68 Dodge Charger 440 Running HOT

[Charger68RT]

I have a 68 Charger RT that is overheating. 440 original Motor was rebuilt 2 years ago and I have tried everything to fix the problem.  Motor was rebuilt as close as possible to stock.  No crazy cam.  I have re-cored the radiator, replaced cap, thermostatic, water pump, removed water pump housing and ran water through the block with garden hose with no blockages.  Only a few hundred miles on the new motor.  4 speed car with AVS carburetor.  Car has CAP package and mechanical timing is set at "0" TDC as designated in Dodge manual.  Car will run 10-15 minutes at idle at 170/180 and then start to creep upward until I turn the car off at 200/210.  Getting warm is proportional to outside temperature.  I have completed a compression test and all cylinders are good. The plugs are showing some black carbon deposits.  I assume this is related to the extensive idling I have done trying to correct the issue.  Once the motor gets warmer it will experience post ignition run on and dieseling.  On a cool day when I drive the car, running at 50  to 60 MPH will not cool down the temperature of the water.  Running at fast idle I can see the water being pumped through the radiator cap.  Out of ideas.  Questions:  I have read that newly rebuilt engines will run warmer until they are broken in.  How many miles does that take?  The motor does turn over and start without any big delays.  I have also read that carbon deposits in the pistons/heads will cause the motor to run hotter?  Could this be related to a carburetor adjustment?  To rich a fuel mixture?  Appreciate everyone's help and feedback

[70 sublime]

Did the motor over heat before you did anything to it ?

Did you change the water pump for exactly the same one with the same number of fins on it ?
Change any of the pulley sizes ?

[WHITE AND RED 69]

Play with the timing. Set it up at 12 degrees BTDC and go from there.

[Charger68RT]

Did the motor over heat before you did anything to it ?

Did you change the water pump for exactly the same one with the same number of fins on it ?
Change any of the pulley sizes ?

When I bought the car it ran warm.  The freeze out plugs leaked and the car had a low pressure radiator cap on it.  When I had the motor rebuilt I had the original water pump rebuilt as well.  I replaced it with a "Gates" water pump.  Both pumps have 8 blades/fins.  I have not changed any of the pulleys. Thanks for the feedback     

[Charger68RT]

Play with the timing. Set it up at 12 degrees BTDC and go from there.

I have disconnected the CAP "Clean Air Package" which is disconnecting and bypassing the "Distributor Vacuum Control Valve".  When bypassed the ported vacuum goes directly to the vacuum on the distributor.  I then tried running the car timed at 12 degrees BTDC.  Not much of a difference.  The motor stills gets hot.  I'm not crazy about the CAP system as it recommends you set the timing up at "0" TDC.  I have vacuum tested it and it seems to work fine.  Thanks for the feedback         

[birdsandbees]

200/210 is not hot, especially sitting idling in one spot!

[68CoronetRT]

Yea, 200/210 is not that hot. Mine runs about 170 when cruising and like 200-210 if it idles for a while. It drops quick once you get moving.

2 Row, big tube aluminum radiator, water kooler water pump, 10 lbs cap, custom built fan shroud and a 7 blade metal clutched fan. Fan shrouds are the key to cooling.

Timing can play a factor also. My idle is at 16-18 ish degree's. Cranking is 12 degrees.

[Charger68RT]

200/210 is not hot, especially sitting idling in one spot!

It runs up to the top of the normal range of the gauge and I turn it off.  I guess that would be about 230 degrees. When I turn the car off the temperature continues to rise. It then blows some anti freeze out of the radiadiator overflow tube. I then sometimes I get post ignition/dieseling when I turn the motor off. How hot can you go before blowing the head gasket?  Thank you for the feedback.

[Charger68RT]

Yea, 200/210 is not that hot. Mine runs about 170 when cruising and like 200-210 if it idles for a while. It drops quick once you get moving.

2 Row, big tube aluminum radiator, water kooler water pump, 10 lbs cap, custom built fan shroud and a 7 blade metal clutched fan. Fan shrouds are the key to cooling.

Timing can play a factor also. My idle is at 16-18 ish degree's. Cranking is 12 degrees.

It NEVER runs at 170 degrees. Once started it runs up to the top of the operating scale. Even cruising down the road at 60 mph it does not drop all that much. I'm a stickler with originality and the motor is all stock. I don't want to change the shroud or the fan. Thank you for the feedback. Appreciate the help

[nchrome]

l know this may sound wrong to you but do you have a temp lazier. Just a dumb idea check temp at each frost plug. l know ya trust your machine shop but ya mite have an old frost plug in the water jacket on the block.  Don't laugh it has happened to me in the past  That was after l replaced the thermostat, water pump, rodded radiator, took out ac condenser, then someone told me to look at each frost plug and pull it and take a look inside.  Guess what l found for back then the price of a few frost plugs l ended up with  eight frost plugs . and no more over heating. JUST A SUGGESTION   

[c00nhunterjoe]

The factory gauge may not be accurate. Check with a mechanical one before beating your head against the wall. Dieseling can be heat build up in the carb and too high an idle with the ethanol fuels

[Mopar Nut]

Check the block temperature with a infrared temperature gun, you could have a defective temperature dash gauge.

[JB400]

What fan/ radiator setup do you have?  If you have the fan clutch setup, the clutch could of went out.  Also, not having the fan close enough to the radiator could cause you issues.  Not having a shroud, could cause you issues.  If you're running an electric fan setup, your fans could be running the wrong direction, or not working at all.

