Is there a difference between a SB and BB shroud? If so what are they?

I tries a SB fan shroud on my BB. It rubbed at the alternator and on the lower pulley. The SB shroud is too deep, sticks out too far from the radiator. Also my fan would hit the inside top of the shroud when I would get on it. Wore a hole in the top of it. Put I BB shroud in for cheap from Original Parts Group and took care of the problem. Also cools a little better since the fan is placed at the proper spot in the shroud.

What Jason said. My 402 runs much cooler in traffic with a BB shroud than it did with a SB one. With the SB one, the fan blades were all the way inside the shroud instead of half in/half out like they should be. The issue can also occur with short vs long water pumps or removing a fan clutch without using a spacer to make up the difference.

I'm trying to market an aluminum shroud for 68-72 Chevelles/ El Caminos and wasn't sure if it work on a S.B.
Dimensions are 32"X20"X 9 5/8". I guess it will be just a bit short for the S.B. Please check it out on www.steelpackgarage.com

I have a SB shroud in my 69 with a BBC....and I attribute this to how good my car cools with a measy 2 core rad. and 550hp. It is close to the alt. and crank pulley, but they dont touch. The SB shroud is deeper, and in turn the fan is covered more, making teh air HAVE to come through the raditiar. The BB shrouds leaves the fan a little exposed. Will now have a 625-650hp motor, lets see how the 2 core rad and sb shroud hold up.

http://i134.photobucket.com/albums/q116/VGIORDANO_2007/HPIM0064.jpg?t=1238842393

You also have a 71-72 shroud installed in a 69 which uses a larger fan (19") than what a 69-70 uses (17"). If it were a correct style 69-70 SB shroud, it wouldn't work. I have one of each in my garage. I'll take pics and post them up.

Thanks guys, your imput is important to me. 69-CHVL great shot thanx ...how the heck do you post a picture on this thing?!?!?! I'd like to show you what I'm talking about.

Hi Vince,just wondering if your aware the fan shroud your running is not from a 69 chevelle?

Anyway,that's why you get such good cooling results from a stock gm 2 core with your hot bbc because that non stock shroud covers the full Rad for considerably better /more efficient cooling as compaired to the stock bbc shroud that doesnt cover the full rad in 69 & 70 chevelle's.

The stock 69 chevelle bbc shroud doesnt cover the last 25% of the radiator from top to bottom on the drivers side so the fan cant pull air thru it for more cooling when in traffic or at an idle. Thats a significant reduction in cooling IMHO,dont know why gm did that for 69 & 70 only in the chevelles ?

I believe the shroud your running is maybe from a full size chevy like Impalla or Monte for 1971 . But i think the chevelle's from 71 on up also got that bigger shroud your running in your 69 . That shroud is a far better design for approx 25% increase cooling in traffic & @ an idle simply because it covers the last 25% of the radiator for full coverage so the fan can pull cool air thru 100% of the radiator and not only 75% with stock shroud for 69 bbc.

Scott

Scott, yeah I know its not the right one, as Tom also pointed out. It was on the car when I got it, and I thought it was the right one for a while b/c it actually fit perfect! Joe cam over one day and told me it wasn't correct. But your right, it really covers the entire radiator, and the fan is buried way deep. So maybe that the secret...using an incorrect shroud lol!

We'll see how it goes with the new 600+hp motor, if it runs too warm, I'll try an alum rad out.

Yeh Vince,you sure got it right on your car with that fan shroud that covers the radiator completely cooling your stout bbc fine with just a std run ofthe mill GM 2 core rad shows that 'sthe case,GM missed the boat on that one for sure in 69 & 70 but FINALLY got it figured out in 1971.

If my car wasn't completely #'s matching that i have owned for over 30yrs ithat want to look right i would definately run the fan shroud you run.

And BTW,next time your under the hood could you please take a close look at your shroud to see if there's a gm PT# on it & if so please report it back to me/us here?

Also,are you also running a 772 7 blade clutch fan and hd/ac type fan clutch?

If your's is not the 772 fan can you get the pt# off the fan too that should be stamped on 1 of the blades oand if not that measure the overall diameter?

Are you running a std rep water pump wth a stamed steel impeller or an aftermarker hi flow w-pump with a hi efficiency cast iron impeller or a stamped steel impeller with the dist pop rivited to the back of it to reduce cavitation & increase pumping pressure?

I ask that because i would like to know exactly which shroud your running in case i get a problem with a bbc running hot in traffic in a 69-70 and if the person i am working on the car for doesnt mind running that better full coverage shroud like you have i could try to find the same exact shroud to help cure any heating up in traffic woes.

Sorry for all the questions but your setup flat out works great and i would like to document the shroud and fan setup so we can offer it up for a really good street cooling setup for 68-72 bbc chevelles tha will cool fairly hot setups too .

Man,could you imagine how well it would work going from your current gm 2 core to one of the newer style HI EFFICIENCY 3 CORE radiators they offer these days?

An alumitech would be awsome with your setup,it could likely sit all day in 90-95 deg heat in traffic and not get over 180-185 deg F.

Thanks...scott

I got hung up in traffic for a while once in 90*+ heat, started to creep up around 200, but that was an unusual circumstance, was sitting still for like 20 minutes. Otherwise, she runs 180* all day long. I am running an Edelbrock pump and HiPo T-stat, although I cant say that much difference when I installed them.

Fan shroud part# - Guide 3986906. Little bit of trimming was done...very little in the upper corners.

Fan - couldnt find any #'s, but has a 7 blades and a dia. of about 18"

Fan clutch, couldnt find any #'s, maybe somebody can tell me what it is so I can replace it with the same when the time comes:

http://i134.photobucket.com/albums/q116/VGIORDANO_2007/IMG_1015.jpg?t=1239017564

http://i134.photobucket.com/albums/q116/VGIORDANO_2007/IMG_1016.jpg?t=1239017828

Vince,thanks for the info

Scott

I didn't forget to get the fan shroud pics, just have been busy and feeling kinda under the weather to get the 70 out of the trailer so I can get pics of the shroud on it. Give me a couple more days and I'll have them for ya. I also have a 71-72 BB shroud in my shed I need to dig out for comparison.

Vince,thanks for the info

Scott


Scott, can you ID the fan and clutch for me, or anybody else?

Tom,thanks for the update and no rush but that info you will have will be much appreciated when you get a chance to post it.

Thanks...Scott
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Vince,your fan clutch looks to be an older original until thats a thermostatic type but if it's still working ok i would reuse it.

If reusing it i would take a couple mins to remove the rust/corrosion from the thermostatic spring on the front of the fan clutch that faces the radiator so it will conduct the heat faster/better for faster/better clutch operation.

But if your going to replace it let me know and i will send you the napa pt# for a hd fan clutch that should fit your fan (with long water setup) that looks to be the same design as the older gm 772 fan . But your fan is a later/newer issue of the older 772 fan but as you noted the newer fan has no pt#.

Scott