Miata engine swap into the Triumph TR3A

This was a very agonizing decision. A few posts back I lamented the condition of the supplied engine and transmission. The straw that broke the camel's back, as it were, was a mess up with some new piston rings. You see, I was already suffering for how much money the engine alone was sapping from me (I am not a rich man). Then, after springing for the new piston and liner kit, it turns out they supplied way over sized rings. Every step of the way I had stumbling blocks in trying to get this engine built.

It was a lovely Saturday afternoon and I had resolved to make some progress. The crankshaft was fresh with the viton rear main oil seal conversion, the thrust was set precisely to spec and the main bearings plasti-gauged out and caps torqued. It was great. Then came fitting the pistons...I had several sets of figure 8 gaskets and I had shiny new 86mm jugs and slugs already fitted to my refurbished rods....then the piston rings...would not compress...the ends overlapped by a solid 1/8 inch. Madness.


Well, determined to make progress as I was, I decided I'd just grind and file the end gaps to spec (how hard could it be?). So I began. I had a start pile and a done pile. 1, 2, 3, 4 rings down, by ring 5 I somehow refiled one from the done pile, and as I test fit it into an empty cylinder, I discovered it was way too short to use...Inferno... Yeah I was mad...at myself...at the supplier for putting me in this position...at the old needy tractor engine...at the predicament. This was supposed to be a fun car to restore and own, not an expensive and difficult one. I would have bought a an old Lotus or Porsche if I wanted that kind of abuse.

I still had potentially thousands to spend to bring the engine together mechanically and cosmetically. And I still didn't know what the transmission rebuild was going to set me back (remember, I work for a living). I reasoned that in the short term, if I could find a modern donor car with a good power train for under $1500, I'd have turn-key reliability, no-nonsense driveability, less leaks, less pollution, less smoke potential, less overheating potential, less frustration. (That and I could skip on rebuilding the scary crusty corroded side-drafts that I'd been ignoring since 2010). If I could also do this without hacking away at my freshly restored frame and restored body, all the better!

This was not an easy decision, and I  still have a heavy heart, but I soothe myself in the fact that the Triumph engine wasn't really a Triumph engine. Massey-Ferguson? The ethic of the TR3 for the day was to provide the best bang for the buck and it did it with exceptional style and with that inexpensive and reliable block. I respect that engine and am taking nothing away from it's racing prowess or glorious legacy.

If the original Triumph engineers could have provided an aluminum, twin cam, cross-flow head for less money, do you think they would? If they could have added sequential fuel injection? A crisp and precise 5 speed transmission? I think they would have. It is in that spirit that I nixed the original engine and found the best engine I could for the money to power my TR3A.

 This 1994 Miata had 135k miles and a salvaged title due to a rear end accident. Never-the-less, I bought it in San Jose, Ca and drove it home that day the 150 miles or so to Sacramento. I drove it for the next month daily because it was so much fun! These cars are awesome driving, pure sports cars. I paid $1100 for this donor car.

 The 1994 is a 1.8 liter, so I am not losing or gaining any displacement. The engine management is OBD1, which allows me to forgo the installation of a catalytic converter and still keep the check engine light off.

 This is the most compact package I was able to find. Most small engines are found in front drive platforms, making the swap cumbersome. Check out that factory header!!

 Here's the wiring from the Miata to go with the engine. Much of this was cut out prior to fitting into the TR3,  what is pictured here includes airbags, lighting, heater, etc...As a bonus, there is no electronic theft deterrent system to contend with.

 After a scrub the transmission shines again. Now I will have overdrive!

 There's no way I'm lifting the hood and reading this. In 1994 the valve covers has raised letters embossed on the aluminum. Subsequent years, the letters were depressed into the aluminum

 So, with the 1994 engine, one can grind away the identity...

...And re badge just as the original Triumph developers did. Tell me this doesn't look like a little lotus engine!