Here's the situation:

I just installed a rebuilt 390 in place of the tired 352 in my F100, nothing wild just a stocker (for now ) I'm using the stock 2-core rad with no shroud, 195 thermostat, and a 50/50 mix of antifreeze/water.

Everything's going well, breaking in the cam for about 30mins at 2500rpm, and the antifreeze starts to boil in the rad! So here I sit pondering my options.

1. New 4-core rad, but I don't have $600 right now.
2. Try to backflush the rad and hope that solves the problem until I can try option #1.

Thermostat was installed correctly, upper and lower rad hoses are new with a spring in the lower, so what gives? I realize that engine break in generates more heat, and the lack of a shroud isn't helping but I can't believe a 390 generates that much more heat than a 352.

Any advice you guys/gals can provide would be more than welcome.

 

Maybe you got a tight motor, they generate a lot of heat before breaking in. Do you know what the overbore is? Check the timing and advance too. The 2-core rad has got to go, you need at least a 3-core and a shroud. Did you test the stat in boiling water? Maybe it's sticking or opening late.

Barry

 

I replaced the stat to be sure, checked the timing and found the advance canister was shot. Waiting for a new one, hopefully tomorrow.

I know the 2 core needs replacing, and for a $100 more I'll take a 4-core over the 3, but right now it might as well be a $10,000 'cause I still don't have it. The rad is in the works for the next couple of months.

I'm crossing my fingers that the back flush of the 2-core stocker will at least make it driveable until I can get the new rad. I miss my truck!

Anybody else running a 390 with a 2-core rad? Do I have any chance at all?

 

A shroud is mandatory, especially sitting at idle in traffic. I just replaced my radiator, hoses, etc on my 390 and it stays nice and cool now.

You can pickup a 3-core radiator for $184.11 from http://www.radiatorbarn.com. I didn't see the F-100 in their menu for '67 but they have a radiator for a '68 F-100 with a 390. I don't know if there is any difference between the two years, though. I got a 3-core from them and it fit like the original.

Also, I would check to see if you're running too lean. That can bring the temp up too.

 

$184.11! Must be US. Cheapest I could find here was $500CDN, throw 15% sales tax on that....

 

Yes US dollars. that comes out to 256.56 Canadian dollars not counting tax. And you'd probably have to pay shipping. still a pretty good deal

 

The shroud is a must, and you may find you can even get by with the radiator that you have. A healthy engine makes alot more heat than a tired one, also more cubic inches make more heat. I don't think you would ever need a 4 core if you purchase new. A 3 should do fine. I put a new 3 core on a 72 with a 302 and electric fan. It would have to idle for at least 1/2 hour in 70 degree weather for the fan to even come on.

 

My truck was a 3row with no shroud. When i holed the original rad, I put in a Modine 4 row. i believe it was about $250. I now have a 390, 4 row, and no shroud. I don't have overheating problems, but I'm not breaking in a new motor either. Put a box fan infront of the rad. it doesn't get enough airflow from the engine fan alone when sitting still turning 2,000 for 30 min.

 

One thing I haven't seen mentioned here (maybe I overlooked it)- change your radiator cap. When they become weak and don't allow pressure to build in the system, it will boil over. This should buy you a little time until you can get a larger radiator- and I do recommend you getting one AND a shroud. It'll probably do better sitting still on a cool day with the new cap but it will overheat if you get stuck in traffic.

Joe

 

Thanks for the advice and info everyone.

The stock 2-core didn't handle the reverse flush very well, but after 36 years I'm not surprised so the new 4-core is on order. Oh well, at least with the rad out, I can swap in that new support and inner fenders that have been cluttering up my workbench.

Once again, thanks!