[bocephus86]

i just rebuilt a 90 model 350 40 over just got it put in and i run for about 3 minutes
and it over heats bad i work on this stuff for a living but this prob is new to me
also i have no stat in yet

 

[Jon]

This wiki article may be helpful to you: Bulletproof cooling system.

 

[Frisco]

i just rebuilt a 90 model 350 40 over just got it put in and i run for about 3 minutes
and it over heats bad i work on this stuff for a living but this prob is new to me
also i have no stat in yet

The most often cause of a new engine overheating that quickly is because the timing is retarded. Check this first.

Dis-connect the vacuum advance hose from the vacuum advance cannister and plug the hose. Restart the engine. Bring the RPM up to 2500-3000 RPM and check/set the timing in the 32-36 degree range. Re-connect the vacuum advance hose.

Install a 180 degree thermostat. Running without a thermostat or some other restriction can also cause overheating because the coolant is able to flow too quickly thru the radiator and thus does not get enough time to cool.

If you have a clutch type fan, it will not be very efficient at higher RPM's that are run during the cam "break-in" period and will not help cooling a stationary vehicle. Place a "box" style fan in front of the radiator to assist the cooling when running the engine during the cam "break-in" period.

Installing a fan shroud will help.

Running straight water with no anti-freeze will cool best.

If you are running a flat tappet cam, continue to run the engine between 2000-3000 RPM for about 20 minutes. This is to "break in" the cam. Vary the engine RPM some to help "splash" oil onto the cam during this time. Watch for any coolant, fuel and/or oil leaks. Watch the engine temps and oil pressure. Shut down to fix if required, then restart and continue the "break-in" procedure.

Change the oil and filter immediately after the "break-in" run. Re-start the engine. After it reaches full operating temps and the choke is fully open you can begin to adjust the carb if necessary.

 

[sunsetdart]

If you filled the system up by just pouring the coolant into the radiator, then waiting for it to go down and then filling till it's full,you probably chased an air bubble into the system. I work for a cooling company and I tell all my customers that when filling up the system, fill through the neck on the manifold. That way you fill from the bottom up. You pour about a gallon and a half into the block, then put the neck back on then refill the rest thru the radiator.
The only way to get that bubble out is to get the motor hot, let it cool and keep doing that ...eventually you will get that bubble out. It has to work it's way to the neck and out to the radiator. You're actually bleeding the system.

 

[bocephus86]

thanks for the input i was in a rush as always but i left out one part
i have some where around 81-84 heads on this 90 model block the heads are # 376450 nothing great about them best i had on hand
i dont have alot of $$$$$$$$$$$$ to spare anymore due to kids,house,oldlady lol so im using what ive got any one know if there is probs with these heads on this block maybe why is heating so quick thanks to all

 

[sam_bo3]

when bleeding your cooling system. Turn on your heater it so you cycle water through the heater core as well. If the radiator cap is lower than the manifold it is easy to trap air. You can jack up the front end of the car so the rad cap high point of the system. or get on of these

http://www.denlorstools.com/home/dt...2150_coolant_funnel_w_radiator_fill_adap.html (they can be had for cheaper than this) They are also a good diagnostic tool. YOu can see the exhaust bubbling out if you have a bad head gasket.

 

[bocephus86]

when bleeding your cooling system. Turn on your heater it so you cycle water through the heater core as well. If the radiator cap is lower than the manifold it is easy to trap air. You can jack up the front end of the car so the rad cap high point of the system. or get on of these

http://www.denlorstools.com/home/dt...2150_coolant_funnel_w_radiator_fill_adap.html (they can be had for cheaper than this) They are also a good diagnostic tool. YOu can see the exhaust bubbling out if you have a bad head gasket.

i dont see any probs with a air lock in the system im not running a heater
core at this point ty

 

[Blazin72]

You make no mention of how hot the engine actually gets. What temp is it reading? What type of gauge do you have?

 

[T-bucket23]

Running straight water does cool the best, however if you don't put a anti-corrosive additive in it you will destroy the engine with rust in a very short time. Running straight water also lowers the boiling point of the coolant so you will loose a little protection from boiling over.

Not running a heater core can disrupt the cooling effectiveness insome setups. If you still have a heater core in the vehicle I would try it with it connected, if not you could try a piece of heater hose looped where the core would normally be connected to see if it helps.

If you can feel the top hose and it is hot (be careful) then the thermostat is opening and air should not be an issue.

 

[bocephus86]

You make no mention of how hot the engine actually gets. What temp is it reading? What type of gauge do you have?

its a 86 chevi 4x4 its has lights no gauge which i hate
im planning to install gauges at a later point my be sooner now due to this prob i know heating because after a few minutes running the water will start to blow out the radiator as far 1 foot high with lotts of steam and not from water on the exhaust ethier
ty

 

[ericnova72]

Do you have the correct water pump for the type of drive pulleys that you are using?? V-belt rotates clockwise looking from the front, but a serpentine belt pump is made to rotate counterclockwise because it uses the backside of the serpentine belt to turn the pump. If you have a '90 pump and '86 pulley set up it will overheat in a matter of minutes.

 

[bocephus86]

Do you have the correct water pump for the type of drive pulleys that you are using?? V-belt rotates clockwise looking from the front, but a serpentine belt pump is made to rotate counterclockwise because it uses the backside of the serpentine belt to turn the pump. If you have a '90 pump and '86 pulley set up it will overheat in a matter of minutes.

im using the the pulley set that came with the engine and it was in a truck that was being used
i thought about that also but idont know of it having heating prob before
ty

 

[ericnova72]

im using the the pulley set that came with the engine and it was in a truck that was being used
i thought about that also but idont know of it having heating prob before
ty

Where did the water pump come from?? Can't use a v-belt pump with serpentine pulleys or use a serpentine pump with v-belts. '90 truck would originally be one belt runs everything serpentine w/reverse rotation waterpump, '86 truck would be a v-belt or maybe standard rotation short serpentine/v-belt combo.

 

[bocephus86]

i later found that i was getting water in my oil so pulled the heads and had them shaved
i got every thing put back together and ive ran the engine for about 4 hours with no probs
yet
thanks for everyones input