Here's something for everyone (I think !): I put my Nova together with a DeWitts aluminum rad. It's a beautiful sort-of-stock appearing piece. They also included a cool billet covered rad cap. But in my "stock appearing" mindset, I decided to swap the cap for a reproduction RC15. I never thought anything of it. But when I started driving the car a bit, I was plagued with what appeared to be runaway overheating. It was frustrating, but one day when it was hot, I put a towel over the rad cap to check to see if the coolant was disappearing. No hiss. No steam. Nothing. Further investigation revealed the reproduction cap wasn't seating on the rad neck. Obviously the cooling system wasn't holding any pressure. So I replaced the repro cap with the DeWitts' supplied cap. Bingo. I can park it outside on a 90-degree day, nosed up to the garage door, put it in park, let it idle and walk away without overheating. Instant cooling fix. I wonder how many other repro caps are like this?
