I have a 1978 F250 custom with the 300 straight six in it. The radiator on it needs to be replaced however I'm having trouble finding one the same size as what's in it. All the websites I've checked only have them for the v8 and the few I've seen for the I6 are 6 inches wider than what's installed. The current radiator has a core size of 18 3/4 wide x 18 1/2 height. Anyone know if this is even the right size for this engine or where to find a replacement?

 

Welcome to FTZ Sekournen. As a first suggestion, do live in a town or near a town that has a radiator repair shop. If so you have the option of having your radiator Re-cored. You might be able to have a core installed with another row or two of tubes added for better cooling. Also you would have what looks like the original radiator by using your upper and lower tanks.

Second, the correct replacement radiator should be available. If the truck has a Ford Radiator now, look for #'s on the top tank, it would help finding a correct new replacement. Post the # here.

Let us know how you make out, Cap

 

Unfortunately I don't have a repair shop anywhere near me that still works on radiators. I went out and checked all over the radiator and the only numbers were a plastic tag in the core that had GRAIG on one side of it and 393472 on the other.

 

Check out this site, especially the 5th radiator down. There are narrow and wide radiators for the 6

https://www.radiatorexpress.com/part-lookup/radiator/ford/1978/f-250/base/49l-l6

Don't know about your year and model but, on some trucks the radiator support frame has a narrower window for the 6 than the V-8 and you will see a set of holes toward the drivers side for the bolt clips the rad fastens to. If your happy with finding a direct replacement that's good. You can go to a larger (wider) rad if you want to.

This was my search, much to look at especially for best pricing.

https://duckduckgo.com/?t=ffab&q=1978 Ford F-250, 300 six radiator&ia=web

 

I have ordered a new core before and and used my tanks use some good solder and then pressure check it in water

 

1978/79 F100/250 300 I-6 with a manual transmission and standard/xtra cooling: D9TZ-8005-D .. Radiator /18 5/16" high x 18 29/64" wide / Obsolete

CARPENTER NOS PARTS in Concord NC has 1 = 800-476-9653.

The only alternative you have, is having your present radiator recored.