need some help to figure this out, i,m startin to lose it !. had the 390 rebuilt, bored .040, new bot end, heads redone, installed new 4 core rad ( cross flow ),new hoses,belts,thermostat (180 superflow),temp. sender, new battery , rad cap ( 13 lbs & tried 7lbs ) problem i,m havin is while driving she runs in the mid range of temp. gauge when i shut it down within 5 min. the temp gauge is pegged and the motor wont even turn over, i removed thermostat and ran for a bit , same thing, installed another new thermostat, 2 -16" electric push fans & removed bush bar ( figured it may be distorting air flow ), checked the timing, AFTER all this the motor still overheats after shut down , , IS there anything i can check or could this be something to do with the rebuild ?

thanx

 

First of all, do you know the actual temperature or just the "the temp gauge is pegged?"

On a warm day (mid-upper 80's to low 90's) my 390 will run at about 185 to 195 degrees (180 degree thermostat) at highway speeds and 195 to 205 at idle in traffic. At shutdown, the temp gauge (mechanical guage) will go up to about 210 and then come back down. This is perfectly normal behavior and nothing to worry about. In a pressurized system, coolant will boil around 230+ degrees, so 210 is no problem. I have seen as high as 220 on a hot day after shutdown.

At these temps the engine is a little hard to start but always does start. I have a Flexi-Lite flex fan with a shroud.

If you are running electric fans, pullers are more efficient than pushers as pushers will block the air flow while the car is moving and the fans may not always run when you are at road speeds.

Does your fan run after engine shutdown? If not, you should wire in a temp switch to let it run until the temp drops to a certain point.

Again, without knowing the actual temp when it is hot, it is hard to tell if you have a problem or not. If the temp goes up to about 220 and then starts coming down several minutes after shut down, you probably do not have a problem.

 

Head gaskets reversed?

Using one of those infrared point-and-shoot thermometers, check the side of the block on both sides - check the temp in the front, and in the back. Should be somewhat close.

 

We could start a club? Make ya feel any better?

 

It could be a "hot" dragging starter....If the end bushing is worn the armature and the field windings get very close when cold, and actually drag each other when all that wire and the armature heat up and expand.....It will start cold/cool just fine, but heat it up and it will crank very slow.......aMP

 

Bingo! The 390 in my Cougar did the same thing although it's not a fresh rebuild. I had suspected the head gaskets were wrong so I removed the AC compressor,brackets etc... to look at the edge of the head gasket. Confirmed it's backwards. Car would do the same thing.....temp was about mid way on the gauge (no numbers on gauge) but when shut down a restarted it would be pegged to hot until it ran a bit and cooled down. You should see a square edge of the gasket sticking out the front of the head on each side. If one side is square on top then tapers in it's backwards.

 

wow! if the gaskets backward then the oil hole going up into the head will be blocked off too right? I have never tried that to see if it would line up or not, no reason to I guess.
also, if the gasket is ok, how is your fuel mix? are you running too lean? that will over heat you bad as well. you must be pinging bad too huh?
and you probably do this already, but Ill mention it anyway. bleed the air out of the block from the heater hose off the intake manifold while filling with coolant.

 

The original poster really needs to supply some additional information. Until then, all of our guesses are just guesses.

 

Ok wait. I looked at mine the other day to check my head gaskets but I wasn't sure exqactly what I was lookin for. If i remember correctly, on both sides, the head gasket is flush with the front of the head/block. Is that right? Also, why does haveing the gaskets backwards cause the temp to peg after shutdown? This has got me wondering about my situation. I'll try to shoot some more pics to go in my gallery and let you guys see what you think about the gaskets.

 

Ok at the bottom of my gallery I've got two pics. One of pass side and one of the drivers side heads. Gaskets are flush. Is that right? I used detroit gaskets also known as corteco gaskets.

 

well, cant tell by the pics. the drivers side pic is good enough to tell that the gasket doesnt stick out in the front. how about under the headers, does it stick out there?

 

​​​​​​I'm having the same problem, less than 1000k on fresh professional rebuild. Starts great, slowly gets up to 175 the electric fans kick on, the 180 degree thermostat definitely works as the temp then drops down into the low 170s initially, but then just keeps creeping up! I haven't driven more than 20 miles at a time because of this,. Around town anywhere from 195 to 212 driving, as I'm putting the car back in the garage, 222 and up!
high flow water pump ( tuff stuff) and matching 180 degree high flow thermostat. Head gaskets are flush on both sides of front of motor and do not stick out under exhaust manifolds. Aluminum 3 row radiator and 3 electric fans pulling 2500cfm. Fitech fuel injection system.
I've switched out the water pump and thermostat again, same result. I use a vacuum tool to refill the system. I also just changed the oil and it looked good. Definitely a knock on driver's side front.
I'm running out of ideas!!!

 

Double check and make sure that your head gaskets are installed correctly. There is a tab that sticks out from beneath the lower front corner of each head if they are installed the right direction.

 

I do have the square corners exposed on the bottom front of both sides.

 

What sort of bore clearance was used when the engine was built?