I have a 64 dart with a slant six 225 four barrel, with headers on, fort some reason I can not keep her cool, I tried flushing the engine and radiator, I put a shroud on it changed out the thermostat, so one of my questions is what would be the proper temperature for the engine and what should the thermostat be? I have a friend that keeps telling me that chrome valve cover is the problem, any one here anything like that, or could it be the headers causing all this problem.

The chrome valve cover, if it's one of the current-production cheap pieces of junk, might cause problems, but not with engine cooling. A 180° thermostat is usually best; a 160° thermostat is just about never the right choice and will not fix overheating problems; see here (and subsequent chapters accessable at the bottom of each page).

When does the engine heat up? At high speed? At low speed/stuck in traffic? What indication do you have of overheating; is it the gauge heading towards "H", or do you get actual boilover?

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Too many people who were born on third base actually believe they've hit a triple.

I would say at idle, but she doesn't over heat, there is a lot of heat coming off the engine when the hood is open, I do have to say she spit out of the overflow tube when she is running and off trying to cool off.

Headers dump a lot more heat into the engine bay than cast iron manifolds. If you want to keep your engine bay temperature down (which is a nice idea because carburetors and high heat don't play nicely together) go wrap your headers with this stuff.

I think your hot engine bay is a problem separate to your high coolant temperature, but you say the heatup started when you installed headers, so maybe not—try wrapping the headers and see if that cools things back down.

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Too many people who were born on third base actually believe they've hit a triple.

could be coincidence, is that original radiator? Regularly available "engine flush" products won't touch most of the deposits left from over 50 years of use....
may have to take it off and lay it on its back, get some "Super Iron Out" and mix it with water in a 5 gallon bucket, pour it in the radiator and let it sit a while..... flush it out with a garden hose and see what kind of crap comes out.... I'd do this at least 2x and flush with fresh water til it comes out clean, reinstall and give it a go...
Years ago Prestone used to sell a powder flush, was a 2 part system, the 1st stage was the same stuff in Iron Out.... You don't want to create a dust could of the stuff though....

thanks for all the info, the radiator is original but I had it re-cored and sealed.

The original 64 "round top" 19 inch radiator usually has a 2 row core (2 rows of tubes) and those were marginal, even when in good condition.
Any clogged cores, extreme outside temps. or increased engine output can result in over-heating.
You may want to think about having the unit re-cored, using a premium 3 row core or replace it with a better radiator.
DD

thanks but I had that done also, there is a lot of heat coming off the headers anybody ever use that heat tape ?

Header heat will not make the engine run any hotter than having a huge chunk of cast iron hanging on it.

Have you put a temp gun on the upper and lower hoses to verify the radiator is working?

How is the engine running? Is it running on all 6? Is it lean? What is the timing set at? Start with basic diagnostic work instead of throwing parts at it.

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Sounds like you need to remove the bolt on the side of the block and dig any crud that accumulated in there, then do another thorough flush again. Good Luck

When flushing out the radiator and engine, did you include the heater? Did you do a reverse system power flush with compressed air and water? If not take it to a good rad shop and ask them to do the reverse power flush.

Thanks never heard of that but will do

When they do it ask them if you can watch you will be amazed how much gunk comes out. I would recommend 6 liters of antifreeze in the engine after topped up with water and one liter in the overflow. That will help when its smoking hot outside and down to -54 in the winter
Change your thermostat and rad cap. Good time to check condition of all your hoses including the bottom rad hose.

I run headers a four v carb, 195* thermostat, and there is a lot of under hood heat in summer. All that doesn't seem to bother how it runs. Make sure engine is not running lean, and or has retarded timing, both will cause excess heat to be dumped out exhaust, and disallow that thermal energy to be used to move pistons.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC