Cuda running warm at highway speeds

[mrob]

Hi,
This past weekend, I had my 73 Cuda 340 on the highway to go to a show about 35 miles away. I noticed that at highway speeds (65-70 mph), the temperature gauge would creep up to about the 2/3 mark on the gauge. This is still within the normal range on the gauge, but it's getting near the upper limit.
Here are some specifics about the car that may help: The 26 in. 2-row brass replacement radiator is about 2 years old and the tubes look clean. There are no visible leaks anywhere in the cooling system. The hoses are about 1 year old. I use a 50/50 mix of coolant with a bottle of water-wetter thrown in. I installed a 160 deg. thermostat when I changed the hoses. At idle or in city driving, the engine runs cool and the temperature stays between 1/3 and 1/2 on the gauge (with outside temperature of 90 deg.).
Right now I'm suspecting overadvanced timing, since the engine runs well with the vac. advanced connected to manifold vacuum and the initial timing set at 15 deg. BTDC. Could overadvanced timing cause the engine to run warm at speed? Any other ideas that I can check out?
Thanks.

[Moparal]

Thermal fan clutch going bad and not locking up
lower rad hose colasping shut
fan belt loose
wrong heat range plugs
carb rich

[mrob]

Thanks, Al.
Going down your list, I don't think it's a loose fan belt, lower rad hose collapsing or plugs with too hot heat range (I'm using Champion RN12YC, stock is RN14YC). Judging by the plug color, I'd say my carb is not jetted too rich. The coloring on the plugs is a light tan color.
Even though the fan clutch was replaced last year, maybe it could be slipping. Does anyone have any suggestions on how to test it?

[Cuda Dave]

It could be to much advance on your timing I would check this could be eazy fix.

[MEK-Dangerfield]

On the Hiway is where air should be your friend. If not a blockage in the radiator, my guess is your water pump.


  Mike

[Bullitt-]

I've read that some thermostats are more restrictive than others & can cause overheating they recommended Molodon or Mr. Gasket high flow. Not very common but the water pump impellers can wear down with age......I'd try backing off the timing a smidge 1st, maybe adjusting the vacuum advance pod to put less total advance in if your using it.

[Chryco Psycho]

it will probably run cooler with a 180 T stat,the water may not be staying in the rad long enough to cool off .  The clutch fan is not the issue , it should be unlocked at highway speed & allowing the air flow to pass through
 simply bending a steel coat hanger into a coil & installing it in the lower rad hose can stop the lower hose from collapsing

[nivvy]

electric waterpumps thy reccomend not using a thermostat... 

[mrob]

Thanks for the responses. Now I have some ideas to go on.

First I'll check the total mechanical advance and make sure it isn't greater than 36 deg at around 3000 rpm. Then I'll check the advance with the vac. advance connected (at 3000 rpm with a Mity Vac supplying vacuum). That total should not exceed 50 deg.

If that solves the problem, I'm good to go. If not, I'll bend a wire and put it inside the lower hose to prevent it from collapsing. The 180 deg. thermostat is an interesting idea and I'll keep it in mind too.

[Bullitt-]

From what I've read the total including vacuum advance should be about 38 deg.

ck this doc.
http://tvmoparclub.com/files/tech/Mopar%20Timing.pdf

[mrob]

Thanks bullitt, that link is similar to the instructions that I found in the archives.

Using a pic that you supplied on a different thread about timing, in which direction should the timing tape be installed? There are 2 possible ways:

(1) TDC mark on tape aligned with TDC on damper and degrees increasing in direction OPPOSITE to engine rotatation.
(2) TDC mark on tape aligned with TDC on damper and degrees increasing in SAME direction of engine rotation.

Here's the pic if it helps to visualize what I'm asking. Remember, the timing marks on my 340 are on the drivers side like your pic shows.

[Bullitt-]

I know that's a trick question ..... somebody help me out here.....gotta be below the line where the arrow is ....then you would reference that to the O mark on the timing chain cover.. 

[mrob]

Can anyone verify that the pic with the timing tape installed is correct for a 340?

Thanks.

[heminut]

I've used timing tapes on every Mopar I've owned. It's correct.

[mrob]

Thanks, 392. Now that I'm sure how to install the timing tape, I can check out my baseline.