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1/01/2021 5:07 PM  #1

1966 Mustang Coupe 24" Radiator Upgrade

1966 Mustang Coupe, 5.0 Swap, EFI/MAF, T5z
Radiator: Dewitt Radiator[u] Model: 32-4138006M  [/u]
Natural/Manual, Made in USA, Dual Fans, 24 inch, designed for 1968-70 Mustangs.

This was pretty straight forward.  I wanted the 24 inch radiator and the only real complication was getting the thickeness down in the center to clear the water pump hub.  There's several write ups for this effort so I'll just focus on what I did different and unique to my setup.  This isn't so much as a how to as general notes.

1) I had relocated my battery to the trunk several projects ago so that wasn't an issue for me.  If your battery is in the stock location you may have some interference.  The dual relays for the fan were wired in this general area.

2) The opted for one of the nice billet alluminum radiator caps from Dewitt.  I didn't realize till after the install that these were about 3/8 inch thicker than a universal radiator cap.  I did a clearence check with some clay and I only have maybe 1/4 inch clearence between the hood and the radiator cap.

3.) The cut out is simply taking about 2.375" from either side of the stock opening on the fender wall.  A stock radiator is actually offset about an inch to allow for more space for the battery.  So if you center your radiator based on the cap, it will acutally be offset to the left looking in to the car.  Taking a tip from another write up, I split a 1/4 inch radiator hose and used it for trim on the cut edge.  Looks pretty nice.  On the bottom where bottom edge where the radiator sits, I took some real thick rubber gaskert material and used it as a buffer for the mounting service.  I tried the lower radiator mounts but couldn't get them to fit.  On top of that, sitting the radiator on the stock mounts would have increased the height and likely interfered with the hood.  I didn't take off the front end or use any special tools.  I was able to make a clean cut with a grinder and flywheel and dremel.

4.) I considered getting creative on the top radiator mount but the stock mount really is the best way.  To simplify install, I modified the top radiator bracket with some weld nuts and just match drilled the clearence holes.   Made the top part super easy to take in and out.  I just went to a muffler shop and had the guy weld them in, 10 minutes, $10.  It did result in the hardware being slightly offset because I centered the radiator but none of it is visible under the hood so doesn't matter to me.  I did have to grind the stock rubber bracket pads down to get them to fit and even then the bracket took some massaging to sit correctly when installed.  I just bent the bracket down and did a fit check incrementally until I got a good fit.

5.)  As mentioned, the lower radiator brackets for 67-69 wouldn't work.  So I had to find a way to secure the lower radiator.  Because this setup came with a fan and shround combo, I opted to run a 1/4-20 UNC rod through the shroud, fins, and render wall to secure the lower radiator.  The engine side of the radiator has a castle nut for asthetics.  The nut that isn't visible on the headlight side is simply a locking nut.  I used a fender washer stackup and it's great.  I used a 3/8 aluminum precision rod I picked up from amazon as a long bushing.  VERY secure.  I didn't have any exact way of getting the sizing right for the bushing.  Just cut a little long and test fit and round it down will it was right.  Keep in mind this is aluminum sheetmetal, if you secure anything with steel hardware over torquing it will result in deforming the sheetmetal.

6.) Upper hose was an easy install.  I used the lower radiator hose from the Bronco II.  I had to trim about an inch from the down port end coming off of the thermostat.  Other than that it was clean fit and looks stock.  The lower hose was another animal.  I went thorough several stock hoses trying to find a fit and then attempted to cut a hose to fit which nearly resulted in me making an ER trip.  In the end, I settled on a flex hose.  If I had to do it again I would order some proper metal inserts designed for joining hoses.

7.) I had to buy a shorter fluid overflow resevoir.  I wanted to install it on the oppostie side where I had the relay wiring just incase.  However, the port from the radiator cap pointed the opposite direction.  I ended up running a much longer than I wanted hose down and around the bottom of the radiator.  It's not visible and I haven't seen any fluid actually coming out but I wanted one just in case.  Something else to keep in mind.

1.) I did a radiator flush with the old radiator installed before I did this effort.  I did this so I could sell the old radiator as having been cleaned (although still for sale) but also so that any of the build up from the block wouldn't settle in the new radiator.  Speaking of fluid... don't waste your money on the fancy stuff.  The generic 'all models' coolant is fine.  If doing a new install which obiviously requires using new fluid, DON'T BUY 50/50.  It's a huge waste of money.  Buy the concentrate and then go over to your local grocery store and by a couple of gallons of distilled water.  You literally save half the cost on the fluid.  If you buy the 50/50 mix you are just paying for water!  Either way, be careful potentially dealing with hot coolant.  Water boils at 225 degrees but coolant buy design will go higher than that.  

2.) This is obviously a unique setup.  I could have gotten by with a 20 inch radiator and if you go with a smaller size you may want to consider the proper opening.  A 24 inch radiator covers the full opening.

3.) I live in Dallas County, Texas so fluid disposal is covered by the city.  Alwas properly dispose of hazardous fluids.  For me it was just drive up, hand them the jugs and drive off.  Autozone, Pep Boys, Oriely's typically only take oil, not coolant.  

4.) I didn't remove the from bumper and headlights but every other write up recommends that.  I have a 5.0 with no A/C, now power steering, so there is a bit more room.  I also specifically sought out a radiator fan combo with less than 6" thickness.  You may have to remove components to gain access.  

