Looking for a New Radiator for My 1977 K20

[ehjorten]

The radiator in my 1977 K20 350/TH350/NP203 is fairly worn and has some small leaks. I have talked to a local radiator shop that has been in business for over 40 years and they suggested I might want to find a replacement, because they could repair it, but likely the cost would be more.

Anyways, I am not sure where to find the best radiator for a decent price. The one that I have in it, must be the HD one. It is 4-row and measures about 28-1/4" W x 19" H x 2-1/2" D.  I am open to an aluminum radiator, but not one with the plastic tanks, and I want it to mount as stock with the stock rubber supports.

Also...where can it get the proper, new radiator supports? These ones are about 4-1/8" wide!

[MIKE S]

Just my take on the plastic tank radiator. The original type radiators that are soldered seem to always develop leaks. When I used to work on them in the 80s and 90s on my farm I was constantly having them repaired. I have way less trouble on the plastic tank radiators. In the dealership were I work we rarely replace a radiator for a tank problem.My own 2001 Tahoe has 180000 miles on it and just now cracked the tank. If you are concerned about the plastic tanks i would put an all aluminum radiator with high fin count.

[ehjorten]

My experience and experience from guys I know...it seems the plastic tanks always crack way too early and there really is no practical way to repair a glass-filled nylon tank.  Some places can remove the old tank and replace it with a new tank and seal, but this isn't common.  These radiators are really just throw-aways.

I did find this: http://www.usradiator.com/radiators?find=chevrolet-truck-1977-23769&sid=dAyvN6AozW

Not cheap, but might be the ticket.

[bigben5054]

I was in a very similar position as you just a few weeks ago.  I have a 1979 K20 with a 3 core.  Previous owner also ditched the shroud and all the correct mounting hardware.  The radiator was just sitting on the metal support and the guy fabricated some terrible holders just to keep it from falling over.  In searching for a new radiator, I found that most online sources and auto stores carry the same thing - aluminum with plastic side tanks.  In fact, like so many aftermarket parts, I think they all came from the same foreign factory, but are given different names.  Someone pointed me to Champion Radiators, which was looking like a front runner for me until I found a guy (via Facebook marketplace) about 45 minutes from me parting out a 1980 truck.  For $75 I got a radiator, shroud, top plate, all the rubber holders and all the nuts and bolts.

[ehjorten]

Those Champion Radiators are a heck of a lot less than the US Radiators.  They are made in China, so there is the main reason.  I know lots of people want to say screw China over this Coronavirus stuff and buy American, but here is the reality...do you want to pay $600 for a radiator or $200?

[Stewart G Griffin]

Sent PM, might have something you could work with.

[Stewart G Griffin]

ehjorten and others were concerned about the fitment of Champions----and rightly so.....

Inlet side


Pass side


As you can see, they don't quite fit or line up.   Also, at the bottom, the tanks DO  NOT  line up with the pads.   
With mine, it IS tight and snug, so i've relegated it to the weekend project/get to it when there's time projects;  i needed to get the truck running ASAP----THEN i could fine tune it when there was time, i figured.....
It may be difficult to see, but on the passenger/cap side, the pad IS touching the top of the core.  Yes, i know this is not the correct way to do it, but it is secure for now.

My other "complaint" is that, in my opinion, the inlet and outlets are a little too short.   You really have to be careful as far as getting the clamps on there properly.   There is not a lot of room for error.

Those are really minor complaints  in my opinion;  i think it's  a very good product.

[Mr Diesel]

Ehjorton,
I just recently purchased a new radiator the same size as yours. I went with aluminum and plastic tanks. I've had these styles on many of my vehicles for years with no real problems. The factory plastic/aluminum one on my Dodge Cummins lasted 20 years before cracking. In my opinion no radiator can be expected to last longer than that.
I did end up finding an all aluminum afterwards on Ebay for a good price and probably would have bought it otherwise. I'll see if I can find it again.

