Listers,
I have followed this thread with some amazement and confusion, having some
something similar a while back. It seems that while "most" of your replies
are well meaning, there is a dearth of "correct" information.
My project involved putting a TR250 frame under a TR4a IRS shell some years
ago. I am currently re-restoring the car. A club friend is restoring an
unmolested 4A, and 2 years ago I did a TR6. that is, I am familiar with
all the permutations and combinations!
First, all IRS cars share the same basic dimensions of the frame. However,
some things are hidden (i.e.: breastplate on a 4a is a single lower plate
with an upper "hoop" rearward of the plate location). A swap of 6 to 6 cyl
will be a cake walk. A swap from a 4 to a 6 will be more difficult, with
some wrinkles.
Second, the floors and sills are common to all cars from TR4 to TR6.
Third, all inner fenders are different. The TR6 uses a horizontal mounting
flange while the TR4/5 series use vertical flanges. Without major rework
(aka welding and cutting) you cannot simply bolt on TR4 fenders to a TR6.
don;t even THINK of trying this on the rear of the car as every single piece
is different to accommodate the "tail fins" of the TR4.
Specific to the right inner front fender, tehre is indeed a cutout notch but
this is primarily for the PI system. the early TR250 shells may not have
this as they never came with carbs (and there are so few TR5's and they were
a "stopgap car" anyway). they did, however, have shorter inlet manifolds.
you will fins it impossible to fit a long runner late TR6 manifold and head
to a TR 250 unless the inner fender is notched. Look at the air cleaner to
fender gap on a pre vs. post 72 car to see what I mean.
The cutouts in the inner valence are common to TR5, TR 250 and TR6. The
Tr4/4a never had them, they were e for additional cooling and (perhaps)
airflow to the optional oil cooler. This may be due to the more shrouded
profile of the TR6 grille.
As earlier stated, the mountings for ALL 6 cyl cars were the same so this is
not an issue. the TR4 series car had a different cross brace fore of the
motor and aft of the fan held with two, not three bolts per side.
Converting a 6 to a 4 causes clearance problems and engine mount problems
(but why would you put a 4 in anyway)
Finally, I am confused about the hybrid part. Bud, do you intend to run
the TR6 rear fenders, etc? One thing about the 2 cars (having owned both
for a long time) is that, while the dimensions are similar or identical,
the TR6 is much more "square rigged". You will find the TR4 fenders and
front end will look narrow compared with the TR6 rear end - if this is what
you intend. Personal taste is just that, though.
A final note... among my readings on the history of the cars, the Karmann
design was done in (I believe) 1966 as the intended replacement - to be
called the "TR5". Some of the criteria given were a "modern line" and that
"as much of the central sheetmetal was to be retained" for cost purposes.
If only they had actually redesigned the car it could have been much
different, roomier, etc. Remember, the TR7 design was penned in 1971 by
Austin's designers, and that was a clean sheet design. Might we have had a
big brother to the spitfire line with a V8 in '71 or '72? Jonmac,if you're
there, any comments as to what might have been?
Dave (searching through the cobwebs of my Triumphdom memory) Terrick
Winterpeg.
PS I will be offline until Monday but will deal with errata and flames
then...I'm off to an invitational ice race where "bastard car conversions"
are EXPECTED, not excepted.
D
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