HELP!! Quickly Overheating rebuilt 1968 383 Magnum any ideas?

[Fire Poker]

I did this and the temp continued to rise

 

[2059]

By the looks of your orig. picture you aren't running a shroud. I'd get a shroud, a 7 blade flex fan and a 160* thermostat on it. Even if this isn't the whole problem, It's critical you get that air pulled through the core. Also not a big fan of aluminum radiators, but thats just me. Can we assume it has a new Mopar water pump and not a cheap import knock off. It may very well be a combination of things.

 

[Budnicks]

Possible causes;

cam installed retarded

low oil flow/pressure

faulty water temp gauges, maybe try to temp connect use a differ style & check for comparisons

auto 727 tf high trans temps up heating/transferring heat or to the radiator ???

high ambient outside heat causing heat stacking/soaking in the engine bay

too tight of engine clearances, somewhere in the new parts installed creating excessive heat

retarded ignition timing, especially if the cam is installed retarded

way too lean on the carb main jets
{a 770cfm Holley Street avenger out of the box, is probably pretty close thou, for a mild 383ci}

bad water pump flow or a blockage somewhere

shroud would/could help to draw more air thru the hole core

I have a larger engine & more of a performance build, more camshaft, aluminum heads, 6bbl etc.
I've run electric fans & alum rad. with no issues,
I do have more cfm flowing thou, {supposedly you need about 3000cfm min.}
a Puller fan Perma-Cool 16" #PRM-19115 2950cfm 9.80 amp draw @ 1750rpm aluminum blades
& an auxiliary Perma-Cool 13" #PRM-19113 2650cfm 8.00 amp draw @ 2500rpm aluminum blades pusher
for just incase, it may get hot in traffic or whatever,
a custom shroud 13" fan slightly offset to the upper hose side & the 16" offset to the lower hose side
& use 4 core Mancini Racing Alum 22" radiator,
also a Mopar alum water pump housing
{originally with a high flow water pump & Be-Cool 16" 6 blade alum fan, spaced 1" from the rad.}
& also now have a Proform Electric 37gpm water pump,
I don't have/run a thermostat, I have a 5/8" hole in a restrictor where the thermostat would be,
I made myself out of piece of stainless steel,
I've never had any overheating problems with either set up... making way more power
it'll run at less than 190* all day in Calif. 100* summers

all the electronics are run thru arming switches & all are wired thru relays,
to maximize the efficiency & minimize the draw on the charging system...

I highly doubt it's just because of an aluminum radiator or just because of an electric fan either...

sorry I can't be of more help, just guessing

good luck, either way

 

[Coronet 14]

Could there be air being sucked into the system. Restriction in the exhaust. Dosen't the temprature sensor use the engine for ground. So if you have thread sealant on all the threads it won't make a good ground and cause issues

 

[ragtp66]

assuming the seller was honest I would say you need to go back and recheck the camshaft install and make sure that you accurately check for top dead center with a degree wheel and don't rely on the balancer marks. If it was running good and not overheating before the cam change I would look there first. The fan/shroud really doesn't matter once your rolling the airrflow from the car moving should be enough to keep it cool.

 

[Hemi Rebel]

Here is what i would do. First thing is to hook heater core back up. Then I would fill the system. Running the engine with the rad cap off till the t-stat opens. With the system full and the engine idling you can feel the upper and lower hoses. They will be hot. Air being pulled through the radiator will be hot too. You should be able to feel the obvious change in temp of the air and hoses when the stat opens. If all this checks out and the temperature is ok then I go for a ride. If the temp starts to creep up when driving then turn the heater on. That should help dissipate heat. If the air from the heater is not hot you either have circulation issues, a blockage, or an air pocket. Typically what you will see with a head gasket leaking compression into the cooling system will be wild fluctuations in temperature. It will go high, then come way down and then go back up. And coolant will be pushed out. How is the rad cap btw?

 

[Basket case]

what kind of temp gauge? If not using a manual, get one, if just for piece of mind.

 

[71airgrabberRR]

I would do as Hemi Rebel asked. One time I had a similar problem when I built a nice 383HP and dropped it in a 77 Cordoba. I went through everything as have you, but the first thing I replaced was the radiator. Nothing fixed it. I was so angry that I pulled the engine and replaced it with a nice street able 440 that I had also just built. Even after replacing the ENGINE, it still got way too hot. In desperation, I pulled the radiator back out and took it to a radiator repair shop.

Come to find out that most of the lower core openings were soldered over and wouldn't let the coolant flow properly. Never in a million years would I have expected a NEW radiator to be defective, but it was. It was never visible until the lower radiator tank was removed.

Never think that just because something is new that it will always be "good".

Hope this helps.

Please keep us posted.

 

[Basket case]

when I worked at the IH dealership, we went thru boxes of "New" starters and alternators to find a good one.

 

[71airgrabberRR]

Another problem I once had was with a new water pump. At room temperature, the impeller was tight. Once heated to operating temperature the impeller expanded just enough to slip on the shaft while trying to push the coolant through the system.

This was another once in a million chance. I replaced the water pump under warranty and problem solved. It was another classic case of a bad "new" part.

 

[RS23VOA]

I read a thread about the water pump housing being too restrictive causing major overheating.. Don't know if you're running an aftermarket housing or not.

 

[Richard Cranium]

retarded ignition timing, especially if the cam is installed retarded by a retard

Fixed.