[VileZambonie]

If you go with that style radiator Stewart, you need to modify the mounting pad insulators.

Aluminum radiators with plastic tanks are more than fine. Make sure you flush the system and maintain it! Use premixed, not tap water mix, ground the core if possible, and enjoy a more modern trouble-free lighter weight radiator that is readily available. If you have a problem with it, you don't need to band-aid it. Most parts stores carry a lifetime warranty on them and have them same day for you.

[ehjorten]

Obviously this is old, but with the pandemic and all, I never replaced my radiator. Recently it has started to leak more and now I am under the gun to get it fixed before Elk hunting. I searched and searched for an all aluminum radiator that would match and the closest was Cold Case, but their radiator has 1-1/2" Inlet and 1-3/4" Outlet. I talked to them and they said they have never seen a 1-1/2" Inlet and Outlet for my application. Well...my radiator is stock and the hoses are correct for my application. 1977 K20 with the HD cooling has a 1-1/2" Outlet. Coincidentally, their LS conversion radiator has 1-1/2" Inlet and Outlet, but both are on the RH side.

Anyways...I pulled the trigger on a Duralast B730 radiator from a local parts store. They had it in stock. I was a little worried about it because this dang thing has a 1-5/16" Inlet, but comes with a rubber sleeve that goes over it to make it 1-1/2". I still am a little leery of a rubber sleeve and then a rubber hose over that, but I guess those sleeves are actually a thing?! With the sleeve the Inlet now measures a few thousands over 1-1/2", but is a sleeve of compressible rubber over hard plastic, while the Outlet measures 10 thousandths over 1-1/2" and is hard plastic. In theory it should work and not leak.

Dimensions of the radiator are really close to the dimensions of the stock copper/brass HD radiator. The core is 2-1/4" thick vs. the stock 2-1/2" and correspondently the overall width of the tank flange is 3-1/4" vs. the stock 3-1/2" width. The overall height of the radiator is 21" vs. the stock 20-1/2", so I am hoping that the radiator is held tight by the rubber radiator saddle mounts. I heard one guy say that he had to cut little pieces of rubber to keep the tank from slopping around, but I think with my new rubber saddle mounts coming it should be held firm.

The core is basically the width of the stock 4-row and they advertise it as a 4-row, but I was actually pleased to find out that it is really a 2-row with with like 1" wide tubes. While I still would rather have a fully welded aluminum radiator I am pretty sure this plastic/aluminum radiator is going to fit the best in my stock saddle mounts without any extra fabrication and it will get the job done. I should have it mounted up this week, so I will update on how it all went, because I do know that several people have asked questions about aftermarket radiators and how they fit to stock.

Stock copper/brass Radiator:
   Core: 28-3/8" Wide x 19" Tall x 2-1/2" Thick
   Overall: ~34-1/2" Wide x 20-1/2" Tall x 3-1/2" Thick to Tank Flanges
   Inlet/Outlet: Inlet (Top Driver's Side) 1-1/2" dia. / Outlet (Bottom Passenger's Side) 1-1/2" dia.

Aftermarket B730 Radiator:
   Core: 28-3/8" Wide x 19" Tall x 2-1/4" Thick
   Overall: ~34" Wide x 21" Tall x 3-1/4" Thick to Tank Flanges
   Inlet/Outlet: Inlet (Top Driver's Side) 1-5/16" dia. / Outlet (Bottom Passenger's Side) 1-1/2" dia. - Comes with a rubber sleeve to make Inlet essentially a 1-1/2" dia.

[VileZambonie]

Hose reducers are common and I actually keep them in stock. Now if your radiator ever has an issue, you can simply swap it out under warranty, keep your receipt in the glove box. If you buy one online and it has an issue, then what do you do? Certain parts are always better to buy local.

[JohnnyPopper]

I just went through that with my K10.

Old copper just gave it up!

