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GT6 GT6 MK3 Resto-Mod, Opinions Needed

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Flinkly

Jedi Trainee
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Ok,

I'm getting ready to piece back together my gt6 and am beginning to waiver on what parts I want to replace, and what parts I want to upgrade. On the whole I'm starting from an original gt6. In the end, I’d like to have a reasonably powerful gt6 for town and highway use, good gas mileage, and to improve my gt6 in safety and entertainment realms. Originality is important overall, but when I can actually improve the workings, I will.

First off, wiring harness. an original harness would be the easiest, but I’d like to change electrical components like a hi-torque starter, brighter headlights, stereo (basic), upgraded alternator (50 amp), and electric fan in place of the original. It seems like a Dan Masters harness would help me with new components, but would probably take me ages to install and get working. And they cost the same, so no easy decision there. (thinking old for ease of installation, I can always supplement with more wires and relays)

Header/exhaust. I've got an original header that is perfectly fine. I’d like to get a single large bore exhaust (no dual due to loss of hp) instead of the original restrictive. I’d be driving below 4000rpm most of the time, I assume, but want a bit more than 80hp. Biggest problem here is availability for the gt6, Rimmer is the only one who supplies a gt6 single exhaust and it comes with the header, 6-3-1 ($900). Although a header would look cool in the engine bay…

Brakes. I plan on trying to fit some Toyota calipers under the stock steel wheels in hopes that I can improve braking, as some tr6 enthusiasts have done. I haven’t picked any up yet and haven’t talked to anyone who has tried, so I’m doing a bit of “engineering” here to see what I can get. Doing this mostly because my old calipers are shot and cost 300 to replace. I’d also like to set up my rear drums with self-adjusters that the 1973 gt6 had, but that should be easy. I guess I might be talked into keeping the original brakes. Any other upgrades here I should be aware of?

I’ve got more, but I already feel like I’m being an annoyance with such a long post covering so many topics. I’d write a post for each topic, but I’m sure that would somehow be more annoying.

Oh, and I’ve already relocated the rear suspension shock onto the frame and off of the rear wheel well. I’m not sure why that was ever done in the first place, but that was a priority after I saw that on disassembly.

Oh, and one more. I have been thinking over and over about changing the dash from a gt6 setup with 3 gauges and open “glove boxes” to a tr6 setup with 4 gauges and a real glove box. I know this hurts all the purists inside, but this will be the only mod on my car so far that can’t be undone in a half an hour. I’d really love a fourth gauge on the dash and I will never install or use those dumb glove boxes on my gt6…worthless. I have been toying around with a new wood dash that fits what I want, but the metal frame doesn’t support much of a change without modification. I did grow up with woodworking…maybe I should try my hand at making my own dash first…
 
Flinkly said:
(thinking old for ease of installation, I can always supplement with more wires and relays)
Click to expand...
Assuming the original harness is in reasonable condition, that is the way I would go. You'll need to add some wires for the new/uprated components, but not too many.
 
Flinkly said:
Ok,

I'm getting ready to piece back together my gt6 and am beginning to waiver on what parts I want to replace, and what parts I want to upgrade. On the whole I'm starting from an original gt6. In the end, I’d like to have a reasonably powerful gt6 for town and highway use, good gas mileage, and to improve my gt6 in safety and entertainment realms. Originality is important overall, but when I can actually improve the workings, I will.

First off, wiring harness. an original harness would be the easiest, but I’d like to change electrical components like a hi-torque starter, brighter headlights, stereo (basic), upgraded alternator (50 amp), and electric fan in place of the original. It seems like a Dan Masters harness would help me with new components, but would probably take me ages to install and get working. And they cost the same, so no easy decision there. (thinking old for ease of installation, I can always supplement with more wires and relays)

Header/exhaust. I've got an original header that is perfectly fine. I’d like to get a single large bore exhaust (no dual due to loss of hp) instead of the original restrictive. I’d be driving below 4000rpm most of the time, I assume, but want a bit more than 80hp. Biggest problem here is availability for the gt6, Rimmer is the only one who supplies a gt6 single exhaust and it comes with the header, 6-3-1 ($900). Although a header would look cool in the engine bay…

Brakes. I plan on trying to fit some Toyota calipers under the stock steel wheels in hopes that I can improve braking, as some tr6 enthusiasts have done. I haven’t picked any up yet and haven’t talked to anyone who has tried, so I’m doing a bit of “engineering” here to see what I can get. Doing this mostly because my old calipers are shot and cost 300 to replace. I’d also like to set up my rear drums with self-adjusters that the 1973 gt6 had, but that should be easy. I guess I might be talked into keeping the original brakes. Any other upgrades here I should be aware of?

I’ve got more, but I already feel like I’m being an annoyance with such a long post covering so many topics. I’d write a post for each topic, but I’m sure that would somehow be more annoying.

Oh, and I’ve already relocated the rear suspension shock onto the frame and off of the rear wheel well. I’m not sure why that was ever done in the first place, but that was a priority after I saw that on disassembly.

Oh, and one more. I have been thinking over and over about changing the dash from a gt6 setup with 3 gauges and open “glove boxes” to a tr6 setup with 4 gauges and a real glove box. I know this hurts all the purists inside, but this will be the only mod on my car so far that can’t be undone in a half an hour. I’d really love a fourth gauge on the dash and I will never install or use those dumb glove boxes on my gt6…worthless. I have been toying around with a new wood dash that fits what I want, but the metal frame doesn’t support much of a change without modification. I did grow up with woodworking…maybe I should try my hand at making my own dash first…
Click to expand...


