Sbc to bbc fan shroud issues

justinbrugg · Wednesday at 10:49 AM

Hello everyone, I just recently installed my rebuilt 454 in my 2wd 78 c10 and I’m having issues with fan shrouds. I had a sbc shroud I thought could work but it very much doesn’t and take up too much space. I had gotten a bbc shroud and have been messing with it for hours yesterday not able to get it fit in quite right; it doesn’t sit at the bottom nicely and I can’t find a good way to mount it at the top. I have both the wide metal top mount for the rad and shroud and the smaller 2 arms that do the same. What would really help is if anyone had photos of there fan shroud set up the a BBC specifically how it sits at the bottom. I’m also interested if anyone just went with electric fans. It’s a pretty solid motor and it definitely needs a shroud. If it helps I have a 4 core oem replacement radiator.

Thank you for the help

82sbshortbed · Wednesday at 10:54 AM

I ran into the same issue with my BBC swap. I ended up leaving it off. It sits in the shed now because I got tired of messing with it.

Sad Sack · Wednesday at 11:50 AM

Just curious but how many cores was the original rad?

nvrenuf · Wednesday at 12:51 PM

It's been a while since I had my '80 but I didn't have any problem installing an HD 4 row radiator with shroud in it after swapping to a 454. I used all big block parts (flat top plate, top/bottom rubber mounts and shroud) on my original small block 3 row radiator core support. I picked an application with HD cooling and bought everything for that (iirc, '80 K30 w/ 454 and heavy duty cooling option).

- Are all of your parts for 73-80?
- Seems like there might have been tall vs short radiators (about 3" difference), are all of your parts matched similarly?
- Is the radiator a factory type unit or an aftermarket unit that you had to modify parts to fit?

Edelbrock · Wednesday at 1:22 PM

OEM Cooling systems seem to be designed to run right on the edge of overheating. The thermostat opens all the way, and then what ever happens happens. Go up hill, haul a load, turn on the A/C and the engine overheats? That seems lame.

I had shroud problems on my rig. I wound up getting a clutch fan with more blades, and then used a spacer to get it much closer to the radiator. Then I closed off the space between the core support and the frame using a sheet of thick plastic because a LOT of air was being drawn through this area by the fan, which would be bypassing the radiator. After that I put a chrome 3/4 shroud on there (mounts easily to any radiator with plastic "zip tie" like things), but I mounted it very close to the fan (its flexible, so you can change the diameter). The closer the better, as long as it doesn't hit the fan when the engine flexes its muscles.

So the only area of the fan that is not shrouded is about 5 inches or so on the bottom left and bottom right. I have some chrome material to finish wrapping the shroud around all the way to fill that 5" gap, but I decided not to, because of the lack of need. With this setup, my thermostat is regulating the temperature more than anything else. Cooling system is efficient enough that the fan clutch never comes close to fully engaging, and the engine temp never rises at all above where the thermostat will allow it to even when its 90 degrees out, and I'm pushing the motor hard.

Using a thermal temp gun helped a lot, to see what difference the changes made.

So ya, I recommend just building your own setup.

Thermal gun: $14
Spacer: $12
Chrome Shroud $39
Fan (junk yard) $15

(Google pics)

justinbrugg · Wednesday at 4:52 PM

Sad Sack said:
Just curious but how many cores was the original rad?

2 core I believe.

justinbrugg · Wednesday at 4:53 PM

82sbshortbed said:
I ran into the same issue with my BBC swap. I ended up leaving it off. It sits in the shed now because I got tired of messing with it.

Are you running a fan? How is your big block set up?

justinbrugg · Wednesday at 4:58 PM

Edelbrock said:
OEM Cooling systems seem to be designed to run right on the edge of overheating. The thermostat opens all the way, and then what ever happens happens. Go up hill, haul a load, turn on the A/C and the engine overheats? That seems lame.

I had shroud problems on my rig. I wound up getting a clutch fan with more blades, and then used a spacer to get it much closer to the radiator. Then I closed off the space between the core support and the frame using a sheet of thick plastic because a LOT of air was being drawn through this area by the fan, which would be bypassing the radiator. After that I put a chrome 3/4 shroud on there (mounts easily to any radiator with plastic "zip tie" like things), but I mounted it very close to the fan (its flexible, so you can change the diameter). The closer the better, as long as it doesn't hit the fan when the engine flexes its muscles.

So the only area of the fan that is not shrouded is about 5 inches or so on the bottom left and bottom right. I have some chrome material to finish wrapping the shroud around all the way to fill that 5" gap, but I decided not to, because of the lack of need. With this setup, my thermostat is regulating the temperature more than anything else. Cooling system is efficient enough that the fan clutch never comes close to fully engaging, and the engine temp never rises at all above where the thermostat will allow it to even when its 90 degrees out, and I'm pushing the motor hard.