[XH29N0G]

I was also going to ask about the Fan set up.  On mine, I had high temperatures with a clutch fan and I replaced the clutch and they dropped dramatically.  I suspect the clutch must have just worn out, but I do not know enough to know how. 

[Charger68RT]

l know this may sound wrong to you but do you have a temp lazier. Just a dumb idea check temp at each frost plug. l know ya trust your machine shop but ya mite have an old frost plug in the water jacket on the block.  Don't laugh it has happened to me in the past  That was after l replaced the thermostat, water pump, rodded radiator, took out ac condenser, then someone told me to look at each frost plug and pull it and take a look inside.  Guess what l found for back then the price of a few frost plugs l ended up with  eight frost plugs . and no more over heating. JUST A SUGGESTION   

As time goes on I suspect some type of blockage in the block or heads.  I have no faith in the machine shop I used. It was suggested to me and a year later they went out of business.  The car was a barn find and spent about 25 years in storage.  If it is an internal blockage I would assume you have to tear it down and start over again.  I do have a laser temp gauge and will check the freeze out plugs.   What if the plugs were two thick?  Could they be in too far and blocking water flow?  Thanks for all the information.  I appreciate the feedback.

[c00nhunterjoe]

Again, start with the basics before you start panicking. Verify the gauge 1st. Then start checking water temp in and out of the radiator. And do not forget, a "180" thermostat does not mean the car runs at 180. That is the temperature it STARTS to open. On average, it takes 20 additional degrees to reach full flow. So your running at 200 is acceptable with a 180 stat.

[Charger68RT]

Again, start with the basics before you start panicking. Verify the gauge 1st. Then start checking water temp in and out of the radiator. And do not forget, a "180" thermostat does not mean the car runs at 180. That is the temperature it STARTS to open. On average, it takes 20 additional degrees to reach full flow. So your running at 200 is acceptable with a 180 stat.

You are correct. I need to get a separate mechanical gauge to verify the accuracy of the stock gauge.  A temp of 200 being normal makes me feel a little better.  I'm just always nervous about blowing a head gasket. Thanks for the help and feedback. 

[1970Moparmann]

Get a laser temp gun and keep going down the line.    Write down each temp as the engine runs longer.

My 68 Charger had a restrictive water pump housing on it.   There is a thread that talks about the 400 source bad batch of housing and a bunch of us had one.   The other aspect that I learned the hard way was there are two different gauge readings that you can get.   As in the numbers are in two different positions compared to the needle.   Like someone said, if you put on a secondary mechanical gauge this could help also. 

My Coronet, it was the same situation as your to a tee.   Years and years of it getting hot wound up being a clogged radiator.   Even though I had a re-cored radiator when I did the refresh on the car, it still was clogged and caused it to run like your car.    I bought a YearOne aluminum and it has been fine since then.

[Charger68RT]

Check the block temperature with a infrared temperature gun, you could have a defective temperature dash gauge.

Agreed. I'm going to get a mechanical gauge to verify the stock gauge. Where is the best spot to laser check the temperature on the block?  I have been shooting it right where the ware temp sensor is screwed into the housing. Thanks for the feedback and help.

[strokie451]

I use Waterwetter in my 451 ci 11.1 c.r. with 22 inches rad with shrould , never had overheating problems...
The trick to drop temp is more use of water = less heat in the engine.
antifreeze is not the best to cool engine.
during summer you don't need antifreze...

[c00nhunterjoe]

Check the block temperature with a infrared temperature gun, you could have a defective temperature dash gauge.

Agreed. I'm going to get a mechanical gauge to verify the stock gauge. Where is the best spot to laser check the temperature on the block?  I have been shooting it right where the ware temp sensor is screwed into the housing. Thanks for the feedback and help.

Check at the fitting for the gauge sender.
Check radiator inlet temp, check radiator outle temp. That will tell you how well your radiator/fan is working.

[Charger68RT]

What fan/ radiator setup do you have?  If you have the fan clutch setup, the clutch could of went out.  Also, not having the fan close enough to the radiator could cause you issues.  Not having a shroud, could cause you issues.  If you're running an electric fan setup, your fans could be running the wrong direction, or not working at all.

The fan, shroud, radiate, and fan clutch are all stock. I double checked and the fan has 7 blades like it is suppose to. I changed the fan clutch with a stock aftermarket just to be sure.  I will put the Dodge one back on when I get the heat issue resolved. Than you for the feedback. How close should the fan blades be to the radiator?  Less than 1 inch?

[INTMD8]

The factory gauge may not be accurate. Check with a mechanical one before beating your head against the wall.

Agreed

[JB400]

What fan/ radiator setup do you have?  If you have the fan clutch setup, the clutch could of went out.  Also, not having the fan close enough to the radiator could cause you issues.  Not having a shroud, could cause you issues.  If you're running an electric fan setup, your fans could be running the wrong direction, or not working at all.

The fan, shroud, radiate, and fan clutch are all stock. I double checked and the fan has 7 blades like it is suppose to. I changed the fan clutch with a stock aftermarket just to be sure.  I will put the Dodge one back on when I get the heat issue resolved. Than you for the feedback. How close should the fan blades be to the radiator?  Less than 1 inch?

About an inch

[AKcharger]

I had a very similar problem with my '72, recored radiator and all. The issue? Mice made a home in part of the core while it sat waiting to be installed. If radiator sat for a while worth looking for junk in the radiator.