Registry: 1969 Triumph Spitfire MkIII

On my 50th birthday I purchased a1969 MK-3 with no visible rust, ok paint and a stock engine for just 2,700 dollars. Having grown up in Massachusetts and never having seen a Spitfire without rust issues at such a low price .. I had to have it. The car was a bit of a midlife crisis purchase. It ran ok but felt sluggish and needed a ton of work. I began considering ways to improve it's performance almost immediately as most Spitfire owners do. This process started by reducing weight, replacing brake components and tired suspension bits. Living in California and planning to use my car in fair weather meant that the top would be permanently removed. In Addition the glass windscreen, windscreen frame, side windows, heater, fan vents, hoses, interior carpets, panels...Jack, spare, bumpers..and all had to go. I purchased a set of aluminum racing seats with covers that weighed only 15 lbs each, threw away the tracks and bolted them down directly. The new seats minus tracks saved almost 30 lbs combined. Soon after I replaced the battery, alternator and entire wiring system saving another 17 lbs, and saying a good bye to Lucas forever. One evening I removed the door innards and decided that because I would never have a top, I no longer needed interior door latches. I weighed all the pieces and differences saved which in total came to 120+ lbs. This was my first 1st major diet for the car. I also personally lost 10 lbs getting me back to a comfortable 180.
The car was a bit quicker, and I fit better in the 15" wide racing seat. It was more responsive but was still well short of what I wanted. Looking at engine options I was also concerned with cost vs performance. In order to build my 1300 TR engine to stage 2.5 or 3 with dual DCOE Webers and all the performance parts necessary for 110hp plus would cost me at least 4500 to 5500 bucks. With the 110 hp, the car on a good day with a tail wind would reach 60mph in under 8 seconds. While that would be amazing, and almost twice as quick as the stock car, my gut told me the best thing for my Spitfire was to find a solution that would further reduce weight as well as add more power. Not too much extra power or torque, just enough. The suspension design has it's limits, the brakes are matched well to the stock car's weight. I knew that the chassis, brakes, tires and most other driveline components would function even better the lighter the car got. Like a modern day Colin Chapman, I became obsessed with "Adding Lightness". Practicality no longer mattered. I was seeking Lotus 7 performance levels and the only way to get there was to remove even more weight and find an engine specifically well suited to the concept. Light corner carving sports cars work well with high revving small displacement engines. Clearly I was not setting out to build a dragster. Monster loads of torque would not be necessary or even desirable for my concept. I needed more usable power with less weight. I set out to find an engine and trans combination weighing 200 lbs or less with about 140 hp and 70 to 80 ft/lbs torque.
After a bunch of research I began to consider Motorcycle engines. The English Locost guys where doing cool stuff with bike engines in their build's. One evening internet deep dive I found an episode of Jay Leno's garage that blew my mind. Jay had a young engineer named Matt Brown on his show. Matt had put a 900cc Honda sport bike engine in his vintage s600 Honda convertible sports car. It sounded amazing and performed great. That was it, I was all in. I emailed Matt and found his website as well as articles published about his build in process. He later would end up providing me some engineering advice in the later stages of my build. Such a cool, innovative and inspiring guy.
After watching his car videos I had to have the high rpm aluminum block engine with integrated 6 speed close ratio gearbox from a motorcycle. Ideally I would find an engine that would fit into the car without having to cut a hole in the hood. I also wanted to find a water cooled engine with carburetors that would look like it belonged in the car. Finally I found it. The perfect power source was the 1st generation Yamaha FZ-1 engine built between 2001 and 2005. From the Genesis series, this motor is low, compact, very light and reliable. With twin overhead cams, 5 valves per cylinder, it produces 148 hp from 998cc's at 10500 rpm with the red line beginning at 11500. It also provides a healthy 78 foot lbs of torque over a huge usable range. A perfect match with more than double the hp and just a bit more torque than the stock Spitfire engine. With this type of engine I could use the stock chassis, differential and most of the suspension with only a few modifications.
A week later I found a fine, used, 2002 FZ-1 engine on EBAY for just 1150 bucks complete with carbs and wire harness and only 7500 original miles. It had a compression check and a video of it running on the seller's link. It was mine.
I removed and weighed my stock TR 1300 engine in preparation for the swap. With accessories and transmission it came out just under 400 lbs. When my Yamaha engine/ trans combo arrived a week later I was able to pick it up off the shipping palette myself and put it on the scale. It weighed in at a feather light 157 lbs complete with carbs, wire harness, and starter. What a great find for my light weight cafe racer. I bought a jet kit from Ivan's so I could get rid of the stock air box and run some velocity stacks. I picked up a a heavy duty kevlar clutch kit and springs from Barnett. I had a custom 2 piece driveshaft made at a local shop. The shaft mated to the Yamaha engine with an aluminum Hawk engine adapter. I built my own motor mounts and exhaust system. The radiator is an aftermarket aluminum spitfire replacement with twin 10" fans and a shroud that I fabricated. The bike engine uses an electric, high volume, low pressure fuel pump that came on the bike, mounted in the boot and connected to the stock Spitfire tank. I also created a custom Dash that uses the FZ-1 gauge cluster and custom rod and bell crank based shift linkage with cable linkage for the hand operated clutch. With the engine and driveline based weight reduction of over 230 lbs paired with the 123 lb savings from my earlier lightening efforts, the finished car is an honest 1216.3 lbs wet. It was so light I was able to use a bathroom scale to check the corner weights for suspension tuning.
The FZ-1 bike was originally geared to achieve 150+ mph. Stock 4.11:1 Spitfire rear end gears when paired with the bike's primary drive ratio, geared the car way down and increased the mechanical advantage at the rear tires providing me with fantastic acceleration and a well suited top speed around 110 mph.
The howl of the Yamaha engine with its 11500 rpm redline is intoxicating. The car is nimble and the brakes work way better thanks to the weight reduction. The driving experience is very intense and a bit like riding in a blender at full song. I absolutely love it, but it is not for everyone. My wife refers to it as "Paul's scary old amusement park ride". I guess romantic afternoon touring with a picnic basket is out of the question in this car. It has become a stripped down, ultra light, fair weather, vintage race car for the street.
I learned so much with this project. Meeting my target cost for the project of less than $10,000 (including the cost of the original car at $2,700) took some discipline. To accomplish the entire conversion project in my home garage was not easy but achievable. If anyone is interested in more detail I am always up for a car chat / message.