Last updated 28 May 2009

Engine and Gearbox Choice

A great deal of time went into trawling the Internet looking at what people had already done with Spitfires, what looked good, and possibly what to avoid.  Many people have done very sensible things, the Toyota 4AGE for example, which initially looked a reasonably easy modification.  Tuning the engine within a reasonable budget seemed to take power to around 180BHP, with additional power being realised only at significant cost. 

Being stupid, male, and pig-headed I'd gotten into my head that I wanted around 200BHP, and wouldn't be happy knowing there was nowhere further to go without starting again, which ruled out the 4AGE. 

Eventually I found the Toyota Supra 7M-GE, a straight six, seven main bearings, and described as "bomb proof" once sensible torque settings were applied to the head gaskets.  The gearbox, typically the W58, also has a reputation for being able to take far more power than it was originally intended, reputedly up to 400BHP.

The 7M-GE is normally aspirated, and makes 200BHP, just what I was looking for.  It can also be tuned and turbo'd relatively easily taking power to around 350BHP, which sounds like fun, or suicide?

The deciding factor was finding an engine and gearbox on Ebay not more than 20 minutes from where I live.  The following day I spent an hour or so with a tape measure and camera, taking photos and contemplating.  I then spent the weekend walking about with the same tape measure, back and forth between the chassis, body, and a now well thumped piece of paper, convincing myself that it could be done.

Two hundred pounds and three days later the gearbox and engine were delivered and deposited next the the chassis.  It looked a lot bigger now, and the reality of what I was doing seemed oppressive. 

I now also have a 7M-GTE engine, with lower compression, under piston cooling, and a turbo.  Oh, and 240BHP.  And a complete wiring loom and ECU.  And cruise control.  The normally aspirated engine was going to need custom exhaust headers which were going to cost more than I wanted to spend.  The turbo obviously doesn't need such fancy things, at least that's my excuse, and I'm sticking to it.

Engine and Gearbox Mounts

The intention is to keep the engine as low and far back as possible. To do this part of the bulkhead, above the original opening for the gearbox, needs to be cut back. However, I did not want to cut into the ventilation intake for the heater as this adds a significant amount of strength to the body. This then dictated how far back the engine can sit, as the cylinder heads are in this area.

The gearbox fouls the chassis rails in a number of places and a number of cuts had to be made to allow sufficient clearance.  To retain as much strength as possible, especially given the increased torque the chassis must transmit, additional strengthening plates have been installed.

The original Toyota engine mounts were roughly in the middle of the engine so most of the engine weight, and torque, was taken by these.  The original Spitfire engine mounted between the suspension towers, adding significant stiffness to them.  The engine is acting as a modern day suspension tower brace.  I therefore wanted to retain this feature, but this put the mounts a long way from the original Toyota mounts.

New engine mounts were made using 5mm plate and can be seen in the photos below.

Nearside Engine Mount.  The plate on the engine will be cut back as needed later.  It has been left "as is" for the moment so it can be used to mount anything else that may be required in future.  If I cut it now I know I'll regret it later! Note that the mount is on the rear-side of the suspension tower, closer to the original Toyota mounting point.



Offside Engine Mount  This is on the front side of the suspension tower, unlike the opposite side.  It was impossible to mount on the rear-side of the suspension tower as it clashed with the oil filter, and the steering shaft.  Not ideal but I hope it won't cause any problems in future.  At the top left of this photo you can also see where I've seam welded the suspension tower.  This will be cleaned up before painting.

The original gearbox mounts gave great clearance underneath, allowing plenty of space for the exhaust.  However, they intruded excessively into the cabin, which is already spatially challenged.  I've reverted back to the original Toyota gearbox mount underneath, which will make running the exhaust fun.  At least passengers will be able to sit without a lump of metal stabbing into their legs.

Old arrangement, now abandoned:

Finally took a photo of the final set-up, from below, which has no intrusion into the cockpit.  I originally thought it would make the route for the exhaust more difficult, but actually it's no lower than other parts of the gearbox.  The mount and support bracket are the original Toyota parts, the latter cut to suit and welded in.