51 Cambridge build

[Sniper1]

Here we see the poster board being fitted up to test the template. We laid the new radiator atop the poster board to mark out the mounting holes as well as the width, height and shape of the body of the template. We are going to sandwich the mounting plate between the radiator and the radiator yoke, which is why you see mounting studs rather than bolts for the mount.. I do not trust the skinny little nylon mounting things they give you with the fan. They will break and I don't need that.

 

[Sniper1]

Here is the template all marked out. We had to shift the fan to the driver's side some to clear the heater fan motor. I really wanted the fan shifted to the passenger side so as to give more access room for the petcock but that was not to be. I can still get to the petcock but it will be somewhat awkward. I might end up using some tubing/pipe to move it somewhere more convenient.

At this point my pulse rate dropped to the upper 40's and I was pooped out so we called it a day, Covid after effects, got to love it. We did get the template transferred to metal and most of it cut out. I decided that I needed a dimple die to take care of some of the excess sheet metal which I didn't have, so this made a decent stopping point anyway. Still have to cut out the big hole for the fan to blow through. The circle shown is the outer diameter, it's about an inch smaller for the inner diameter of the housing. Which will give me a nice clear area to mount the foam rubber weather stripping to seal the fan to the radiator.

 

[Sniper1]

One last thing we did do, the timing marks on the stock lower pulley, no balancer on this engine, are extremely faint. So I cleaned them up and Marked TDC (small mark) and 5 BTDC (large mark) so I can see them when I am timing the engine. I need to spray it with clear to keep it readable.

 

[MercuryMac]

I sure like those Chrysler honeycomb radiators too, but they are very costly to re-core.
Keep on tinkering.

 

[Sniper1]

Got the cooling fan swap done, sort of.

I am tired of buying third world junk and paying first world prices for it. I had to buy three toggle switches before I got one to work without a failure of some sort. First one mechanically locked up after one use. Second one, the cheap pot metal threaded part stripped upon installation. Going to go to Aircraft Spruce and buy a good one I guess, would have been much cheaper in the long run. Then the temperature sending switch, not sensor, typical GM type aftermarket switch, never worked. Engine got up to 210 then I just grounded out the switch lead and the fan came on. Toggled on the high speed and it worked fine too. If I hadn't of gotten my haircut the other day I would be bald right now, lol. Anyway, the details.

Yesterday I did all the electrical work. Not much to say other than it was a long tedious day of routing wires, cutting to length, crimping, soldering, heat shrinking and wire looming.

Used two relays to control the low and high speed functions of the Derale fan I am running. The instructions for the fan kind of casually mention that the low speed portion needs to be running before you fire up the high speed side. So here's how it's wired, for now.

Low speed relay has switched 12v provided by the wiring harness I put in a while back, this is hooked to one side of the relay COIL. The ground side of the relay COIL is hooked to the aforementioned (failed out of the box) GM temperature switch. If it worked this switch would have grounded the relay coil when the temperature of the coolant hit 185ish. Seems there is some slop in the the actual turn on temp. In my testing I ended up just jumpering the switch wire and the fan came on, I figured if the temperature switch hadn't come on by 210 it was either never coming on or was useless for what I wanted. Once this relay is energized it takes power from the battery side of the remote starter solenoid, thru a fusible link and 10 ga. wire, and sends it to the fan low speed connection. It also sends 12v to one side of the high speed relay COIL connection. This was the easy way to ensure that the high speed side only came on once the low speed side was running. Since the high speed relay will not have power to it's coil till the low speed side was energized it was a fail safe setup.

High speed relay COIL gets it's ground from a toggle switch on the dash, for now. I plan to put a temperature switch on this relay to automate it's activation. But I will probably keep the toggle as an emergency override as well. Output side is similar to the low speed relay, fusible link, 10 ga. wire to relay, outputs to fan high speed connection. It works as expected. Will not turn on if the low speed relay is off, toggle switch cycles it on and off manually.

Near future plans, I have two new Speedmaster switches coming, from Jegs. One is set to turn on at 185, off at 175, this will control the low speed fan. The other is designed to turn on at 200 and off at 185. this will control the high speed fan. In order to install them I have a water outlet spacer with two ports coming as well. Fortunately, the flathead uses the same water outlet setup as the pre 79 Mopars do, so that was easy, lol. Otherwise I would be doing it myself. The low speed temperature switch will work just like I have it wired right now, on the high speed side I will wire the higher rated temperature switch in parallel to the toggle switch so that either can turn on the high speed side.

The relays were mounted so as to not drill new holes in the core support.

 

[Sniper1]

I mounted the fan to the mount we fabbed up. I don't care for the skinny plastic mounting things that are included with the fan. Hence the mount. If you look in the picture you'll see where I used 1/4-20 bolts to mount the fan.

I needed to use some nylon spacers to mount the fan as it bowed up the sheet metal without them. Used some window foam to seal the fan to the sheet metal. Decided not to use the dimple die to make more holes in the mount as I felt that would end up just allowing the air to flow out those holes rather than thru the radiator. If it turns out I have highway speed cooling issues I will revisit this. Here's the mount ready for the fan.

 

[Sniper1]

Installed the fan to the mount, had to use coupling nuts as the hole was too small for a 7/16 socket to fit on a regular 1/4-20 nut It works.

 

[Sniper1]

Here we can see how I secured the long 1/4-20 bolt I used to hold the fan. Bolt head is on the radiator side of the mount (I checked to make sure it clears), a nut secures the bolt to the mount, the nylon spacer is visible and if you have young eyes you might just be able to see the window foam sealing the fan. There is barely a gap to seal.

 

[Sniper1]

Here we have the fan assembly installed, after multiple R&R's to sort out all the details. The three visible mounting studs are actually 1/4-20 bolts screwed in from the front of the core support. The factory just used 4 bolts screwed in from the backside of the core support to hold the radiator in, Not an issue, except the bottom bolt holes in the radiator flange are not slotted to allow you to slip the radiator over them upon installation. Would have been almost impossible to mount the fan and radiator if I kept that arraignment. the unseen one uses the factory setup because the front brake junction block is in the way if I try the stud method. I may relocate that when I redo the brake lines.

In any case, the fan mount will be sandwiched between the core support and the radiator.

 

[Sniper1]

Front side picture of the fan. Had to shift it over to clear the heater blower motor. In the bottom right section of the fan you can see the terminal block I used to connect the fan wiring to my relay setup. Era appropriate setup, lol.

Everything clears with room to spare, though getting to the drain valve is tight, no fitting to attach a hose to drain it either, yes a mess awaits me when I get the new switches.

 

[Sniper1]

Once everything was installed, not going to cover putting in the radiator, lol, it came time to put in coolant. Decided to do it like the factory does, vacuum down the cooling system and let it pull in the coolant. No air to burp if there is no air in the system.

This setup uses shop air and a vacuum venturi to evacuate all the air from the system. Pumped down in the picture. 60 cmhg is about 23.5 inches of mercury.

Got the kit off of Amazon, it was cheap, it did the job.I could spend more and if I had a shop I would of.

 

[Sniper1]

After at least 10 minutes of holding a vacuum this is where i was at. I do have one head bolt that is a tiny bit weepy. 50 cmhg is about 19.5 inches of mercury.

 

[Sniper1]

Some think that the factory put a spring in the lower hose to keep the water pump from sucking it shut, they did not. In the picture below you see why the factory put that spring in there. Maybe the time it takes to uncollapse that hose when vacuum filling the system matters to the factory, to me it did not. I am not rolling a new car off the assembly line every three minutes, lol.

If your lower radiator hose is collapsing at speed, you have a flow restriction somewhere, or a water pump spinning too fast.

 

[Sniper1]

Now for the numbers.

Electrical - on low speed the fan draws 16.5 amps. On high speed the fan draws 22.5 amp, numbers bounced around some so it's a middle number.

Once the engine hit 210 I jumpered out the switch and turned the low speed fan on. Once the low speed fan cooled as much as it could, probably after 10 minutes, I engaged the high speed to see how much farther down it would go.
Ambient was 101 degrees when I measure the numbers with my Ratek IR gun. 185 degree (rated at fully open) thermostat.

Low speed got the temps down to 167, high speed got it to 165 and that I believe is when the thermostat was fully shut.

I did capture airflow numbers. Mechanical was done at idle speed, which is when airflow is at it's least. No shroud in the stock setup, small diameter 4 bladed solid mount fan.

One final set of numbers, it got to 106 yesterday by the time I came in, today it got to 104. I lost 6 lbs, despite trying to stay hydrated. Only 50 more to go, lol.

 

[Sniper1]

I guess I should mention the Derale fan I am running is rated at 1800cfm on low speed and 2400 cfm on high speed. My readings are not cubic feet per minute, but rather feet per second. I figure since the readings are all with the same device and the same spec it ought to be a valid comparison of before and after.

 

[Sniper1]

Well, got the 51 back on the road today, legally that is, lol. Electric fan swap is done, real quiet, barely can hear it at 30 mph with the windows down and you really have to listen for it. Disc brake swap is done, stops nice and straight.

Did a DIY alignment on it, steers straight, handles as well as it ever did, which is not to say it'll be challenging Hyundai's on the road course, lol.

Next up, fixing the oil leak it has had since I first bought it. maybe add a PCV system to it to eliminate that road draft tube.