Author Topic: Air Deflector Theory  (Read 1703 times)

Offline JohnnyPopper

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Air Deflector Theory
« on: March 14, 2021, 06:07:12 PM »
So it looks like factory installed these starting in 81'?

Is the theory to keep air from going under the cab/truck thus reducing turbulence/drag?

I get that concept, when I did 125 in my Olds Toronado she lifted up about 4"!

I also see the good results from Freight Containers having the side wings.

But with these flat faced trucks, it raises a question about increasing the overall surface coming in contact with the the air.

I bought a 5" version, at high speeds it seems to vibrate.

Any thoughts would be appreciated.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: Air Deflector Theory
« Reply #1 on: March 14, 2021, 07:24:20 PM »
These were available for all years and served as an air dam as well as a way to hide the ugliness of the front suspension. I had one and it made no difference on my 1980 other than hid the control arms a bit.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline JohnnyPopper

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Re: Air Deflector Theory
« Reply #2 on: March 14, 2021, 08:57:25 PM »
Thx VZ, the earliest I could find was for a '81, so I made the leap and bought it. Doesn't really fit my '78 bumper profile perfectly.

I think I'm going to remove it and see if the vibration goes away.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 75gmck25

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Re: Air Deflector Theory
« Reply #3 on: June 22, 2021, 12:37:34 PM »
I ran across one of those "what changed each year" articles for square bodies and it said the front deflector under the bumper was not available until '81.  That was the same year they made some other front end changes, so it makes sense.

Offline JohnnyPopper

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Re: Air Deflector Theory
« Reply #4 on: June 22, 2021, 03:01:24 PM »
Ahhh, thx!

Found out the vibration was a smoked inner right front bearing, that I had just paid a shop to repack before a trip to WA. Can't find good help these days.... ::)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Stewart G Griffin

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Re: Air Deflector Theory
« Reply #5 on: September 12, 2021, 07:31:02 PM »
i think even with the large frontal area of the trucks, the air dams net gain of directed air around/under the truck out weighs any increase in the overall frontal area?   i don't think the factory would have put it on there if there was no gain?


i hear that you can make big gains by blocking off the grill.   Remember a few years ago the silverados had shutters on the grill that would open/close depending on your speed and cooling needs?

Offline JohnnyPopper

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Re: Air Deflector Theory
« Reply #6 on: September 13, 2021, 02:57:07 PM »
That makes sense Stewart. How would you block off the grill? Plexiglass behind it? Would the lack of air flow cause overheating?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: Air Deflector Theory
« Reply #7 on: September 13, 2021, 06:02:43 PM »
I ran across one of those "what changed each year" articles for square bodies and it said the front deflector under the bumper was not available until '81.  That was the same year they made some other front end changes, so it makes sense.

I don't think anyone reproduces the 80 and older air dam but it definitely existed, that article is not correct.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline Stewart G Griffin

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Re: Air Deflector Theory
« Reply #8 on: September 15, 2021, 06:05:00 PM »
That makes sense Stewart. How would you block off the grill? Plexiglass behind it? Would the lack of air flow cause overheating?

i think chloroplast and zip ties might work good.   But you have to be very careful so as not to block off too much air.   i don't think we would want to block the grill off completely.

Offline SilverMiner

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Re: Air Deflector Theory
« Reply #9 on: September 15, 2021, 08:25:13 PM »
Thx VZ, the earliest I could find was for a '81, so I made the leap and bought it. Doesn't really fit my '78 bumper profile perfectly.

I'm the owner of a 1980 K10 Suburban, and my original air dam does not attach to the bumper. Rather, it is tied to the the lower radiator support. It appears to be designed to force air both above in front of the radiator as well as below the front 4x4 axle. I can't find any GM part number for that deflector prior to 1980. Judging by the photos in old brochures, the 1981 and newer air dams are different, but it is difficult to tell.