Using a thermal temp gun helped a lot, to see what difference the changes made.

So ya, I recommend just building your own setup.

Thermal gun: $14
Spacer: $12
Chrome Shroud $39
Fan (junk yard) $15

(Google pics)

ill order one of those shrouds. I saw them but I didn’t know if they’d be one of those universal crappers that don’t really work or fit in anything. Thank you!

xm20k · Wednesday at 8:10 PM

I don't even run a shroud due to all the garbage sold that claims to fit but doesn't. A good pump, fixed blade fan, aluminum rad, 160 thermostat and spaced to be closer to rad than engine. She runs in the 170–175-degree range, then again she's not a winter ride so no heater. But I have been daily driving it to work to get some milage on it before I flog it at the track. These things are just big bricks, so I think just driving probably forces more air thru than people realize.

You must be registered for see images attach

This engine is 11.25 : 1 with a 252 (actual duration) and .600 lift roller cam

Edelbrock · Wednesday at 8:39 PM

xm20k said:
I don't even run a shroud due to all the garbage sold that claims to fit but doesn't. A good pump, fixed blade fan, aluminum rad, 160 thermostat and spaced to be closer to rad than engine. She runs in the 170–175-degree range, then again she's not a winter ride so no heater. But I have been daily driving it to work to get some milage on it before I flog it at the track. These things are just big bricks, so I think just driving probably forces more air thru than people realize.

You must be registered for see images attach

This engine is 11.25 : 1 with a 252 (actual duration) and .600 lift roller cam

Sweet ride man.

I was going to make a recommendation on what I might do differently, but it doesn't look you need any help. That motor looks totally awesome.

I don't see tunnel rams that often anymore. If you could find a ... (biting my tongue).

Cool rig man, you should upload more pics.

82sbshortbed · Wednesday at 10:45 PM

justinbrugg said:
Are you running a fan? How is your big block set up?

Yes but no shroud on it.

bucket · 2025-06-14T08:30:38-0400

justinbrugg said:
Hello everyone, I just recently installed my rebuilt 454 in my 2wd 78 c10 and I’m having issues with fan shrouds. I had a sbc shroud I thought could work but it very much doesn’t and take up too much space. I had gotten a bbc shroud and have been messing with it for hours yesterday not able to get it fit in quite right; it doesn’t sit at the bottom nicely and I can’t find a good way to mount it at the top. I have both the wide metal top mount for the rad and shroud and the smaller 2 arms that do the same. What would really help is if anyone had photos of there fan shroud set up the a BBC specifically how it sits at the bottom. I’m also interested if anyone just went with electric fans. It’s a pretty solid motor and it definitely needs a shroud. If it helps I have a 4 core oem replacement radiator.

Thank you for the help

Do you have the short or the tall version of the radiator? The tall one is roughly the same height as the core support, while the short version is several inches shorter than the core support.

Turbo4whl · 2025-06-14T17:24:52-0400

On my 1982 small block to big block swap, I used a 6 cyl radiator top mount. More of a guard than a shroud, it holds the radiator fine. Added a small metal L bracket to match the hole spacing. The fan, 7 blade clutch fan, from the sedan the rat motor came out of. No over heat problems

You must be registered for see images attach

Ricko1966 · 2025-06-14T23:05:11-0400

justinbrugg said:
Hello everyone, I just recently installed my rebuilt 454 in my 2wd 78 c10 and I’m having issues with fan shrouds. I had a sbc shroud I thought could work but it very much doesn’t and take up too much space. I had gotten a bbc shroud and have been messing with it for hours yesterday not able to get it fit in quite right; it doesn’t sit at the bottom nicely and I can’t find a good way to mount it at the top. I have both the wide metal top mount for the rad and shroud and the smaller 2 arms that do the same. What would really help is if anyone had photos of there fan shroud set up the a BBC specifically how it sits at the bottom. I’m also interested if anyone just went with electric fans. It’s a pretty solid motor and it definitely needs a shroud. If it helps I have a 4 core oem replacement radiator.

Thank you for the help

Read this,then use stock pieces,modified stock pieces,homemade or what ever you have to do. But now you'll have the knowledge of how and why a shroud works and how to set it up best.And I would advise against using electric fans on your set up.

PRI Tech

Proper placement of an engine-driven cooling fan on a race car is crucial for maximum cooling efficiency and avoiding cooling problems.

www.performanceracing.com

Sbc to bbc fan shroud issues

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