[jray1]

I have a 64 gto with a 68 400 in it. New build with a 30 over on the block. I added a Big aluminum radiator big electric puller fan. I have worked the divider plates on the water pump(cast impeller) to very tight tolerences along with directing the rear head outlet (to heater core) back to the passenger side water Crossover and my temp sender is in the driver side. I can't get this car to cool at all. I have flow thru the radiator and I have verified temps with a laser thermometer. The radiator is cool (130-160) and the motor keeps climbing till I hit about 250 and I shut it down. Please tell me there is something I am missing. Also the timing is perfect. Just installed a Holley 750 to make sure I had adequate fuel.

[Garage Goat]

How many miles are on the car?

[68 Firebird]

Garage asked an excellent question. When my motor was freshened with new
bearings, rings and cam and lifters she ran a little to the warm side if allowed to
idle in garage after the breakin was done. As soon aas driven on rode she was cool.

After 100 miles she ran cool even at idle in traffic. Also keep idle up to atleast 600
in gear, keeps lots of oil splash on cam and lifter and helps with keeping waterpump spinning at a good rate.

Also is the water pump pulley smaller than crank? Ask me how i know!!!

Gerry C

[A.J.]

Are you sure the electric fan pulls? Many aftermarket fans have the option to choose pull or push..... and do you have a fan shroud? My experience is that a good working mechanical fan with a thermoclutch works better and pulls more air than an electric one.

[jray1]

It is a fresh build with around 70 miles on it. Fan is pulling air correctly and is in a custom built aluminum shroud to maximize air pull over the entire core. It doesn't cool idling or running down the road. Although the radiator temp is good around 130-160 but the engine will be at 210 or higher.

[My442]

Air in the system

Thermostat stuck shut

Exhaust gas in the coolant

That is where I would look.

[jray1]

I have two 1/8 holes on the sides of the t_stat to eliminate air and have the system topped off with an overflow plummed in to help keep it topped off.

[jray1]

Also its a manual 4 speed and the idle is set at 750-800.

[jray1]

Originally Posted by My442

Air in the system

Thermostat stuck shut

Exhaust gas in the coolant

That is where I would look.

Exhaust gas?

[GoatDr]

If your radiator is that cool then it must be a flow problem from the engine to the radiator. try taking out the thermostat and see what happens. Easy test and I wouldn't recommend not running one.

[72LuxuryLeMansLa.]

jray1,

Do you have a radiator cap that builds 15-16psi into the system?

Karl

[jray1]

Originally Posted by GoatDr

If your radiator is that cool then it must be a flow problem from the engine to the radiator. try taking out the thermostat and see what happens. Easy test and I wouldn't recommend not running one.

Tried that. Same result.

[jray1]

Originally Posted by 72LuxuryLeMansLa.

jray1,

Do you have a radiator cap that builds 15-16psi into the system?

Karl

Yes New cap

[My442]

Exhaust gas in the coolant means that there could be a cracked head. The hot exhaust gas superheats the coolant. There are kits that you can buy at auto parts stores.

Do you have a coolant system pressure tester?

[jray1]

With it being a fresh build and having the heads checked with a complete valve job and refresh I wouldn't think there would be a crack in them. Something I just read on another Site said that there were 2 waterpump gaskets used. One on the timing cover housing followed by the divider plates then the other gasket followed by the waterpump. On mine the divider plates set inside the timing cover housing against a lip and only one gasket was needed. Now I am wondering if the divider plates are wrong or worn down. Any ideas if that might be culprit?

[A.J.]

You say radiator keeps at ~160 and engine rises to 250. How and where are you doing these measurements?

[machota154]

There should be two gaskets. there should be one on the timing cover, then the plate with the same holes as the outside of the cover, then the other gasket and water pump. Also dont forget about the water pump sleeves that go into the timing cover.

[jray1]

Originally Posted by A.J.

You say radiator keeps at ~160 and engine rises to 250. How and where are you doing these measurements?

Infrared shooting at the water crossover where the temp sending unit is and the radiator inlet and outlet areas as well as several areas of the hoses. Done withe the car running.

[jray1]

Originally Posted by machota154

There should be two gaskets. there should be one on the timing cover, then the plate with the same holes as the outside of the cover, then the other gasket and water pump. Also dont forget about the water pump sleeves that go into the timing cover.

Pre 69 doesn't use sleeves unless there is something different about a 68 gto 400.

[A.J.]

I'm not sure measuring this with an infrared unit is reliable. Get a real temp gage and sending unit to ensure you're not chasing ghosts. Or at least compare your measurements on a other engine that runs OK.