My 78 f150 with the 351m might be over heating I was stoped at a drive through for about 25 minutes at about 15 minutes I notice some smoke around my hood I look at the factory temp gauge and every thing looked ok I thought it might have been some exhaust smoke the wind was blowing up front so I thought nothing of it the truck idled like norma the whole timel drove the 15 minute home ran fine all the way no sign it was over heating stop and get out of the truck and notice the smoke coming out off the hood after I shut the truck off so i lift up the hood and see coolant every were I'm guessing it boild over at some point as all the hoses looked fine I drove it to my mom's about 45 minuts away earlier that day and it had no problems im thinking if its getting hot it might be from long periods of sitting still while idleing the guy I bought the truck off of said he flushed it a few weeks before I bought it but have noticed there is about 4 quarter sized spots in the radiator that have been smashed in would this cause any issues with it warming up outside what else should I be looking at thanks

 

This what the radiator looks like the dents are worse than I thought

 

Do you have a coolant overflow bottle? They're cheap and pretty much universal so you may be able to just get one at a local parts store.

When I got my truck I would top it off with coolant and it would just overflow like you are describing (in the drive-thru a lot). I ran it like that for a year which meant the radiator was often under-filled and it was fine but my heater didn't work great without a full radiator so I installed an overflow bottle. This was good for a few months and eventually I having a properly filled radiator and a normally pressurized system caused the radiator to show it's age so I had to replace that too.

I would start with the overflow bottle and then plan ahead to potentially have to replace the radiator. I went with https://www.championradiators.com/ per recommendations here and couldn't be happier. All-aluminum radiator, quality built, looks great (brightens up the front of the truck being polished aluminum vs the cruddy old painted radiator), and it was cheaper than what I expected. It also comes with the fittings you need to install the transmission cooling lines (if you have an automatic), just don't over-tighten them *they don't need to tighten flush* ...I broke one off in the radiator and had to extract it then find a replacement which turned my 1 hour job into a 2 day job.

 

What size over flow bottle you recommend did you have to make any modifications to install the champion radiator also I plan on putting this 460 in down the road once I get the body and suspention straightened out so if I need a new radiator might as well get one that will handel the new engine to what would you recommend for radiator if I have to replace it

https://www.summitracing.com/parts/hpe-hp19c

 

Someone did a crude solder job on the rad tubes to fix leaks. Time to have it recored, or replace it with a new one.

 

I am with Scott. The wet spots you see on the fins up high and the green all over is a sign it is on its way out.
The smoke (steam) was the coolant weeping out and burning off.

Before you replace the radiator I would do another good flushing as it looks like there is rust sitting in the bottom.
Pull the heater hoses off and back flush the heater core also.
It would be a good time to replace all the heater & radiator hoses and maybe the Tstat & gasket.

My radiator had crust when you looked in side. With it out cap on a laid it flat and filled with vinegar and let sit for a week. Drained and flushed and repeated.
It was in the truck filled with just water and I saw a little puddle and when checking found the radiator was doing the same as yours, weeping.
The crust was plugging the holes, once it was removed it leaked, now has a new radiator and all is good other than that rubber freeze plug (the PO installed) I should have replaced when the motor was out of the truck.
A $2 part comes back to bite me!
Dave ----

 

I ended up pulling the radiator I should have flushed it again before I did but did not think about it at the time I'm guessing was clogged good becouse it took forever to drain and would not keep a steady stream while draining I'm about to order a new one but mine is 24 inches tall total hight and on champion radiators they offer 25 26 and 31 inch radiators total hight for our truck could my truck have an oddsized radiator that someone tossed in?