If its bored to much, the cylinder walls become to thin to disapate heat effectively and there you go...overheating. As far as head gaskets, if you install them backwards you wont have any water flowing to the heads and thats where most of the heat in most engines is generated.

Did the guy before you build the engine? Or is it a stock long block?

 

It has an aftermarket gauge. The car also does not like to start when it gets hot. There is no loss of coolant, nor is there any flowing into the overflow bottle. I do not know who built the engine or to what exact specs.

 

does the level match up to the Cold and Hot markings on the front of it?

obviously when its hot it should be at the hot level and vise versa for cold

 

The gauge works, it is not the problem.

 

Is your water pump flowing properly? Take the cap off the radiator while is it running (cold) and look to see if the coolant is flowing. Where is the gauge attached to the motor at? Intake? Check to see if it is in coolant.

 

just geta a comp gauge and check compression in each cylinder it will tell u if u have a blown headgasket or rings are worn, if u have say 140 pounds in all but 1 cylinder and u have 115 in thats one,,, then its a blown gasket if they are two cylinders side by side...or even in a just a stand alone cylinder... doesnt take 20 min to do it.. take out all plugs b4 u do it tho//

 

With a blown HG, wouldn't I lose coolant?

 

not always, there might be air trapped in the cooling system.
run the car at idle for a while without the rad cap on.
if the coolant level drops there was air in there, just make sure you top it up.

 

how do you know it overheating?

if your not loosing any coolant? if you seeing steam but not loosing coolant its probaly your cap.

 

that could be a sign of the TFI going bad.
it could be something as simple as the radiator cap needing replaced, if its losing pressure your car will over heat