A complete engine change brings with it so many more considerations than any rebuild or repair. One can spend hours or days pondering on how to find/make reliable radiator hoses. I know, because I did. The original TR3A radiator no longer fits because the protruding water filler neck's space is now occupied by a twin cam valve cover. Finding a suitable "off-the shelf" radiator is challenging too. Fortunately, there's not too much new under the sun in the engine swap world, so a little online research yielded some good advice. I found a page where a guy (and I can't remember what swap or who) used an aluminum performance radiator from a Honda Civic. Turns out they are plentiful and inexpensive. The Civic radiator is for a 1.8L and boasts extra cooling capacity. And it was less than $100. Score.
[Update: the inexpensive two row aluminum radiator was not keeping up with cooling demands, I purchased a more expensive 3 row Civic radiator from Summit Racing and also added a manual override switch for the electric cooling fan which have together kept the engine temp exactly where it needs to be.]
Clearancing of the right inner fender for the throttle is evident here. I had made some relief cuts, massaged the metal to it's new shape, welded, filled, sanded and repainted the area.
The problems were water neck locations and lack of hoses. Now, I can't get bogged down with all that at one time otherwise I'd never be able to move forward. I built a radiator mount adapter bracket and bolted it to the original radiator location. I installed the aluminum radiator and to that I was able to attach the Miata's original electric cooling fan. As for hoses, well, I'll cross that bridge later...
Another problem to overcome was the exhaust header. I briefly flirted with the idea of re routing the steering column to make way for the header, but that would eliminate the steering wheel mounted trafficator and horn. I even bought a few joints and bearing braces. I just couldn't do that though. I am a big fan of original steering wheels and original switches and buttons and levers, and the original look. I decided that I absolutely had to maintain the use of the original signals and horn. The only way to do that was to clearance the header to make way for the column. I did so with heat and a hammer and brute force. This was my least-proud accomplishment. Yes I saved the steering column, but at what cost to exhaust performance, and it's really a little butchery. I don't like butchery.
I had a custom drive shaft made at a place in West Sacramento. They used the original TR3 rear, cut it off, welded a new tube on, and to that they welded a new Miata front joint and yoke. Here's what both original's look like.
I shortened the transmission shift tower to get it a little closer to the stock TR3 location in the floor. There's a great article online posted by a guy who put a Miata engine in his Sprite (The Mite?), He has a step-by-step tutorial on how to modify the shifter in this fashion that I followed. Much thanks to you sir!
Fat header snakes down on the wrong side of the car...
Here's my great act of butchery. Not proud of this work, but it's a means to an end. A custom-built header may be happening in the future, but no time soon.
[Update: a year later, no performance deficiency is noted]
I also had to un shroud the steering shaft where it passed by the header.
A tight squeeze, but it is functional and importantly, I was able to keep the original steering wheel and controls.
Here's the radiator mount bracket I made from 1/8" flat stock and a little angle iron. The radiator has locating pins on the bottom and top, these I used to mount it in rubber cups on my bracket.
Bolted in place. This is nice because once again, it is quickly reversible. I didn't even have to drill holes in the chassis, they were already there!
Looks like it was made for it. I still have all-important steering box access.
This radiator is about as wide as the original TR3 one but not as tall. I think it was from a '98-mid 2000's model...
Miata fan bolted to Civic radiator. With the apron on, there is still enough room to reach a hand in and remove the radiator cap. Filling it requires an odd-shaped funnel, however.
