over 16 lbs of pressure, I mean I don't think that its continously building up.

 

Check the bottom hose. If you can sqeeze it flat, the pump will too when the thermostat opens, thus cutting off the flow of coolant from the radiator to the engine.