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Would installing headers and a new larger exhaust increase the temp in my 351w?  After switching out the old stock exhaust manifolds for long tube headers and installing a 2 1/2 exhaust system, my temp seems to rise at times almost to the "H" on my gauge, not all the time but sometimes.  Granted i switched everything out in the spring when temps were a lot lower and now its summer.  I cant figure out why at times the temp seems to be normal and then at others its close to pegging near the "H".  Could this have anything to do with the amount of voltage the system is getting from the alternator at times? 

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I don't think this has anything to do with your new headers and exhaust.  When is the engine temp rising, stop and go traffic, cruising 30 mph or above?  What was the outdoor temp when this happened?  What radiator is in the car?  What thermostat in in the motor?  What type of fan is on the motor?  As you can see, there are several variables.

The motor might be running leaner now with the new exhaust.  Too lean will cause rising engine temps.  So will ignition timing not being advanced enough.  Have you looked at any spark plugs?

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The Temp rises after when i am cruising above 30 mph.  80 degrees was the temp outside. I didnt have this issue a month or so ago.  New aluminum radiator and just replaced the thermostat to a 180 degree.  5 blade fan.  I just replaced the pertronix  ignitor to a new one, took out distributor and put back in. redid the timing.  I replaced a wire on the back of the alternator that had fallen off.  the reason i asked about the alternator is that when sometimes it seems like my temp gauge and my my oil pressure gague are above normal when driving and then will "kick down" after a few minutes.  Could that be from the 3g alternator?

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I would confirm the temp is actually high first. Use a secondary gauge to check the temp.

As you mentioned oil press is high as well it may be pointing to the constant voltage regulator for your instrument cluster.

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4 hours ago, maleah said:

The Temp rises after when i am cruising above 30 mph.  80 degrees was the temp outside. I didnt have this issue a month or so ago.  New aluminum radiator and just replaced the thermostat to a 180 degree.  5 blade fan.  I just replaced the pertronix  ignitor to a new one, took out distributor and put back in. redid the timing.  I replaced a wire on the back of the alternator that had fallen off.  the reason i asked about the alternator is that when sometimes it seems like my temp gauge and my my oil pressure gague are above normal when driving and then will "kick down" after a few minutes.  Could that be from the 3g alternator?

Temp issues like described are often from insufficient circulation.  But, first double check your temps like bigmal suggested.  The reason I say this is I ran a 95 amp 3G alternator for a while.  My charging voltage was always in the upper 14V to low 15V and my oil pressure, temp, and fuel gauges always indicated higher than I thought they should be.  I since switched to an OEM style alternator with external regulator.  Now my charging system voltage dropped to 13.8 to 14.2 volts and my gauge readings dropped down.  I know there is a 5V regulator on the back of the instrument panel, but at least in my case, it seems to work better with the lower charging system voltage.

For the thermostat, I've always used a high flow type.  Mr. Gasket and I know Stewart sells them.  I've had better performance with the Stewart high flow thermostats that have the additional bleed holes.  My personal preference is 160 degree thermostat.  But many like the 180 degree thermostat.  If you put thermostats in hot water you'll notice they do not fully open until about 10-15 degrees above the rated temp.  So you can see with a good cooling system the operating temps will be about 10-15 degrees above the thermostat rating.  Regardless of your preference I would install a high flow thermostat.  I don't know if that will fix your entire issue, but they seem to work better in these cars.

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No change when my headers were installed.

 

I was seeing high temp registering after my new engine was installed. The stock gauges were not giving me a true number and I was getting really nervous in slow traffic. Installing electric gauges gave the true readings. 

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Can anyone tell me were the temp needle should sit when the motor temp is 180 deg.  I have an electronic constant voltage regulator so its adjustable .

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6 minutes ago, Shep69 said:

Can anyone tell me were the temp needle should sit when the motor temp is 180 deg.  I have an electronic constant voltage regulator so its adjustable .

You can not use the needle as an indicator of temp, because it will read differently with an aftermarket sender than with an original one, however, with the orig one, the needle will be around 1/4 up from cold if the sender is working properly.

 

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10 minutes ago, barnett468 said:

You can not use the needle as an indicator of temp, because it will read differently with an aftermarket sender than with an original one, however, with the orig one, the needle will be around 1/4 up from cold if the sender is working properly.

Im not sure what you mean Barney .  I know by adjusting the constant voltage regulator i can see the needles move on all gauges . Im thinking i need to turn it down a bit as my temp needle sits above half at 180Deg and when the fuel tank is full the needle sits way above full . 

 

 

 

 

 

 

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Set your CVR voltage so that when the fuel tank is 1/4 full, your fuel gauge reads 1/4.  From there, your oil and water temperature needle indications will show what they will be for your actual temperature and pressure.  Deviations from those positions will indicate a problem. 

There is no absolute position for oil and water gauges, only relative positions.

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The only way to get some degree of accuracy is to have separate adjustable cvr's for both fuel and temp, fill the tank half full and adjust to half way on the gauge. On a side note if you are running at 180 deg, I feel that you are running a bit cold, as regards to engine wear.

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On 6/23/2019 at 8:20 PM, Shep69 said:

Im not sure what you mean Barney .  I know by adjusting the constant voltage regulator i can see the needles move on all gauges . Im thinking i need to turn it down a bit as my temp needle sits above half at 180Deg and when the fuel tank is full the needle sits way above full . 

The needle does not tell what the actual temp is. Only an infra red gun or gauge with an actual readout in farenheit or celcius will. A non original temp sender will typically position the needle in a different location than a properly working orig sender will when the engine is at the same operating temp, therefore, if the needle reads lower or higher with the aftermarket sender, it does not mean the actual engine temp is lower or higher, so it can be confusing as to whether the engine really is running hotter or cooler etc.

A gauge with a numerical read out is the best way to determine engine temp.

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4 hours ago, unilec said:

The only way to get some degree of accuracy is to have separate adjustable cvr's for both fuel and temp, fill the tank half full and adjust to half way on the gauge. On a side note if you are running at 180 deg, I feel that you are running a bit cold, as regards to engine wear.

The motor has an 180 deg thermostat  Neil. It runs around 190-195 most of the time.  As long as the fuel level is accurate that all what matters . I get what Barney and Midlife is saying.

 

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