A Short Article on Spitfire Specials (mostly engine swaps)
by Chris Lillja
Chris_Lillja@pupress.princeton.edu
Chris_Lillja@pupress.princeton.edu
Spitfire Specials
Factory Specials
The most famous Spitfire variants that came from the factory were the Le Mans
Spitfires. These little beauties also spawned the GT6. They had 1148cc engines
modified for endurance racing (107hp @ 7000rpm), glassed in, streamlined
headlights, fiberglass fastbacks that look a lot like a GT6, and TR4
transmissions for reliability. They won their class in 1963. They were also the
only finishers in their class in 1963. One of these racers found its way into
the hands of a privateer racer in the far east and was converted into another
famous special, the Macao spitfire. From the looks of things, they removed
the fiberglass fastback and put a hump/tailfin directly behind the driver, then
put a metal "toneau cover" over the unused passenger position. This car is
sometimes referred to a the Spitfire "Monoposto." It didn’t win many/any races
but boy does it look WAY cool…
The Triumph Herald and its derivatives, the Vitesse, the Spitfire, and GT6
have been the basis of some the coolest specials in the automotive world,
including: Amphicar (Herald engine), Bond (Vitesse chassis), Fairthorpe TX
series (Vitesse engine) TVR, TX Tripper, Hooper ’48 Spyder (Spit Kit), and AWE
pintail and Redwing (Spit Kit).
The home brew Spitfire special comes in several flavors:
Spit 6
Spit V6
Spit or GT6 V8 (SBC/F or Rover)
Ro-Spit 13A or 13B Mazda
Spitfire Kits
Spitfires and GT6’s have also been powered by Offy 255’s, various Japanese powerplants, Fiat 2000 DOHC. Possibly a TR7.
Spit 6
This is the "easiest" Spitfire conversion as the parts from the GT6 are pretty much a bolt on. Mechanically you’ll need from a "donor" GT6—Front Suspension uprights, axles and brakes. (You could use the old ones but the GT has much larger discs and heavier uprights to cope with the extra weight.) motor mounts, radiator. Oh, yeah, cut a hole in your bonnet or use a GT6 bonnet and 6cyl engine and transmission of your choice. Did I mention that you’ll have to use an intake manifold designed to fit under the GT6 bonnet? Of course the GT6 engine and transmission will bolt right in with minimal modifications. But because Triumphs are delightfully inbred you have the option of using the TR6 2.5ltr which is essentially the same block as the late GT6. Same bore, longer stroke. The GT6 oil pan, that fits the chassis, will need to be modified to accept the longer stroke. The extra torque of the 2.5 is welcome in a street motor and parts are *MUCH* easier. Unfortunately, the GT6 transmission will be marginal because of this extra torque. Rumor has it that the TR4-6 (w/o overdrive) will fit with a little modification. The Spitfire Le Mans racers used this trans.
There are some other strongly suggested modifications out back as well. The GT6 wishbone suspension, (which is often retrofitted by Vitesse owners) alleviates most of the "swing-axle" problems present in the standard set up. The GT6 3.27 axle ratio would probably make highway cruising less buzzy. I have a TR7 3.07 auto trans center section I’ve been wanting to try.
So many of the GT6 parts are recommended with this swap that most knowledgeable folks suggest starting with a GT6 whose body has seen better days and just putting Spitfire tub on top of it. You could probably do that swap in a day! Hey, you could, with the help of some quick disconnects, make a "true" convertible. Change from coupe to roadster every spring!
Not to rain on anyone’s parade, but there are some disadvantages to this swap. Namely the TR6 engine weighs about 425lbs (that’s up in Small Block Ford Land), and, when placed in a Spitfire frame, a LOT of that weight goes in front of the centerline of the front wheels. It’s not so bad in a GT6 where there’s a heavier hatchback body in the back to offset that, but it in a Spit, it does make the front end a lot heavier… On the bright side, everyone I’ve ever spoken to who’s built one says "It’s a blast!", So it can’t be that bad, and it’s still "all Triumph."
Spit V6
Barry Schwartz says there’s a better way. Barry is the "dean" of Spitfire V6 conversions. Using the Ford Mustang/Capri V6, Barry has built up a Spit that can more than "hold its own" up the mountains.
Here’s Barry’s Recipe:
The engine (Ford 2.8) is almost stock except for a mild street cam and tube headers (required for installation ). The EuroFord V6 was derived from a V4 with a balance shaft mounted in the right side of the block. Stock mounting locations were used on the frame but required new mounting brackets for the engine. GT6/TR6 engine mounts were used and cooling is handled through a custom made, four tube, large, crossflow radiator with dual thermostatically controlled electric fans. The transmission is a BORG-WARNER SR-4 MUSTANG V6 4 speed. Shortening the drive shaft the required amount for the new installation we move on to the rear end! This is the weakest part of the drive train. I blew up three carriers until I finally got it right!. I was using the stock SPITFIRE swing spring rear suspension, which is adequate if you use a carrier from a 76 or later Spitfire. . . . but I just couldn't leave well enough alone! I decided to adapt the all-independent GT6+ rear suspension. I also replaced the rotoflex joints and axles with TR6 sliding axle shafts by re-manufacturing the hubs and differential mounting flanges to accept the bigger (stronger) TR6 U-joints with axles.
