JayStang65

65 fastback w/289 hipo my step dad did some stuff to it like engine wise but always had a prob keeping it on the kool side -temp wise- my buddy's boss at autozone told me if i dont drive it in the i could take the thrmostat part out like the spring and use the body of the thermostat as like a washer just put it back in the. he said i obviously wouldn't have to worry bout the thermo freezing up and it would have more constant flow, whitch keep engine kooler GOOD IDEA or BAD?

MustangChris04

then your coolant will be constantly flowing. I would just get a different thermostat that would keep the engine cooler

Volcom66

yeah replace the thermo. its there for a reason. you could have buildup between the mani and the termo(very common in old mustangs) and it will not open all the way making it overheat very easy. replace it and see how it works. not an expencive fix but it can do damage if you dont handle it now.

ps: good thought on keeping it open, but the therm. opens at 190 so the water wont go through untill then. making it open at all times can do some damage to the engine, you also dont want the engine to cool because it needs heat to run correctly. good luck

Deannostang

Many times with the older Mustangs of that era, you would run a 185 to 190 degree thermostat in the winter and a 160 degree stat in the summer. One other thing to be careful with in the older hi-performance 289 engines is to be sure you are using the proper heat range plug. All the hypo 289's and 302's used a much colder plug than the standard HP engines. If you are running the standard plugs for a plain Jane 289, you will overheat your engine every time. The true super hypo 289's had solid lifters and used a plug that was about two steps cooler than the standard plug. If you have that kind of hypo engine or not, running constantly too hot can be corrected to some extent by using a colder plug. Good luck!

kalebiscool

richen the carb a little or back the timing up a bit.does it have headers, that helps a bunch.knocked 20 degrees out of my 62 fairlane.