This is long. I guess I am in writing withdrawal since ceasing to be a starving artist and actually working for a living.
Turns out I was able to easily remove the twist by setting the radiator on my workbench with a block of wood under one of the low corners and pressing down on the high corners until it sat flat on the bench with the block removed. One man job, but I am a big guy. As easy as it was to straighten, I can imagine the condition I received it in being a result of rough handling in shipping.
Inlet and outlet were easy to make round with the handle of a breaker bar.
Cleaned the threads for the fan mounts with a tap. Checked the fan fit, had to file one fan mounting hole slightly to make it clean.
Deburred all edges with a fine flat file. The person most likely to cut his arm off when working on the car later if you fail to do this is you, so always do it.
Ran water through the radiator with a hose for quite awhile. Recommend this highly, as I saw some silver specks come out. I assume it’s just leftover fabricating debris. I put my hand around the hose with whatever opening I was feeding at the bottom, let the water flush up through the radiator with the outlet at the top. Watched until it had been clear for awhile. Then changed the angle, shook it, reversed the flow, etc. (Kinda makes me question whether I want to buy an intercooler from this source, but I can’t imagine anything I saw being a problem for the water pump.)
On first installation, I couldn’t reach the upper rubber seats with the brackets from the core support, because the A/C condenser brackets hit the radiator. I de-angled the A/C condenser mounting brackets to tilt the condenser forward, slotting the holes to account for the change in length. I hit the tops of the condenser mounting bolts with the disc sander to shorten them and touched them up with Rustoleum engine paint (the first black can I could find) to prevent rust. Installation torque is low, so the short hexes are not a problem. The CX Racing radiator is slightly taller than the stock one. On the driver’s side, I carved away at the base of the upper rubber isolator to get rid of the flange and lower it on the stud. I slotted the hole on both brackets a little more to allow them to slide as far rearward as the tab at the bottom allowed without modifying the core support. I shimmed under the driver-side bracket with two 5/16” flat washers to finish the height issue. I ended up with about 3/16-in. of clearance between the radiator core and the condenser mounting bolts.
The hardest part was the bracket for the A/C lines. I spent some time trying to modify the stock bracket before I realized that the lines weren’t the problem, the bracket was. I made some measurements and mocked up a bracket with cardboard (empty Trader Joe's pizza box from lunch). Had to make a 1/8” adjustment (that’s why you use cardboard the first time), but got it perfect. I hit Home Despot and found a postcard-sized piece of galvanized sheet meant to reinforce a nailed joint of 2x4s for $0.98. I was able to avoid having any of the nail holes in a bad place when checking against my template. I used nut-serts to bolt up the A/C line clamps, so it’s still serviceable with just one tool – no screwing around with two wrenches and a nut that wants to do anything but line up. I only had ¼-20 nut-serts in stock, but at least the heads of the bolts are 7/16, which works with an 11mm socket. Could be worse.
The outlet for the lower hose points slightly up instead of slightly down, so there might be an issue with anti-roll bar interference when I eventually go big.
The places I trimmed the auxiliary fan were:
Took the driver’s side of the “channel” part of the lower slotted driver’s side mount off to clear the nut-sert on my A/C line bracket. Cleared the upper driver’s side fan brace even with the wire holding bracket, giving about 1/8-in. clearance to the upper radiator hose. Used a zip-tie to hold the wire on the side of the bracket, instead of on the side facing the engine. Trimmed the lower OD of the fan shroud in order to improve clearance to the anti-roll bar ( I didn't have any contact, but wanted a bigger gap). Hope it’s enough when I get a bigger bar.
The places I trimmed the main fan were:
Dressed the upper passenger side fan brace with a file to clear the stock ’99 intake duct. Had to remove some of the lower driver-side corner to clear the lower radiator hose on the outlet and what I presume are power steering lines sneaking past that corner. Fortunately, the thicker radiator did clear those lines and no adjustments were required.
The cheezy radiator cap that came with the radiator seemed to not have enough spring preload to hold the pressure it’s supposed to. I tried the stock cap on the big radiator and the cheezy cap on the stock radiator. The stock cap seems to have a little extra pressure on the big radiator, but was a lot closer than the cheezy one. Could just be more friction with the butter-soft billet aluminum filler boss. Better too much than not enough, so I went with the stock cap. I have a friend who lost an engine due to undetected gradual coolant loss through a cheezy radiator cap that came with a big Chiniator in her Silvia.
I took about ¾-in. off the upper radiator hose to account for the greater thickness. The stock intake duct does contact the upper radiator hose. I can’t really see any way to correct that prior to doing the coolant reroute (I'll be going intake side). At least they are both round and smooth and rubber.
I got everything connected, fired it up, checked for leaks, burped the hoses, got the temp gauge into the middle range. The radiator cap had begun to vent, burping air from the overflow hose into the tank. I have a few more things to do to this car before I start driving it again.
While cleaning up, I poured the coolant I’d drained out into containers for recycling, and noted that the car swallowed about a gallon more than it spit out. So there’s roughly 8 lb. of water hanging off the nose of my car that wasn’t there before, plus the extra weight of the radiator.
Summary and decision analysis:
If I knew I was going to stay naturally aspirated, I’d have stuck with a stock radiator and done supporting mods, such as coolant reroute, fan switches, and blocking all opportunities for the air to bypass the radiator or be circulated by the fans without having first passed through the radiator. I still plan to do all that, but I had to buy a radiator before the original one let go, and don’t want to do all that work and find out it isn’t enough when I eventually go turbo.
I chose this instead of a 37mm Koyo because CX Racing was $190 shipped and taxed in California, whereas the Koyo is nearly double that (don’t forget to include tax in your “shipped price” Ebay analysis). With the exclusively positive reviews in this thread, I felt good about rolling the dice. Given the increase in size, I can’t imagine a 37mm radiator not being enough cooling, and would have gone that way if CX Racing had one. But they didn’t, so I went big.
If you’re handy and well-equipped (I used an air body saw, drill press and 14-in. horizontal disc sander, as well as enough hand tools to pretty much cover my work bench), then this can work. It took basically a whole day, start to finish. This was my first significant experience working on the Miata, so I was taking time for familiarization, too. If you’re expecting to pay someone else to put this in (unlikely around here, but someone from m-dot might get lost when searching for info), don’t even think about it. The labor to fit 1 ½ inches more radiator in the car than stock will be horrifically expensive. If the Koyo or other 37mm options are more bolt-in, they will cost you a lot less in the end.
I just want to say, I love this car! I got it because I was tired of being tortured by my POS BMW. So far, it’s light years easier to work on. I might even eventually start liking to work on cars again. Everything makes sense on this car, and I keep being surprised by how easy it is, and how well-thought out. With the BMW, everything was infuriating, completely stupid, designed by a-holes who’d never worked on a car before.