C4 Corvette Radiator Swap - Trending Downward

Because of its design layout, the C4 Vette snorts more questionable stuff up its schnoz than all the cast members of Celebrity Rehab combined. As you can see here, much of it ends up on the radiator and A/C condenser, where it can block the flow of cooling air. Yank the shroud and clean the crud from these pieces at least once a year to keep your system in top operating condition.

Our favorite bit of condenser-borne detritus? This lipstick-smeared Salem Menthol butt. Classy!

The stock radiator should slide out with a minimum of effort. With it out of the way, Miller took the opportunity to de-gunk the condenser with compressed air.

This side-by-side photo helps illustrate the advantages of the Zip Direct Fit radiator (left) as compared with the stock C4 unit. The additional thickness of the Zip piece is attributable to its two-row design, which effectively doubles cooling capacity. Also note the precision-welded aluminum neck and end tank, which are virtually immune to cracking.

Prior to installation, Miller secures the included adhesive-backed foam seals to the top and bottom surfaces of the radiator. These ensure that all incoming air is directed across the radiator’s cooling fins.

As promised, the Direct Fit radiator dropped right into place.

We did have to slightly trim two of the shroud’s mounting tabs to accommodate the burly Zip unit.

The plus-size Direct Fit unit also pushes the shroud slightly rearward, creating a small gap between it and the radiator.

Not to worry: The kit comes with a heavy-duty plastic shim that plugs the opening to create a good seal.

After reinstalling the various lines and hoses, Miller uses a specialized tool to create a vacuum in the cooling system...

...then refills the system with fresh coolant. If you don’t have one of these tools, you’ll need to bleed any remaining air using the factory “weep” holes. Consult your owner’s manual for the proper procedure, and be sure to use a coolant that meets GM standard 6277M.

With the Direct Fit radiator installed, the engine bay is virtually indistinguishable from stock. We did, however, immediately notice a marked improvement in cooling under comparable conditions. In our pseudo-scientific test loop through the Tampa exurbs, coolant temps topped out at a high of 185 degrees (F) on a 75 degree day, down from a max of almost 200 with the stock unit. That reduction should translate directly into improved engine performance and increased component life, making this one upgrade that’s well worth the investment.