The aluminum is exactly as you describe, with the sleeve that I too was wary of, but no problem sealing.

The only glitch was it did not come with saddle mounts, so I had to notch the existing to accommodate the longer square mating surfaces.

Funnier was no one in my area had replacements in stock, not even NAPA, nation wide! (or so she said)

Found Energy Neo's to replace them.

She runs flat out cool, with occasional rises.

One more off my list...

[ehjorten]

So I got my radiator all installed this weekend. All new rubber radiator support pads. The support pads were identical to my original ones, just not worn, old rubber. The width was as expected, for 3-1/2" tank flanges. I had hoped that the new pads would cushion the radiator more so that the slop that I had heard about from searching the internet would not be there; it is. It isn't bad. With all of the hoses and cooler lines hooked up, there isn't much slop. The radiator will be fine for the couple weeks hunting, but after that I will definitely want to correct it and make it right. Other than that, the radiator fits and functions like stock.

I also had bought a new, "clean", stock expansion tank. That appeared to be just like my original, but the mount that bolts to the side of the battery tray was a little too long and, try as I might, I could not get the hole to line-up with the original hole in the battery tray. I just ended up drilling a new hole and installing the bolt where it wanted to line-up.  The "new" expansion tank fill lid fits SUPER tight! I have opened and closed it a few times. It works, but the interference snap fit is a little much.

[ehjorten]

Returned today from the office after my two weeks Elk hunting. The new radiator did perform flawlessly, and despite the radiator tank flanges being 3-1/4" wide and the mounts being 3-1/2" wide, the slight amount of slop didn't become an issue bumping and rattling over 100+ miles of logging roads.

What did become an issue is that my water pump started failing on the drive down to elk camp, despite my getting it all put together an driving it around home for a bit before leaving! My first stop for fuel I noticed a little steam that seemed to be coming from the water pump. It had me a little worried. My second stop for fuel I noticed it dripping from the weep hole and I added a little bit of coolant. My third stop was at an Autozone where I bought a new pump and a couple of gallons of antifreeze. I added nearly a gallon of coolant there as I noticed the temp gauge was starting to be a little erratic.

Then after I arrived at elk camp, I got ready to go out to do a little evening scout two days before the opener. Driving out of our camp area, one of my V-band collector clamps decided to pop the clamping bolt and the exhaust got really loud! Parked my truck and went hiking! Didn't see anything, and I hiked about 3/4 of a mile up from camp to get cell reception to inform my loved ones that I had made it and everything was alright.

A buddy stopped off at a local truck shop and picked up 3 different V-band clamps on his way in, and I fixed that the next day. It wasn't until midday on about the 5th day of elk hunting that I started disassembling the front of the engine to replace the water pump. Got it all replaced in a couple of hours and filled back up with coolant! Fun adventures in elk camp!

Good thing I had a tarp and brought an old throw away pop-up tent because they were very, very handy for laying under the truck and working in the engine bay when it was pouring down rain!

End of the story is that my truck made it home under it's own power and everything is good. Elk hunting wasn't as good, as we came away with only 1 elk out of 3-1/2 people. I say 3-1/2 people because one of my hunting buddies had to leave four days into hunting to go to Alaska to catch halibut. He flew up for a 48 hour weather window and then the weather changed as it does in November in Alaska, and he sat there for a whole week waiting for the weather to change! Lost out on his whole elk hunt.

[philo_beddoe]

If you go with that style radiator Stewart, you need to modify the mounting pad insulators.

Aluminum radiators with plastic tanks are more than fine. Make sure you flush the system and maintain it! Use premixed, not tap water mix, ground the core if possible, and enjoy a more modern trouble-free lighter weight radiator that is readily available. If you have a problem with it, you don't need to band-aid it. Most parts stores carry a lifetime warranty on them and have them same day for you.

I always wondered why you installed that style in mine. I’ve always been partial to the original heavy copper/brass which are like almost $700