'76 K10 400 Small Block Fan Shroud

[CmdrShepard]

Forgive me if this is in the wrong location, but I didn't see a 'better' place to post this.

I'm currently working on resurrecting my '76 K10 from the dead after it sat for more than a decade. I've managed to get it running (but not driving) and had some issues with overheating already. The fan shroud is completely missing and I'm unsure of exactly which style I need to replace it. So far looking at LMC and most of the other classic truck parts sites, along with googling different forums like this for info, everyone only mentions shrouds for the 305/350 and the 454.

Does anyone know exactly what type of shroud I need, a part number, or any other lead? This is a 1976 K10, small block 400, auto (TH350), with no A/C. If my understanding is correct there were two different cooling options (HD and non-HD) and I'm inclined to believe it is the HD option. From my research it seems the top of the non-HD radiator is well below the top of the core support and I believe mine is almost flush with the top of the core. The truck is not with me at the moment but I can go double check this tomorrow.

Thanks in advance!

 

[Dave M]

G'day and welcome aboard. Best bet would be to post some pic's of what you actually have. From there, you will have someone better advise you of which way to go. A lot of good help, and a lot of good people here on this site. Good luck with your project.

Forgive me if this is in the wrong location, but I didn't see a 'better' place to post this.

 

[Rusty Nail]

Uhh.....

I know somewhere is 76 that stuff changed or got different with the grilles.
I'll attach a pictures of my 77C20.
It is FOR. SURE. HD cooling optioned and this IS the correct 1977 (only) should and radiator support..

Good luck finding one if it's what you need. yeah..it's one piece. Look at it. Omg!

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Really happy to find one.
Those parts in my truck are right as rain HD cooling for 77 small block. Bank on it.

I dont believe for one second that simply being factory optioned a 400 qualifies for default HD cooling. Chevrolet wasnt selling new trucks with warranties that overheated. Much 400 folklore is jive spread by people that dont know and dont have one. Don't believe the hype

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BUT you CAN believe the hype about hard to find fan shrouds and radiator mounts. THAT. ****. IS REAL.

It started changing in 76 maybe even late 75s i think. The fan shrouds. You might could find one in a 76 but real HD 77s for sure was the end of those. Pretty sure that didnt carry to 78 because emissions and the frame. The core support maymy truck maybe?
Look I got no definitive source... I'm just some dude on the internet.
But especially without AC? I think that would move you even further away from Heavy Duty cooling and I'm not convinced that is the right tree to be barking at.

Hay but im no old truck encyclopedia either. I thought I learned some things fixing my 77 and I guarantee it now is OE as it can be. That correct radiator is very expensive! -$250? A lot!

Again, good luck. Pro tip? = Check your motor mounts.

Lemme know if I can help otherwise - I have another radiator mount like pictured.

 

[Dave M]

Wow, there's a hell of a difference between that and my '76 BB, A/C, 4 row radiator !

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[gotyourgoat]

The fan shroud didn't have too many options throughout the years. 6cyl had different ones for sure and the HD option.
However if you are having overheating issues and the truck is stationary you have other issues to address well before finding a fan shroud. Have you broken your thermostat housing bolts off in the intake yet?

 

[Rusty Nail]

haha!
Yeah thermostats are good if they open and close.

We ere studyin about fix or flee in a different thread tho cmndr. How many hours of labor is repairing a pre-former intake worth?

That's funny.

Tell us about the "sentimental value".

Those are my favorite ones.



Got any pix?

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[gotyourgoat]

haha!

We ere studyin about fix or flee in a different thread. How many hours of labor is repairing a pre-former intake worth?

That's funny.

Tell us about the "sentimental value".





Got any pix?

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To add insult to injury, it's not even a performer. Even more mismatched than that. And I would of thrown it into the ravine on the side of the house to hopefully break the legs of varmit deer that keep jumping the fence and eating my garden if I had to pull it.
Sentimental value for the previous previous owner's choices...0.0 Most of Mr surly came out btw...https://www.gmsquarebody.com/threads/broken-bolt-square-paperweight.30618/page-2#post-607502


Fix that overheating issue before even thinking about a shroud. We don't want to be blamed for the wrong shroud when your **** was destined to boil over and melt already.

 

[Rusty Nail]

Yeah!

And then you smash it up with bad motor mounts and your time, money, and work gets chopped to bits in seconds when we can't even get a lousy picture of your so-called "400".
We'd hate for that to happen.

Turn the phone and take the picks already!

Might have to cutcha off...

 

[CmdrShepard]

Well I'm back with some pictures and I'm glad I took them because my memory let me down on the size of the radiator. It's 28"x19" and I believe a 4 core. The fan was off while I was trying to get the motor unstuck from a bit of rust buildup after sitting so long. This may have been why it overheated, but I only had it idling for about 10 minutes before she started steaming. Currently the temp gauge is not working so while running it for a few minutes today (with the fan) I wasn't sure if it was getting too hot or not. I've traced the gauge issue down to a bad temp sensor (is 20 megaohm out of spec? ), which I'll hopefully have replaced tomorrow. I suspect the thermostat is working, or isn't stuck closed at least, because the hoses all heated up evenly.

