Ram Air and the C3 Corvette Radiator

The long, slanting nose of the C3 Corvette, requires the radiator to be in as much of an aggressive angle as possible, almost 60 degrees based on my digital inclinometer readings, which makes directing ram air into the radiator, challenging.

To mitigate air loss, Chevrolet engineers installed foam rubber seals in key areas that direct ram air into the radiator, but after forty-plus years of service, those seals deteriorate to the point of becoming ineffective or go missing.

Since I was dealing with an overheating issue at the time, I was forced to look as to why this was happening, and starting from the very front of my 1976 Corvette, I chased those gremlins all the way to the Water Temp gauge in the dash and managed to learn a few things along the way.

The 1976 Corvette Assembly Manual diagram below shows the radiator seals (yellow highlights are mine), and my car had part of the ones labeled Z4 (Part No. 368682) Seal Assembly Radiator Support, and 1Z (Part No. 379987-8) Seal Upper Left & Right Hand. The letter Z indicates the seals have an adhesive backing.

I said "part" of the upper radiator support to hood seals since they did not cover the area properly, hence all those dead bugs, leaves, and twigs finding an easy way in.

Exact reproductions of the seals installed at the factory are available, but they are not cheap in my opinion, so I only ordered what I needed.

My kit included all the seals highlighted above, but instead of using the middle seal that came with the kit (I thought it was going to be too short), I ordered a 3-foot piece of 1x1-inch neoprene foam rubber from Pro Speaker Parts, an eBay seller. The total cost for that was $10.54 delivered via First Class Mail.

As the drawing above shows, the pieces are not to scale, and what appears to be a short middle piece, in reality, is almost 14 inches long. However, you will need at least two pieces measuring a total of approximately 18 inches to cover both openings, so I was glad to have plenty of 1x1-inch neoprene rubber foam on hand.


I started by measuring and cutting the pieces for the areas I wanted to cover. Again, my intention was to help keep as much of the ram air in that area and force it into the radiator. All the other seals as shown in the diagram above, plus one at the bottom, are present and were installed about four years ago.

The neoprene rubber foam I ordered measures 1x1 inches, so there was a tiny amount that protruded above the edge of the ledge where I wanted to install it. Since I didn't want to have an exposed area of sticky material exposed, I decided to cut out about 1/4 of an inch plus a sliver of foam from right behind the adhesive.

I used a sharp blade to first score the backing paper and then carefully cut out the foam. Actually, it wasn't that hard since the neoprene rubber foam is pretty dense, which made the process a lot easier.

The red arrow in the photo above shows the LHS foam in place. This will greatly enhance the distribution of ram air by directing it through the radiator.

And the photo below shows the finished product with the radiator core support to shroud upper bracket installed.

The photo above shows the RHS of the same area. The portion of foam and adhesive I removed is hardly noticeable, and not having adhesive exposed will help the area to remain clean.

The following video shows you all the steps I took to make and install my own 1x1-inch neoprene rubber foam radiator-to-core-support seals.


As I mentioned earlier, I ordered these seals from Zip Corvette Parts, and I made sure they were the right ones for my Vette which has the L-48 engine. There are lots of seals available, so make sure to get the right one for your car if you need to install new ones.

When I received mine, I have to admit that I was a bit confused as to how they were supposed to be installed. There are no instructions included and I found a little bit of information online which gave me a better general understanding.

According to the Assembly Manual, it seems they are secured by one fastener each, but the seals do not have provisions for such fasteners, although installing one would be a matter of carefully poking an awl through and then install the fastener.

The next two photos show the seals I had installed a long time ago which were too short and provided little if any help.

I then tried to improve on my design by adding "extensions" to them but, again, they did nothing to seal the huge opening between the top of the radiator support and the hood. They also looked hideous!

Factory-correct seals, on the other hand, are shaped in such a way that they reach and seal against the hood properly to block ram air from getting past the radiator and being wasted in the engine bay.

As the photo above shows, they do not have an adhesive backing as the center filler foam strip next to them, which either requires the use of a fastener or, as I chose to do, use spray adhesive so I could attach them properly and to my liking.

The next two photos show the driver's side seal being test-fitted to the top of the radiator core support. I also added a couple of small foam cubes to the ends of each seal to close a small gap between the seals and the snorkel.

The photo above shows how the seals must follow the contour of the core support to fit properly. And you can also see how they are shaped to seal the step-down portion of the inner hood.

I did not want my new seals to show spray glue overspray, so I masked them to keep the sides protected. The video below also explains and shows this in more detail.

I used 3M Hi-Strength 90 Spray Adhesive, which is labeled as "permanent." So my guess is that if I ever need to remove the seals for whatever reason—something I consider unlikely—I would need new seals.

The picture above shows the bottom edge of the seal after one coat of adhesive. However, for the driver's side seal, I decided to leave a few inches of the seal near the hood hinge free of glue since it wasn't really needed in that area. I explain and show that in the video

The photo above shows the RHS seal glued in place after spending several hours with the hood closed. You can see a couple of areas where a portion of the hood, as well as one of the hinge bolts, made impressions on the surface. This indicates that the seal is doing its job properly.

That's it for now. I hope you find this article and videos helpful.

Thank you for following my '76 Vette Blog!