I thought I'd post this to the entire list. Its an attempt to
answer an few questions about my spitfire - GT6 conversion.
Unfortunatley, its a little long, so you might want to bail out...
>>Bill,
>>I was trying to recall who on the net was building the Spitfire body-on-GT6
>>chassis when you popped up with a reference to your car this week. I have
>>always felt claustrophobic in a GT6 and Spits feel a bit wimpy. You seem to
>>have the answer - a mariage made in heaven, so to speak.
>>BTW, there were two such conversions at the TRF Summer Party this month.
>>Subtle. Very neat.
>>My concerns at this point are pretty basic:
>>Are certain years more compatible for the body swap or will all fit? I'd
>>like to use an early Spit body, circa 1964-1966.
Well, yes and no. I think it would be pretty straight forward to mate
any spitfire and GT6, but there are definitely certain years and
models which are more compatible. My knowledge of the earlier spits
(mk I and II) is pretty limited. There were some pretty significant
changes between the MK III spitfire and the mk IV. Aside from the
styling changes (those early spits are pretty), the front end and
frame changed. Not significantly, but enough to give you headaches.
The eariler bonnet included the grill and had much smaller bonnet
hinges. The old and new style bonnet hinges are not compatible, nor
are the front body panels. The frame was changed in the back, but I'm
not exactly sure where. I think the shock towers were about and inch
narrower. If this is true, the body/frame mounts might have changed
too. This same transition happened between the Mk II (GT6+) and the
MK III GT6. So if you had an early spit, your best bet would be a MK
I or II GT6, if you had a mk IV or 1500 spit you would want a GT6 MK
III.
In your case, you are interested in a MK II spit. If the MK II
spit is like the mk III it would be a bolt on conversion. I just
don't know enough about the early spits to give a firm answer.
>>Are modifications to body / frame required? Extensive? Do you
>>end up with the GT6 bonnet, rather than the Spit?
There are definitely two modifications. You need to trim the
firewall on the passenger side to clear the 6 cylinder's starter and
slave cylinder. This isn't very hard. As you look at a spit
firewall, you will notice the opening is not symmetrical. All I did
was trim the passengers side until it was. Your donor GT6 will give
you the exact pattern. The rear shocks can't be mounted on the frame
uprights because they won't clear the roto-flex couplings. The GT6
has a shock mount welded to the inner wheel well. I chose to
fabricate a bolt on frame extension which moved the upper shock mount
out about four inches. I can give you the dimensions when I'm done
(I'm still working on these). The only other thing that might give
you trouble is the parking brake. The are two guides which turn the
brake cable towards the rear wheels. On my 1500 spit, they were
mounted on the frame. On the GT6 mk III they were mounted on the
body, or so I assume, since I got rid of the GT6 body before I
discovered this.
As near as I can tell the GT6 and spitfire are fundamentally
the same car. So where ever possible they used the same parts. For
example, the roto-flex suspension has the radius arm mounted
differently than the swing arm. But the holes for both radius arm
mounts were present on the spit 1500 body. The ones for the GT6
simply had rubber plugs in them. I couldn't measure any difference
between the GT6 frame and the spitfire frame as far as shape or
material thickness. The GT6 frame has extra mounting brackets for the
roto-flex lower control arms and slightly different brake line
routing.
You have to use the GT6 bonnet. The bulge is definitely
necessary to clear the radiator. I've heard stories about people being
able to keep the spit hood, but this would imply the hood could clear
the engine. I hardly think Triumph would have gone to the trouble and
expense of putting a bulge in the GT6 hood simply to clear the
radiator cap. Therefore I think the bulge is necessary to give proper
engine clearance too.
>>What other "surprises" will be encountered?
Mostly good things. You can get rid of the swing arm rear end
and get the roto-flex setup. You can argue which one performs better,
but you can't argue about the fact that the roto-flex doesn't have the
silly bearing setup found in the swing arm trunnion housing. I think
the roto-flex is an order of magnitude more durable.
You can have the vent windows found on the GT6. Vent windows in
a convertible are really great. They really reduce the buffeting off
the windscreen. They also give you enough room to install speakers in
the doors if you are so inclined - or your significant other is :-(
You'll get a serious upgrade in your braking system.
The GT6 came with a 3.12 (i think) rear end ratio as well as a
3.89. You'll be able to play around with that. (I left the 3.89 in
because I drive around town - heh heh)
The conversion is really pretty easy if you approach it the right
way. You are putting a spitfire body shell on a GT6 frame and
driveline. If you view it as trying to put the 6 banger in a
spitfire, you'll end up with a nightmare.
>>Is there some way to get an OD gearbox into the package? How about
>>a TR7 5-speed? OK, this IS getting a little "blue sky" here..... 8-)
The GT6 came with an overdrive transmission as an option. They
are worth more than their weight in gold, but you could have one. The
GT6 tranmission and rear end were really just a little too weak.
Consequently, good ones (esp. overdrives) are hard to come by. It
seems like a transmission swap from a TR6 would be more likely. I'd
say if you stroked the engine and left the 3.12 rear end in, you
wouldn't want an overdrive or a 5 speed anyway. (more on engine mods
later)
>>How about wheels? Will TR7 wheels fit the bodywork OK?
I don't know about this. If it fits the spitfire, it'll likely
fit the GT6/spit. I have a set of panasports which look very sharp,
but there is only slight clearance between the lower control arm
and rim in the rear. This might prove to be a problem later.
>>Is a TR6 engine interchangeable with a GT6 engine?
The initial casting of the GT6 2.0 liter engine found in the Mk I
was unique. I'm not sure how compatible it is with the TR6 2.5 liter.
The later GT6 castings were exactly the same as the TR. In fact you
can put a TR6 crank and rod set in the GT6 block effectively stroking
the engine. As a side benefit, the compression ratio will go up too.
All the go faster goodies availible for the TR6 will work in a stroked
GT6. The torque increase is supposed to be pretty spectacular.
Triumphtune has an article listing the gotchas. I think there are some
things to watch for in the crankshaft and flywheel. I plan to do this
after I get the Healey together
>>Is it as much fun to drive as I'd expect?
I'll let you know when I get my hood back from the paint shop and
figure out the parking brake nonsense.
I got this message later...
>>Well, that was last week. I bought a 1964 Spitfire over the weekend. Still
>>no urgency, but the interest factor has gone way up. BTW, the Spit has no
>>engine (block was allegedly cracked) so I'm looking for a 1300 long block
>>if you hear of one. I know, it's supposed to have an 1147 engine; someone
>>apparently upgraded once (the intake manifold fits a head with four intake
>>ports). I suppose an 1147 would be OK if an intake manifold came with the
>>engine. Do you know if a 1500 would be interchangeable?
If there was a 1300 engine in it (1296?), you could stick in the 1500.
You will have to get a 1500 transmission. The number of splines on
the input shaft changed. You can mix 'n' match clutch plates, but I
didn't like the clutch feel I ended up with when I did it. You will
probably trip over 1500 engines with thrown rods in the junkyards.
The 1500 ran pretty hot with all the emission stuff. You might find a
good one. My 1500 driveline is currently powering Tim Dziechowski's
midget. From his posts about squealing tires, I don't think he'll
give it up :-)
>>I should have asked about wiring the Spit/GT6 also. Anything unique there?
I'd say the wiring is dependent only on the year, not on the
model. (i.e. its the same between spit and GT6).
Enough for now? I'd be happy to answer any other questions as best I can.
woodruff@caen.engin.umich.edu
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