Stock or electric fan

[Mr. Machanic]

I'm working on ordering parts for replacement.
First on the "mechanical" list is the radiator.
The original does not leak; however, there is some vane corrosion and detatchment, so it won't be long and I wish to not get stranded.
So, I've been looking at replacements for the 28x19x2.5 size.
I don't care for the plastic cheeks and the aluminums look to be around 3 to 4 bills....it is what it is.
My fan is a non-clutch 18" but the shroud opening is just over 20".
My first guess is the original 19" fan has been replaced with this 18" because the clutch failed.
I have thought about a flex fan. Are they a good replacement or keep looking?
My other consideration is for an electric fan set up. Most likely 2 fans.
Anybody have feedback on the electric conversion?
I know a couple hp will be gained and that's a plus.
Thanks for your input.

[JohnnyPopper]

I did the same on my '78 K10, aluminum radiator runs steady, needle hardly ever moves.

Electric fan for sure, did pick up HP, so much peppier that my wife noticed...

Mine had a flex when I bought it, very noisy, ditched it first thing.

[Mr. Machanic]

Thank you JP.
I appreciate it.

[Mr. Machanic]

Update:
It was a beautiful day (ok....not actively down pouring or a blizzard) here in ohio.
Summit Racing is not far so I took Big'in out for a run.
I didn't find one in the "demo" isle so I went to the order desk and looked over the options and got an all aluminum one for less than the factory replica.
Made it home in one piece and started to dismantle. The tranny lines were stubborn, but got them out with very minimal "nut boogering" on the top one and none on the bottom one. Also pulled the overflow tank out.
BTW...What's the deal with 10mm bolts holding on the tank and fan shroud? About drove me up a tree trying to find a socket. Sheesh!
Anywho, got everything out and the new one in...mostly. I had to cut some 3/8" sheet rubber to make saddles for the new radiator. That took a few extra minutes, but soon it was in.
The new one is about an inch short on the 28" length.
But the old rad was not a 2" core like specs call for, it is 1" ,so this ain't the original. Maybe a second or 3rd replacement.
Well, the "inch short" in length sure did throw a monkey wrench in the works.
The original shroud is not going to fit back on because there's shroud where inlet hose needs to be. Hacking the shroud will look like a hacked shroud and I'm trying to not make it look like some knuckle head got in there.
So back to Summit to do a premature electric fan upgrade.
Now, this just got about twice as expensive as I had planned.
Aluminum shroud, 2 fans and the wiring harness later and I really need to get out of there.

On the agenda for tomorrow:
Find a better paying job....
Hit the hardware store for bolts to mount the fans. Them little zippy ties going between radiator fins is kinda lame. (In my book)...
Drill some holes in the shroud for fan bolts.
Mount shroud to radiator and fans to shroud.
Throw it back in. Wire it up.
Then read instructions. Rinse and repeat.

Does anybody actually run those zippy ties thru the fins?
I mean my first thought was, those fans are kinda heavy and you are asking little aluminum fins to hold that weight with heat and vibration?
I'll stick with brass bolts and a touch of thread locker, thank you.

[Captkaos]

Hard to follow this but if you bought a replacement radiator and it isn't the same size, you bought the wrong one...
I have had good luck which Spectre, Cold Case and Summit branded, fit like factory.

[Mr Diesel]

Don't use the zip ties through the radiator. Years ago a radiator shop warned me not to do that. I did it anyway and sure enough, a year or two later I had leaks there in the new radiator.

[ehjorten]

Hard to follow this but if you bought a replacement radiator and it isn't the same size, you bought the wrong one...
I have had good luck which Spectre, Cold Case and Summit branded, fit like factory.

Not completely true Capt'. I bought a "replacement" radiator for my '77 K20 with HD cooling. It was one of those aluminum cores with the crimped on plastic tanks. I really wanted a custom, all-aluminum one, but the cost wasn't in the cards. It was almost a perfect fit, except the stock copper/brass one had tank flanges that were 3-1/2" wide and the replacement one had tank flanges that were 3-1/4" wide. The radiator, even with new rubber isolators is a little loose in the supports. So far it has been okay, but I am thinking about casting new rubber isolators that fit tighter to the tank.

[Captkaos]

This is what I was referencing

The new one is about an inch short on the 28" length.
But the old rad was not a 2" core like specs call for, it is 1" ,so this ain't the original. Maybe a second or 3rd replacement.
Well, the "inch short" in length sure did throw a monkey wrench in the works.
The original shroud is not going to fit back on because there's shroud where inlet hose needs to be. 

1/8-1/4 diff is one thing, but a 1" difference of width where the shroud won't work is a different story.  (The 1" core vs 2" core is generally not relevant as they used the same tanks on many of the trucks, the cores had more rows/thicker.

I have also had issues with the plastic tanked versions being loose.  Most of it is from the deterioration of the original isolators and the difference in the flange dimensions.  Casting new ones would definitely benefit and they are much different than the original flanges.
I am currently replacing the plastic tank version in my 87 R10 Twin turbo truck with an all aluminum version.  Wont buy another one of those...  ehjorten Who's did you buy?

And agree, never run the zips unless you just like buying radiators.

[Mr. Machanic]

The inch difference was in the 28 inch dimension.
That was 1 inch short.
All other numbers were good.
The specs called for a 2" thick core and the one I removed was only 1 inch.

Sorry, for the "hard to follow" explaination.
It can be a challenge to convey something for others to understand.
Heck, it's hard enuf to do it over the phone, sometimes.

I'll try to do better....lol....

[Mr. Machanic]

A little help from the collective..Please.

I need to find a 12v sourse that turns on and off with the key.
I'm looking thru my manuals but can't seem to find a good schematic.

Here us a pic of my firewall block and I would like to pick it up on the engine bay side of the block if possible.

[ehjorten]

This is what I was referencing

The new one is about an inch short on the 28" length.
But the old rad was not a 2" core like specs call for, it is 1" ,so this ain't the original. Maybe a second or 3rd replacement.
Well, the "inch short" in length sure did throw a monkey wrench in the works.
The original shroud is not going to fit back on because there's shroud where inlet hose needs to be. 

1/8-1/4 diff is one thing, but a 1" difference of width where the shroud won't work is a different story.  (The 1" core vs 2" core is generally not relevant as they used the same tanks on many of the trucks, the cores had more rows/thicker.

I have also had issues with the plastic tanked versions being loose.  Most of it is from the deterioration of the original isolators and the difference in the flange dimensions.  Casting new ones would definitely benefit and they are much different than the original flanges.
I am currently replacing the plastic tank version in my 87 R10 Twin turbo truck with an all aluminum version.  Wont buy another one of those...  ehjorten Who's did you buy?

And agree, never run the zips unless you just like buying radiators.

Capt'n it was the Duralast B730 HD Cooling radiator. It was identical to the original Copper/Brass HD radiator in fit form and function, except for that 1/4" width of the tank issue. Usually with most aftermarket all aluminum radiators the tanks are not rounded at the tank flange like the stock ones. That makes it sit funny in the isolators. There are better, high-end ones out there that are radiused in the corners.

[Mr Diesel]

A little help from the collective..Please.

I need to find a 12v sourse that turns on and off with the key.
I'm looking thru my manuals but can't seem to find a good schematic.

Here us a pic of my firewall block and I would like to pick it up on the engine bay side of the block if possible.

Use a test light and determine which of your alternator terminals is hot when engine is RUNNING. You won't want to power fans directly off that terminal but it will run a relay easy. Bonus is that fans or whatever you have will always shut off when the engine is turned off but you can leave key on for radio or whatever.

This won't work if you have an alternator converted to "one wire" charging, which unfortunately is very popular with aftermarket rebuilds. Those all seem to be hot on all terminals at all times due to the "one wire" regulator use.

[VileZambonie]

Any time you want the big dog, order the big block radiator, mounts and insulators. The aluminum/plastic units are fine and drop right in. I just did one on a K20 today. e-Fan should have a thermostatic control relay with a manual override.

[Mr. Machanic]

Well, that was special.
I certainly don't shine at automotive wiring, yet.
So, I probed 3 wires in the loom coming from the direction of the alternator, whis is not a 1 wire. It has 3.
Anywho, none of the wires, which looked to be called out on the Chilton schematic, had 12V with engine running. I decided to take a look at the fuse block under the dash. I found one labeled "batt"...well heck that should work. I ran a wire in along the speedo cable and plugged it in. The low speed fan came on. I had the temp pot turned all the way down.
Now I know everything is wired correctly. Looked around some more and found a pigtail with "acc" labeled on it. Plugged into that and turned on the acc...fan runs.
Then I started the engine and set the temp to around 170 for the first fan and 180 for the second. This 12v source was needed just as a signal to tell the system it can run if need be.
I don't have a tach, but I did notice a tad higher idle. Stock fan had no clutch.
All in all, I'm happy with the Summit label radiator, shroud and 2 fan kit. The twin relay controller was extra and I set it up for 1 low speed fan and 1 high speed fan. And the arrangement is low fan closest to return.
I have wire loom around here somewhere...all those wires hanging out there bothers me. But that will be a project for another day.

[VileZambonie]

The high current side of the relay(s) should be fused, getting its power directly from the junction block or battery post and not from the fuse box. Tapping into the fuse box to activate the control side of the relay(s) is fine.