70 Cuda 340 what water temp should it be running?

[demo0211]

What would normal operating water temp be on my 340 mostly stock 275hp?  Not sure what temp thermostat is in it. My stock rallye dash temp gauge shows close to the top of the middle section of the gauge and spits a few dribbles out the overflow hose after i shut if off.  Is this normal. Starts and runs fine cold or hot.

[Haddixj]

I would get a mech guage to see what temp you actually running until you get confindence in the factory guage and where it reads in relation to the mech one. could be a bad rad cap causing the small overflow also

[Katfish]

Using a inferred gun from HF I got these readings on my 340.  Usually stays below 210.

[Chryco Psycho]

The factory gauges are not overly accurate but it sounds like you are on the high side , could be a number of things causing this , I would confirm temps first , there are numerous threads here covering cooling & things to look for . Thermostat could be a the problem cheap ones can be a problem so you need to know what temp it is rated for & what temp it is opening at .

[joelson6]

put a good (new) 160 thermostat in it. mostly should run between 160 and 180 deg. if not, look elsewhere. do you have a fan
shroud on it? how is the antifreeze? is the water pump working correctly? how old is the radiator? unfortunately there's lots of
factors in why it could run hot. also a bad head gasket  can be the issue, but don't jump to that first..  i have both a
factory and  an autometer gauge in my '74 challenger. but the factory gauge is the standard cluster. when the needle get just
above the first line, it's running at 170 deg. but like previously stated, factory gauges varied.

[unotre]

Try changing the temp sending unit. I just dealt with this problem a few days ago on my newly rebuilt 340. At first I thought it was the thermostat, so I changed it from 180 to a 160 and the temp gauge then showed cooler but still on the high end. The new sender unit I put on was a piece of ****, so I swapped it for an old sender unit taken from a 360 and the gauge reads normal now.

[Chryco Psycho]

I would recommend the 180* but not the 160* , run better & less wear with the 180*

[joelson6]

kind of thought the issue here was the car was running on the hot side and not which thermostat would make it run better.
i recommend the 160 deg. thermostat as a test to see if it helps with allowing the car to run cooler. not to replace it and keep it
in the engine. afterwards you can run whatever thermostat you wish.

after looking at the pics of the gauge and the IR gun, i'm guessing that the sending unit it working fine. my '72 temp sending
unit went bad and it read on the H all the time although the car was at perfect running temp. kind of freaked me out when it
first happened. your gauge doesn't look like it's reading too high.

you really need to look the stuff i listed in my last post and make sure that stuff is good. IMHO.

[demo0211]

Thanks guys for all the info. So far i have replaced the fan clutch and radiator cap and the gauge was slightly lower but still spit about 1/4 cup of antifreeze out the overflow tube into a coolant recovery tank i hooked up until i get this resolved, that was after driving about 15 minutes.  I'm going to put in a new 180 degree tstat and see what that does. 

My assumption is if it is spitting anything out the overflow tube it is too hot is that correct?

Tried a universal mechanical sun-pro temp gauge but realized the temp sender unit in the 340 is a very small opening and can't find a mechanical gauge to fit.

[demo0211]

BTW it is a standard 2 core radiator in good shape with the factory correct stock fan shroud, fan clutch on a std 7 blade fan.

[Chryco Psycho]

yes & no , if it is holding pressure while it is running & only overflows once it is shut off the system is doing its job but I would be nicer to run a bit cooler

[demo0211]

What are the thoughts on drilling a small hole in the outer ring of the tstat before i install it?  I have heard this keeps the system from having air locks.

[Chryco Psycho]

Will not hurt

[joelson6]

there's adapters for the aftermarket temp sensors.. it won't look the cleanest but it will work

[demo0211]

I checked the old tstat i pulled out and it was a 195 degree. put in a 180 and it is running cooler. Think i'm good now. also checked my radiator and its actually a 3 core.