Just replaced my head gaskets, water pump ,timing belt, idlers ,tensioner ,valve ajustment ,new subaru tstat ,subaru coolant . no leaks car overheats when im not moving but only if driven if i keep it at 3000 rpm in front of my house until it heats up nothing happens and heat temp gauge spikes at 75% before tstat opens

Know the history on the coolant? If tap/spring water's been used, mineral deposits could be clogging the radiator. Long story made short, I had a '97 OBW with the  same issue. Finally took the radiator out, flipped it over, shook it, and got deposits the size of my thumb out of it.

 

If you've got access to one of those fancy infrared thermometers, I believe you should be able to scan over the radiator and see if a section's clogged or not. Whatever section is clogged should be colder than the rest.

Kaizoku,

 

For such an instant and dramatic change to occur after a head gasket change, suggests to me that the head gasket orientation is incorrect. Some head gaskets have to be installed in a particular orientation to the block, so that water and oil galleries are open to the heads and back again. Installed improperly, and some water/oil galleries to the head are blocked by the gasket.

 

Is this possible in your case? Did you use the proper gasket?

 

Unfortunately, the only way to check, unless you know for sure, is to pull the heads again.

Check to make sure the stat doesnt stick... I had a bad one that I put in. I think my heads were still bad, but I dont think the thermostat helped matters any.

Also, gbhrps post makes sense as well.

Did you do it, or did you have a shop do it?

*** did you properly burp the coolant?  that motor is notorious for air bubbles impeding coolant flow and causing overheating.  make sure you bleed it nose up and get all the air out. 

 

if that's not it:

 

1. what brand headgasket?

2.  were the heads resurfaced?

3.  who did the install?

4.  how badly blown were the headgaskets when the job was done? in other words was this a car you were previously driving, never overheated, or was this an auction special that's been burnt to a crisp?

5.  are both cooling fans coming on?

 

check for bubbles in the coolant overflow, do an exhaust gas in the coolant test, or make sure radiator isn't clogged.

 

car overheats when im not moving but only if driven if i keep it at 3000 rpm in front of my house until it heats up nothing happens and heat temp gauge spikes at 75% before tstat opens

you said the car overheats when youre not moving but only if driven. that doesn't make any sense...