my 1976 f250 is over heating. the radiator is flowing free the thermostat isnt in so its not sticking and my timing is @ 12 deg and the fanshroud is intact. the truck runs great but after i run it for about 15 minutes it starts to get hot. even @ 60-70 mph. Does anybody have any ideas what else to check???

thanks
highrider76

vehicle info
76 f250 highboy
1974 390
1968 gt 4 bl intake
comp 252H installed straight up
holley 650 vac seconday
1 inch carb spacer
Currently running no thermostat...need new water neck
roller timing chain
timing @ 12 deg base

 

hmmm sound like the radiator to me.


but that is just a wild guess.

 

Is it boiling over or is it just the temp gauge showing a high temp? If you're boiling I'd look at the water pump. If it's the gauge showing high then the sensor might need to be replaced.

 

its boiling but i am getting flow through the radiator so I Figured the pump was fine. It was alright before the swap.

 

what ratio coolant are you running, and have you tested the cap? the boiling point of 50/50 coolant under 13lbs pressure is around 24-260 degrees, and a normal engine should run above 212. pure water and no pressure will boil at the hotter end of normal engine temp.

 

I'm just throwing this out there, but when you say swap, you mean you swapped engines or what? If so, had you ran it with the stat yet? You may have some air pockets in the engine and ya may need the stat in there to help them from being trapped in the block.

As I stated, this is just a guess. I'm still a little shadey on your term. "swap"

Mike

 

Before what swap?

I've seen a compression leak into the water jacket that will cause overheating. Incorrect timing and/or running too lean can also cause overheating.

All I can think of quickly besides radiator, pump, thermostat.

Good Luck,

Tracy

 

sorry i meant intake swap

 

the truck isnt running lean i checked the plugs and tuned the carb the other day

 

Is this a new rebuild?

Could it be possible you need a bigger radiator?

Also, if this is a new rebuild, they will make a little more heat than a broken-in motor. Still though, if it's boiling over you have a problem.

How new is the water pump? Water pumps sometimes die slowly.

 

The engine is at least 20yrs old as for the water pump i have no clue how old it is. I put a new cam in it other than that it really hasnt been touched too much other than stated above.

water pumps are cheap so i may throw one on....I hate throwing parts on until a problem is fixed but that sounds like the best solution at the time.

 

you said there's no thermostat, bad idea, put one back in it,without it the water is circulating faster than it can cool, its an exchange system, water heating in the engine, water cooling in the radiator, and then they exchange, and the thermostat controlls this prosess..

 

I agree with hiball, the water has to stop and cool in the radiator. But if this does not help, go with a new pump, you said you did not know how old it is, replace it.

 

Is there anywhere i can get a waterneck to fit the gt intake? the gt intake and the 2bb waterneck hold different size thermostats. I originally bought one but it fell into the intake. the one thant fits the intake doesnt fit into the recessed portion of the waterneck.

 

Drain out the system, put a 180 degree thermostat in it, refill with 50-50 mix water and anti freeze. Problem solved.

You NEED to have a t-stat to control the flow/temp of the coolant. Without it, you will free flow, and then he radiator cant do its job -you gotta keep the coolant in there long enough for the heat to be dissapated out........