ok here's my story. ok when i bought my 69 mustang it had a 302 with a 2-row radiator... once i got it to my house ( central valley, ca) where the temp is over 100 for most the summer it would heat up no matter where i drove it. so i bought a new 4-row rad and at the same time i swaped in a used 351 windsor, ( i didnt know it at the time but the windsor was actually bored 60 over) however it ran cool. in the middle of summer 100+ temp i could let it idle for 10 mins and it would never overheat.

the windor started to smoke after about 6 months of driving it so during the winter i bought a new short block (everything stock) used the same heads, manifold and carb, headers, exhaust. once i got it runing i noticed it would run pritty hot. if i drove it under 25 mph it would continue to get hotter and if i let it, it would of overheat. if i let it idle, the needle would continue to slide to the H and would be there in roughly 2 min, so pritty fast. even on the hwy it would never run as cool as the first windor.

so put a new high volume water pump, changed the themastat from a 180 to 165 so it would open fast, i put a higher psi rad cap. nothing helped. i know i could probably buy a new alum rad with elec fan system but what bother me is the only thing to change during this whole senerio is my engine... all the common denominators are the same execpt the engine.

could there been a cooling port blocked inside the engine? at this time im out of ideas... help!!!!

 

What is the top temp of the rad vs the temp at the very bottom of the rad?

Where in central valley are you? Fresno by any chance?

-Gun

 

What fan and shroud do you have now? Have you installed a shutoff valve in the heater hose?

 

New rad plus old engine - did you install a filter? If an engine has been sitting around the block will be slowly rusting. Once you start running hot water thru it you end up with chunks of old rusty scale and crud coming loose and slowly blocking your new radiator.

did you tank clean the old heads before you put them on the new short block? Was the new block actually "new" or new to you.

you might need the 4 row radiator cleaned out and rodded and I'd strongly recommend a tefba or similar filter in the top radiator hose.

 

im not sure of the different temps at the top an bottom, i dont have one of those temp guns, i live in visalia 35 mins south of fresno.

2+2gt-i have a 5 blade flex fan but i dont have a shroud. i know i should have one but it never needed one before. and no shut off valve

aussie- i dont have a filter and that did start to happen, however when i bought the new short block (brand spankin new) i had the radiator taken down to the local radiator shop and had it cleaned and rodded. i even replaced the sending unit thinking that it was faulty. and yes i tanked the heads and had them rebuilt as well.

im really stumped on this one guys

 

ok, are you just running the in-dash gauge? do you have any spare holes on your inlet manifold or thermo housing where you could install a mechanical temp gauge as a backup to confirm your readings?

part of this is almost certain to be more hp = more heat now you've fixed the engine up.

other areas...
+1 a shroud would help.
Are you confident timing and mixtures are all ok? eg if you're running lean you will run hotter.
thermostat is correctly installed? (i'd go back to a 180* but test it before install to make sure its opening correctly.)
what state is your heater core in? (I rodded the radiator and didnt clean up the heater - replumbed and filled the clean cooling system with muck from the heater. Doh.)
i still reckon its worth installing a radiator filter - even one of those socks that go in the top hose will soon tell you if blocking is an issue.

are you loosing any coolant?
do you have a recovery system or straight to ground?
what sort of coolant are you using - correct mixes etc?

sorry to pile on the simple questions but its often a simple issue or combination causing the problem. keep it coming!

 

Yeah I lived in 3R for many years...Ill be heading there maybe the middle of this week. I could have a looksie when I pass through and bring my temp gun if you are down for that.

-Gun

 

and take that elephant cannon in your sig pic with you...just in case you have to put his car down :P

 

im not sure when you will be passing thru here or how often you pass thru here but maybe next time, due to my work shift time... amd if i knew alitte more in advance i actually left it at my pops house since he has an endless suply of tools.

aussie- yes im runing the in-dash gauge, ill have to look tomarrow to see if i have an extra opening
-timing and mixture, im not good with timing so i took it to a mechanic shop and had them set it.
-thermostat is correctly installed and i put it into boiling pot of water to make sure it worked and had a thermometer there as well to make sure it opened at the right time
- my heater core was actually replaced a few months after the engine was replaced.
- i dont have a recovery system, and now im running straigt h20 because of the over heating kept pushing out all the coolant i was runing 50/50 until it got deluded from me having to add water every day

do u think having a fresh short block would make that much more hp then the old beat up one to cause this much more heat?.. i mean i did transplant everything else from the old to new...

 

Can you confirm from the shop if they reset the mixtures? If it is lean, it wont be helping and could be a significant cause. You could try pulling a plug and having a look at its condition. Take a pic and post it.

without a recovery system, your radiator will always push out the top 1" or so due to expansion as the coolant/ water heats up. But it will stabilise at about an inch low and should only needing a little top up from time to time. A good coolant mix is a must for temp and (especially in these old cars) corrosion control. Ideally mixed with RO or distilled water.

new engine = more hp (even if little else is changed) = more heat. BUT i dont think that's your issue here.

what psi cap did you change to?

what water pump did you get...its probably unlikely but there was a post recently on someone who'd put a reverse rotation water pump on the car and was overheating because of it.