Here we go again - is there a FAQ for this (Triumphs) list? (Roger, could you
cobble this into a web page for the Team.Net tech info?)
The best, bar none, 7" round headlights in the world right now are the Marchal
H4 "flat face" lamps. Unfortunately, they are no longer manufactured, and are
getting rare and expensive (the only source I know is charging more than $200
each).
What makes these lamps so very good is that they have a razor sharp low-beam
cutoff; unless the fog is *very* thick, you don't need any auxiliary lamps
(assuming that you've aimed the headlights correctly, of course).
After that, I would choose a Cibie Z beam, and then a Cibie "E Code". These can
be had in the US for about $90/pair. These also have a great low-beam cutoff.
There are cheaper lamps. I don't have any experience with them. I look at
lighting the way I look at brakes: it's not worth skimping a few dollars.
*Any* 7" H4 will be an improvement over the stock tungsten sealed beams. Even
the sealed halogens (Sylvania makes them, among others) will be an improvement,
but they suffer from many of the same problems that tungsten sealed beams do -
in particular, they typically have a very poor reflector design.
One thing to note is that H4 lamps are *not* legal in the US; the ancient DOT
laws against separate bulb headlamps apply, so H4 lamps are marked "for off
road use only". Most jurisdictions don't care any more; maybe one day the law
will get changed. If you care that much, use the sealed beam halogens and
accept the results.
Hella has recently come on the market with an H4-derived lamp that they somehow
claim is DOT legal. I don't have experience with these, either, but they might
be worth checking out if you're in the habit of attracting cops who are looking
for an excuse to write you a ticket.
Again, whatever lamp you choose, AIM IT PROPERLY!
Now, back the H4 lamps. Upgrade the stock 60/55 bulb - for courteous street
driving, I recommend a 100/55. If you're careful about aiming, trust your
wiring and don't think you'll attract the attention of cops, go for the 100/80
or 150/100 ... but don't come back to me when your stock wiring melts. Even if
you install relays (see below), the wiring out to the headlamps in our cars is
woefully small. I ran 100/80s for a while and the resistance out to the buckets
was high enough that they weren't appreciably brighter than the 60/55s.
If you make any of these upgrades, add relays and fuses. The stock harness runs
all the headlight current through that teeny-tiny headlamp switch, which often
comes from the factory with 18 gauge leads! If the contacts don't burn, and the
wires don't melt, you'll be getting a lot of voltage drop. Not to mention that
the headlamp circuit is typically unfused - a ground fault/short here will
cause serious harness damage.
At the very least, you want a relay and fuse on the high beam circuit. The best
(and easiest!) way to do this is to buy a fused Marchal relay. They're
bulletproof, and can easily be spliced into the high beam circuit. Find some
source of unswitched 12V (brown wire, you want a heavy one). Find the
blue/white wire leaving the dip switch (usually there's a connector that
connects the switch, the lead out to the lamps, and the indicator - this is a
good spot). Connect the brown wire to the source terminal on the relay. Connect
the U/W wire coming from the switch to the coil. Connect the U/W wire going to
the headlamps to the load. Make a good coil ground. Voila! You now have
brighter high beams, even if you didn't change the lamps. (If you're
particularly anal, check out
http://triumph.cs.utah.edu/sol/tech/LucasColours.html and wire the harness with
appropriate colors - I would use blue/slate for the lead that splices from
relay to the headlamp wire). Use heavy wire for the load connections - 14
gauge.
If you think about it for a little while, you can make up a neat two- or
three-wire harness and mount the relay where it's out of the way but accessible
(so you can change the fuse if it blows). In the GT6+, I mounted it on the
firewall with all the other relays; there's a good source of hot at the
overdrive relay, and it was easy to pass the two-wire harness through one of
the existing grommets.
Now, if you're having fun, you can rig a parallel relay for the low beams. If
you're going to do this, then consider not using two Marchal relays, but two
unfused relays, sharing a single source, which you fuse. Lucas makes a very
nice metal relay with a separable plastic base - you can snap the bases
together to make up a multi-unit block, and there is available a fuse holder
that snaps to the end (holds a modern blade-style fuse). These are all
available from British Wiring.
We can go on to auxiliary lamps: wire driving lamps so they're triggered by the
high beams, so they dip together. Wire fog lamps so you can turn them on with
just the parking lamps. Use relays and fuses. If you're clever and careful, you
can put it all together without cutting the original harness. My TR4A has a set
of four relays and a Lucas two-fuse box in the driver's footwell: the low and
high beams are on individual relay circuits, the driving lamps on another, and
the fourth relay is a changeover - I can select just the high beams, just the
driving lamps, or both together, when the dipswitch is in the "main" position.
It took a weekend to figure out exactly how to splice into the original
harness, but the result looks as if the factory intended it that way.
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