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Some other info: It is in fact a 400, but it is not a factory 400. The VIN code is L which indicates it was a 350 4bbl. However, the block casting number comes back to a 71-72 4 bolt main or a 74-80 2 bolt main small block 400. I suspect it's the later 2-bolt since it also has the "400" badged grille. I'm thinking the previous owner bought a parts truck and swapped the motor and grille in place (among other fabri-cobbled shenanigans, some visible in the above images) sometime in the '90s when these trucks were more plentiful.

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Here's a picture of the truck. She's not much to look at right now, especially with the skinny roller tires on a lifted truck with cut fenders and busted fender flares. My main concern at the moment is getting it moved out of its hole so I can have it towed to my house and start going to town on it over the winter.

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Anyways... Do you all think a shroud from a '76 350 would be the correct choice?

 

[Rusty Nail]

Dude you have a 509. That is the good 400 hi nickel.
Worth good money if you wanna sell it before you break it..just sayin. Matter of fact , you could probably sell it to me lol.

The blue paint on that block is correct.

In my experience a two piece should will not work. Way different size than you want. Reckon you'll need the one piece as shown looking at your radiator support to be correct.
Somebody else may be able to tell you about how to install or hack in something different but I'm no help in that department.
What you want is Not sold in the aftermarket, I can save you the trouble of looking.
I sure as hell buy A one piece shroud if I found one in a 76.
Best bet is to find one in a '77 I think. I'm tellin ya everything I know about it.
Took me four months of lookin, you've got plenty of time!

Good luck!

P.S. great pix. Rad truk.

If it run that hot that fast .... There's no water in the oil , right? It's got good oil in it? One of oil's jobs is to help cool. ...Might need head gaskets. Prolly a really good idea to take the thermostat out while you work on it. Id also want to see under the valve covers. Lookin for traces of coolant.

400 Siamese bore gaskets fail between 3 and 5 or 4 and 6. Worth a shot to pull those four plugs and see what you can see. Water might come out or the plugs may be wet. How does it run? Any smoke?

 

[Salty Crusty]

^ 509 is PROBABLY 2-bolt mains. The -511 is the early one that was only available with 4-bolt mains. I have a couple of '509's in my shop, both '75. Word is they got lighter in '76 or '77 with material removed from the mains.

OP: You may or may not have any air going through your radiator now. I'd get the shroud - or at least something resembling one - now. Your fan is pulling ambient air from all around it and not through the radiator. Air is like everything else, it takes the path of least resistance. Where do you think it's going to go?

How do you expect it to cool with no air moving through the radiator? I can guarantee any engine in any old vehicle I own will overheat if I pull the shroud off.

 

[Termite_Delight]

^ 509 is PROBABLY 2-bolt mains. The -511 is the early one that was only available with 4-bolt mains. I have a couple of '509's in my shop, both '75. Word is they got lighter in '76 or '77 with material removed from the mains.

OP: You may or may not have any air going through your radiator now. I'd get the shroud - or at least something resembling one - now. Your fan is pulling ambient air from all around it and not through the radiator. Air is like everything else, it takes the path of least resistance. Where do you think it's going to go?

How do you expect it to cool with no air moving through the radiator? I can guarantee any engine in any old vehicle I own will overheat if I pull the shroud off.

I have been running my '76 (350ci) with no shroud for a month now, never overheats. I think you have other problems.
Did you flush the rad and block?

 

[AuroraGirl]

I have been running my '76 (350ci) with no shroud for a month now, never overheats. I think you have other problems.
Did you flush the rad and block?

my 77 ford ltd with 400 would overheat idling or in traffic but cool on freeway. the fan doesnt move enough air without a shroud because its so close to the radiator and it just pulls air around it rather than through. If you push air with a pusher, you wouldnt have as much issue with this.

edit:

old, tired, clogged, contaminated cooling systems need all the help they get

 

[75gmck25]

This is a picture of my '75 350 K25 with HD cooling. Its a 3 row radiator, 17" core, with stock one piece shroud and metal fan.

Since this picture I've swapped to a JEGS Champion CU161 3 row aluminum radiator. I'm using a Stewart Sage One high flow water pump, high flow 195 degree thermostat, and a Hayden Severe duty fan clutch. My engine runs very consistently at about 185 degrees, and only gets up to about 195-200 if I have in it hot weather, idling with the A/C running.

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Bruce

 

[Rusty Nail]

^ 509 is PROBABLY 2-bolt mains. The -511 is the early one that was only available with 4-bolt mains.

That's right , I went an looked. 511 is the 4 bolt block, my bad. 509 is the good 2 bolt though.