See Barry’s Complete notes in Appendix B.
Appendix B
The engine (Ford 2.8) is almost stock except for a mild street cam and tube headers ( required for installation ). I had to modify the oil pan for frame clearance, which consisted of notching the front of the pan (for the steering rack) and angle notching the right side of the pan (for clearing the suspension mounting assembly). You must use the Capri rear sump pan and oil pump assembly. The EuroFord V6 was derived from a V4 with a balance shaft mounted in the right side of the block. When mounting the engine crankshaft centrally in the frame the engine will appear to be offset to the right. This is the extra material left over from the V4 balance shaft casting, the same basic casting with two extra cylinders added to make it a V6. Stock mounting locations were used on the frame but required new mounting brackets for the engine. GT6/TR6 engine mounts were used and cooling is handled through a custom made, four tube, large, crossflow radiator with dual thermostatically controlled electric fans. This car never overheats, even in the hottest weather! The intake system is basically stock with a slight modification to the intake manifold. I milled approximately 1/2 inch off the carb. mounting flange (for under-hood clearance) and removed the divider (opened the plenum chambers from two separate, into one open plenum). A WEBER 40 DFAV carb. (siamesed opening of the throttles) feeds fuel, regular 87 oct. unleaded to the engine. MOBIL 1 15-50 synthetic oil does the oiling job through a heavy duty high capacity TRW oil pump. Modifications to the bellhousing consists of machining out the area where the starter mounts, welding in a new section for mounting of the 2600 CAPRI starter (smaller than the stock MUSTANG for frame clearance), and re-drilling/tapping for the starter mounting holes (it sounds worse than it actually was). I also moved the throwout bearing actuating arm from the left to the right side of the bellhousing (again, for clearance). The stock Mustang uses a cable operated clutch and I wanted to keep it hydraulic. Moving back to the transmission, gear ratios are stock MUSTANG V6 ratios, and seem perfectly suited for the car. The transmission is a BORG-WARNER SR-4 MUSTANG V6 4 speed (the newer 5 speed would probably fit but I just haven't gotten around to finding out. I plan on installing one in the next couple of months [see footnote]). I used a Courier/Ford/Mazda clutch slave cylinder mounted on a fabricated bracket to the right side of the transmission. The only other modifications I made were to change the tailshaft extension. This was to bring the shift lever into the stock TRIUMPH mounting location. The extension used was from a 1978 AMC SPIRIT (GREMLIN). This along with the required main shaft was all that was needed. Unfortunately, this modification required making a new transmission yoke to match the rather smallish u-joints TRIUMPH uses. Mounting of the transmission was handled by manufacturing a new cross member using the 78' transmission mount. Shortening the drive shaft the required amount for the new installation we move on to the rear end! This is the weakest part of the drive train. I blew up three carriers until I finally got it right!. I was using the stock SPITFIRE swing spring rear suspension, which is adequate if you use a carrier from a 76 or later Spitfire. . . but I just couldn't leave well enough alone! I decided to adapt the all-independent GT6+ rear suspension. The modifications required were to make and weld new mounting brackets for the lower wishbones (now you can buy them), also to manufacture and weld the upper shock mounting brackets into the inner wheel well arches (you can buy these now as well). 1/4" spacers were required at the rear to clear the shocks (wider than stock tires) at the upper wheel locations hence the 49.50" rear track. I also replaced the rotoflex joints and axles with TR6 sliding axle shafts by re-manufacturing the hubs and differential mounting flanges to accept the bigger (stronger) TR6 U-joints with axles. I got real tired of replacing the rotoflex couplings about every three months! Apparently the torque of the little V6 was just too much for the rubber u-joints! As this car is constantly evolving I also just completed installing a Quaife torque sensing diff. I had to replace the 3:27 gears with 3:63 because the Quaife wouldn't accept the 3:27's. With the lower ratio I really could use the 5 speed's overdrive!
Footnote: I have installed the T5, but thats a whole 'nother page. LOTS of work, involving some frame trimming, tunnel fabrication, mod's, machining etc. but well worth it for this engine and this rear end ratio!
Spit V8
(http://www.westpro.com/Beast.html —there’s also a link to a Rover V8 Spit)
Not for the faint of heart, the V8 Spit has been around for some time now. "The Beast’s", origins go back to the early 70’s. More special, or custom, than Triumph, these "Sports Bastards" are probably some of the quickest cars around. The small block Chevy is super cheap, super reliable, but weighs almost 500lbs. The small Block Ford is 50-75lbs lighter. The important thing is that they’re short enough (almost?) to fit in behind the wheel centerline. Either one can make 400hp on pump gas, all day long, with parts you can order right now from the Summit Racing catalog, and have on your doorstep tomorrow. Heck, you can buy a complete engine, ready to go for about $2000 (just add carb and headers).
