It appears that General Motors currently has two types of air deflectors available for the early C4 (1984-90).
Short, Non-Reinforced air deflectors (non-Z51 cars)
I assumed that my air deflector was probably original equipment and since it's an 85 and does not have the Z51 handling package, the air deflector was probably the short non-reinforced version. My air deflector was pretty badly scraped and the aluminum center support bracket was snapped in half.
I talked to Jeff Kopp about getting a new air deflector and center support bracket and he suggested that I get an upgrade kit. The kit included the left, right and center air deflector sections and it included a newer design center support bracket.
I ordered the non-Z51 version and when it arrived I discovered that I had the longer Z51 version air deflector on my car! I can only assume that an earlier owner replaced the air deflector and upgraded to the Z51 air deflector. Anyway, I installed the new upgrade (or is it a downgrade kit?) on my car and the pictures that follow illustrate the important features of the upgrade kit.
Here's a shot of the old Z51 air deflector. This is the passenger side air deflector measured on the inboard side. It measures approximately 4 1/4" in height.
Here's a shot of the new non-Z51 air deflector. This is the passenger side air deflector measured on the inboard side. It measures approximately 3 1/2" in height.
My parts book shows the original center section bracket (#18) as a "C" shaped part.
Here's a picture of the actual part snapped in half from to many encounters with parking stops.
The instructions that came with the upgrade kit show the new center section bracket (#6) as a "Z" shaped part.
Here's a picture of the actual part.
Here's the old and new brackets together.
Here's the new air deflector with center section support bracket installed. The new design is considerably stronger than the original part.
The upgrade kit included one additional bracket that was not on the car originally. An "upper" center section support bracket. It is constructed in the same fashion as the new center support bracket but it is a bit longer. This part was added to later model C4's to further strengthen the air deflector and the airfoil above it. I had to drill one 1/4" hole into the front crossmember above the airfoil and attach bracket with the supplied U-Nut and 10mm bolt. Now that everything is bolted together with the new lower and upper center section support brackets, the air deflector and airfoil are much stiffer now.
I made one little modification to the new air deflector. I drilled a 1/8" hole through the air deflector sections where they overlap. I placed a single pop-rivet backed up with a 1/8" washer there to attach the outer air deflector sections to the inner air dam section. I may dab a little black paint on the rivet head to make it disappear.
Well, there you have it! The new air deflector is installed and it probably won't scrub as many curbs, parking stops etc. since it is now approximately 3/4" shorter than it used to be.
Special thanks to Jeff Kopp (Wholesale parts manager, Superior Chevrolet, 8300 Shawnee Mission Pkwy, Merriam, KS 66202) for taking the time to help me with this project.
Give Jeff a call at 1-800-728-8267 or 913-384-3115 or email him at firstname.lastname@example.org for great prices on GM parts.
GM 1984-1990 Air Deflector part numbers:
GM 1984-1990 Air Deflector center support brackets part numbers: