Wow,, Nice 69.. I have no clue about what would cause it to overheat that way,, it seems like you have hit all of the major points.. Except maybe the
rotation of the water pump.. That could be a doosy..

 

Hell...I dunno, you have the trick Cleveland thermostat. (I went with a block off plate, so I could run a box store thermostat)

Did you check to see if the brass restrictor ring is in good shape in the block?

Also, are you certain that your temp gauge is correct? You may want to borrow an infrared gun from someone, or a different temp sender. I have one for my fluke meter that you could slip under the radiator hose.

Good luck!
Peter

 

Could a blown head gasket cause overheating? Was thinking about replacing them just for ***** and giggles....

 

have you had the block flushed to make sure there is no blockage?

also how old is the water pump, it could be not pumping (fins worn off)

i know youi have a new radiator, but how many rows is it, is it the propper size for a 351 c, my uncle says when went from a 289 to a 351 c he had to go from a standard 2 core all the way up to a 4 core to keep it cool!

 

well it really depends on how ling it takes for it to overheat while idling and at what rate the temperature climbs.. and does it overheat while on the freeway and what is the temperature outside??

give me alittle hints on that and ill help narrow it down for ya


JOSH

 

yes a blown gasket would lead to over heating but through water loss. Also other symptoms present - the ole goey white crap in the oil or rough starting/ rough idle if the water is leaking into the piston(s).

 

Car starts fine, not sure if idling high (no timing light) but loud and smooth. Creates a small moisture pool under exhaust tips when idling.

Temp gauge will crawl around 160-180 for 1-2 min and then spike right to 220+

Drives fine, strong through the powerband - no coughing or smoke. Temp stays pegged while driving (+/- 10deg), regardless of speeds


ambient temps range from 50-70 deg, symptoms are the same regardless of how hot it is outside

 

my vote is timing too advanced i had that same thing a month ago and couldn't fig out the prob but the thing that gave it away to me was that it would backfire throught the carb as soon as i hit 60 mph then i knew it was timing issues i was having

 

todd,,
What offsets are your rims? Im getting some SS's for my 69 and trying to figure which offset I need.. You should check that head gasket ,, If you were thinking about replacing it just for ****s and giggles then do it.. That could be your problem..

 

I would check the water temp with a different gauge than just your dash gauge. I had a dash gauge sensor go bad and it read crazy. I guess my question is, do you really have an overheating car? It could be a sending/sensor unit. Are you loosing antifreeze when it gets hot? You should see antifreeze coming out of the over flow if the system is full and it is overheating.

Troubleshooting:
With the cap off the radiator and the system cool, start the car and look at the fluid in the radiator. When the system gets warm, the thermostat opens, and you should see the fluid start to flow.
If thefluid has bubbles, it isprobably a headgasket.
If thefluid never flows, it is probably a bad thermostat, or a clogged radiator.
If the fluid flows, with no bubbles,check the temp. If it is too hot, check your fan and water pump. You arenot gettingenough temperature transferbetween the fuild and the air. Common causes are undersized water pump pullys and electric fans blowing either the wrong way or not blowing enough air.

I know you just replaced pretty much the whole system, so much of this may not apply, but this is a strange issue. I always like to start from the basics when troubleshooting something.

Just my 2cents.