5.) You will need one relay for each fan but the keyed on ignition wire can be spliced to both relays.  In order for the fans to work you need a constant 12v source AND an Ignition Power source.  The ignition power source doesn't power the fans, just toggles the fans on and off.  If you were to connect the Keyed On wire to a constant source the fans would work but then they would stay on even after the car is off until the radiator thermostat switch met the off temperature. 

6.) This radiator came with a 185/195 switch installed on the actual radiator.  I had previously had a 175/185 switch installed on the thermostat housing.  Both will work.  I went with the higher temp switch.  

7.) The total thickness of this setup is more important than the width.  Verify with the manufacturer!  Don't want to spend a bunch of money only to realize it won't fit.

I realize there are cheaper options but I wanted to buy American on this one so I paid a premium.  I called Dewitt tech support once to verify sizing before purchase and once during the install to verify the relay wiring.  Both times they were helpful.  I picked up the entire radiator kit for $800 on a Black Friday sale and that included taxes and shippping.  Summit Racing has this same setup for sale right now at $839 plus taxes.

Other items...
1967 FORD MUSTANG Scott Drake Radiator Mounting Brackets C7ZZ-8A193-A
1988 FORD BRONCO II Continental Molded Radiator Hoses 61416
Dayco 81321 Flex Hose 1-3/4 X 13 3/4
BLACKHORSE-RACING 3" X 9" Radiator Coolant Overflow Puke Tank Polished Stainless Steel 32OZ
K&S Precision Metals 83063 Round Aluminum Tube, 3/8" OD x 0.049" Wall Thickness x 12" Length, 0.375 in OD, 1 pc, Made in USA

Lastly, I have all these pictures saved.  In the event of another internet picture purge and someone come across this post years from now and wants them I'll send them directly.  Good luck.  


Last edited by TremendousWand (1/01/2021 6:28 PM)


1/02/2021 6:34 PM  #2

Re: 1966 Mustang Coupe 24" Radiator Upgrade

So, you clamped it DOWN from the top but held it to the core support with bolts through the side flanges of the radiator?  I think you will be revisiting that design, hopefully without having to buy a new radiator in the process.  You can simply form a couple of U-shaped brackets with correct padding and weld or bolt them to the car frame below to get the proper mount.  The radiator is designed to have two mounts at the bottom and then the two at the top like you have in order for it to float in the mounts.  When full of water, it weighs a lot.  I am concerned the horizontal bolts you used will not do the job.
Also note the top clamp is designed to use tinnerman nuts like where your front fenders bolt to the inner fenders.  I guess if you have never seen an original one, that might not have been obvious.  Would have saved you some welding.
If using the "stock" lower mounts and upper bracket location, a stock lower hose from a 70 Mustang originally fitted with the 24" radiator fits perfectly.

Sorry to criticize your write-up, but I would hate to see some possible design deficiencies replicated because they "saw it on the FYI forum".  There are lots of different ways to do something, but I do feel the need to speak up when something might have a problem.

Money you enjoy wasting is NOT wasted money... unless your wife finds out.

1/03/2021 7:52 PM  #3

Re: 1966 Mustang Coupe 24" Radiator Upgrade

First off, I got the idea to use standoff mounted to the fender wall from a Mustang 360 article doing a similar mod.  Take that for what it's worth.

Secondly, the tensile strength on a Grade 8, 1/4-20 bolt is about 4000 lbs and 8000 lbs on a Grade 8, 5/16-18.  The top mount is a simple weld modification to the stock bracket so I wouldn't have to change any more parts.  It's the same if not stronger than the original mount.  On the bottom, I'm holding the radiator to the fender wall in compression which goes through 14 gauge 6061 wall.  The weakest point is probably the fender wall it self with whatever thickness steel sheet metal they used and everything else in the car is ultimately mounted to the same sheet metal.  I'm not sure what or how you think this would fail.  It's the same as everything else.  There's a reason scott drake has made a small fortune making reproductions of all these stock brackets, mounts, braces.  It's not as if the stock parts have passed the test of time.

Lastly, the empty radiator weighs maybe 30lbs.  Even with the dual fans and shroud you're talking about an ALUMINUM radiator.  This doesn't weight a lot.  A gallon of water weighs 8lbs so with 4 gallons of fluid in the entire system your might crack 70lbs at most.  The iron engine block alone  weighs 400lbs alone and GT40 cast heads weight over 50 lbs EACH.  Hell I weight 300lbs and drive on 60 year old seats attached to a unibody frame bolted to sheet metal floor pan!  Between that and the paper thin walled reproduction gas tank there is a lot more I'm worried about in terms of safety.

This is the internet and everything comes with the obvious implied disclaimer. I've seen many of mods to where I said to myself there was no way in hell I was doing that to my ride.  I even had a friend of mine try and talk me into installing my T5 transmission by resting it on my chest and bench pressing it into place while he installed the mount.  (He swore he'd seen it done that way)  After 20 years and 100k miles on this could these mounts wear?  Sure, but the radiator is going to wear out and everything else on the car would too including the stock radiator and stock mounts.  This setup is obviously a deviation from stock but there is no obvious deficiency to conclude that it's inferior to the stock setup but everything is a matter of opinion.  I respect yours and appreciate the feedback.

I don't know why the lower hose didn't fit but this is an aftermarket product.  In the grand scheme of things it's a minor issue that could easily be rectified given time, money, and desire.  I'll probably revisit it again when I pull the radiator for a cam swap.

     Thread Starter

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