A major theme of V8 conversions is frame modifications and new or re-engineered rear suspensions. The Beast has new 2 x 2 frame members connecting the rear suspension to the frame and a Corvette IRS. An other V8 conversion I saw on the Internet cut right to the chase. This person built a completely new frame from 2 x 3 steel and hung a narrowed Ford 9" rear off the back with coil overs. No sane person would recommend a putting 400hp in a stock Spitfire chassis…
The Rover V8 is a slightly different matter. Descended from the Buick/Oldsmobile V8 of the early 60’s, this all aluminum power plant weighs only about what the stock Spit 4cyl engine weighs (it may be lighter!) and puts out 145hp in it’s mildest form. It too is capable of 300-400hp (although it takes some VERY special and expensive parts get there—but 200hp is easy). Someone evidently showed up at the Triumph factory with a very special GT6 that had this conversion. Fit like a glove in the standard frame. …But I still don’t think ANY GT6 diff could stay together at 200hp. I think the hot set up here would be the Rover V8, GT6 front spindles and brakes, and a narrowed Jag IRS.
The Ro-Spit
Any reader of Grassroots Motorsports will be familiar with this swap. The Mazda rotary is so small (it looks small in a Bugeye Sprite!) and so light (180-350lbs) that it’s been irresistible to many special builders. Tim Suddard, the editor publisher of GRM has been building a very advanced Spit powered by a Mazda 12A rotary claiming (lots of) hp. The little Rotary is helped along by an Electromotive ignition and a custom stainless header. At the rear of this Ro-Spit you’ll find a hybrid Mazda/GT6 set up which uses an early RX7 center section in a later model case, Mazda axles (no rotoflex), a custom transverse leafspring, and GT6+ uprights. This is a very serious effort. The specification also includes a full SCCA Solo I legal roll cage, racing buckets, a Tilton adjustable master cylinder assembly. This story alone justifies a subscription to GRM for the Spitfire enthusiast.
Spitfire Kits
Back in the UK, a good number of Spitfire based kits have sprung up. Since they have a separate frame construction, it’s pretty easy to bolt on a new fiberglass body to the simple Spitfire frame. Hooper creative designs make a 1948 Ferarri replica called the ’48 Spyder which I think is a replica of the "first" Ferrari. It’s a pretty complicated deal. First you strip the tub off the frame and then you add 12" to the main frame members. Steel firewalls, integral roll bars, and a really sharp looking "glasfibre" body bolts on to the resulting assemblage. A bunch have been built so far. Standard Spit 1296 or 1493 engines seem to be the most common power, but few have been built with the 2ltr six. The coolest looking one I saw used a warmed over 2ltr Fiat DOHC (Lampredi design) engine. The builder quoted a 0-60 time of 5sec.
A really neat entry is the AWE (Alan Wilkinson Engineering) Redwing and Pintail. These are "retro-styled" bodies that bolt directly to a mildly modified Spit frame. They kinda look like a Triumph Gloria SX in that they’re open fendered like an MG TD. The Redwing has "clamshell" fenders and the "Pintail" has "cycle" fenders. I want one.
I think we’ll be seeing more of these kits in the future because they kind of retain their pedigree as Triumphs if they use the standard Spit chassis and drivetrain. And since the cost of repairing a Spit tub has gotten astronomical, these conversions could keep a good number of our beloved cars "on the road" and resurrect a good many that have gone to the boneyard.
My Spit Special
My first Triumph, nominally a ’71 Spitfire MKIV (FK4084L) still resides with me in my backyard. I learned everything I know about British cars from it. It was a rolling restoration for 6 years, over which it has received a new frame (old one bent), a new body tub (old one rusted) from a ’79, totally rebuilt brakes, and a totally rebuilt front suspension. Some PO had already fitted a 1500 engine and a "rebuilt" transmission so really the "original Spit" is long gone. The only original pieces are the diff, the transmission, the boot lid, the bonnet center section, the instruments, the steering wheel, and the carb. And possibly the radiator and alternator. It is several colors. In the UK they would call it a "bitza"—a bit o’ this, a bit o’ that. I’ve struggled long and hard with the decision of what to do with the old girl. I have a TON of Spare parts including a complete new interior, a new top, complete clutch kit, extra hydraulics, a ported and polished head, twin carbs, new dist, electric fan, diff center section, Monza exhaust. If I "restore" it there’s no way anyone will believe it’s a MKIV. It isn’t legally the same car anymore so I can’t really sell it in good conscience. But I really can’t stand break it up for parts. I just can’t. During its rolling resto it chalked up several hundred miles and it never left me anywhere! HA! A perfect basis for a Spitfire Special! But which one?
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