Very good questions, some great ideas. However, if you're truly concerned with "originality", you may toss a few of these out of the window.

Here's my tuppence worth:

1) An upgraded wiring loom is a no-brainer. It makes the car safer to operate and does not cost a lot.

2)Adding a header will not provide significant increase in power without other engine mods (i.e., port polishing; a good, free-flow exhaust system, rejet carbs, etc.) Headers are not the easiest or cheapest way to get more power, IMHO, especially if you're driving below 4,000 RPM most of the time.

3) Original brakes are fine if you're driving below 4,000 RPM and not thrashing the car regularly. In fact, if the original MKIII brakes are in good order, they're pretty good brakes for anything outside of racing/autocrossing, etc.

4) Extra gauge dashes are available on eBay (one extra gauge in the middle cluster), and if you choose a wood that's near the original French walnut, they look great (just keep the old dash). If you want more gauges, two will go nicely in the vent holes which are perfect size for 52mm gauges. For example, I put a Smith's clock in my pass. side vent hole and loved it (I kept the vent hardware).

The TR-6 mods dash you describe would, IMHO, ruin the interior and the "originality" of the car.

Your GT6 is a rare car, nice examples are increasingly harder to find. Please tread lightly on your restoration efforts: keep mods reversible and retain all your old parts. When you sell the car, prospective buyers may not want or like your mods and may not purchase a car with them.

I'm sure you'll get better answers than mine, these are just my personal opinions that come with many years of restoring LBCs.

The "poor man's Ferrari" is a favorite of mine, and quite possibly the best deal on todays collector car marketplace for a true, GT sports car.

Andrew, what do you think (Andrew Mace is one of our real GT6 gurus)?? Hopefully, he'll chime in!

Best of luck to you, enjoy the restoration journey and keep us posted! /bcforum/images/%%GRAEMLIN_URL%%/driving.gif
 
I have had show cars, and driver level cars. My opinion is 2 fold:
A.The better the shape the car the more I cared about originality. On a driver quality car I tended to do whatever the heck I wanted.
B. It is your car, do what makes you happy.

My current car has Miata seats for comfort, will soon have a 3rd breaklight, and I am doing what i want to it. My last TR7 was show quality and I kept it original.
 
I'm 100% behind Mark Brown

Patrick Langford
Wayensville, N.C.

five Spits and now looking for a GT6
 
Regarding brakes, for example, I'd first spend some effort on getting the originals as good as they can be. There are various options for more modern pad/lining materials. I strongly suggest avoiding any "upgrade" to the self-adjusting rear brakes of the 1973 model GT6, primarily because some of the bits are extremely difficult to obtain if you don't have them or they're broken. For the whopping five minutes it takes every few thousand miles to raise the rear end and give two adjusters a click or so each, it's not worth it.

Frankly, the "average" GT6 isn't exactly a slug compared even to some much more modern cars. Yes, the later "UE" low-compression engines were down a bit on power, but even they still had gobs of torque to push around what is still a relatively light car. Again here, I'd try to get the very best out of what's there before adding on random shiny bits. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
ooh, a lot more responses than when I discuss car stuff with my brother or SO. First I’d like to say it's nice to have this group of guys who really understand what an lbc is.

First, I’ve posted a bit and have a running photo archive but to clarify, I started with all original but none of it in good shape.

The original wire loom was way too cut up from PO work and rats, so I’m already starting from scratch there (the seats will probably be miata seats for now too, as they didn't survive intact either).

The header would go with the engine work that has been done, although I do still have the "original" cam that came in the engine (which makes me wonder if I really know what I have inside my engine, I hate to admit. I’ll have to check that.).

The dash does tear me up too. I know it's integral to the gt6 "look", so I hate to mess with it, but the glove boxes or the lack of really kills me. And I’m already remaking a dash to replace what once was a dash, so I can easily make small changes and already have an oil pressure gauge that came with my parts car. So I’ll do some more work with working in a fourth gauge without having to mutilate. I have seen a 1500 ignition box on a gt6 steering column though. I’d love to relocate that ignition.

As for quality of the rebuild, it will look fantastic after the new paint (leaning towards tahiti blue or mimosa yellow here) and, well, everything else being replaced, rebuilt, or renewed in some way.

Just starting to rebuild on the frame painted with por15 and topcoat of chassis black, all suspension freshly blasted and painted/cured with high temp ceramic. It will be a driver in the end, no trailer queens here. Hoping to keep it indefinitely as the last thing I need is to sell it and lose my "child". I should probably name her soon. Or maybe when she's "born".

And for toyota brakes, they were selected in the beginning to be a pretty direct replacement as apposed to an increase in power. But I should probably start with the tried and true original as much as possible and replace when I am really sure I NEED to replace it. That’s one thing I have learned from you guys on here, it’s just that I’m buying new or having some parts rebuilt, where I could be getting a “better” replacement right off the bat which leads me to being frugal and getting something “better” to begin with.

As for performance mods, I’d love to have my intake manifold tuned, but I can’t afford 300 dollars to even out the flow.

EDIT: dang, three responses before i could even finish my response.
 
I'm adding a rear sway bar to my GT6.

Last May, when I competed in the local Jaguar Club Slalom, my inside rear wheel kept lifting on the turns. The diff not being locked, I got a lot of unproductive wheel spin. Even so, my best time was 53 seconds. The best time at this event was 45 seconds by a 2003 Jaguar four wheel drive X-type. I think I can do better if I can keep the tires on the ground.

That may not seem important until you try to power out of a curved on-ramp into 75 mph traffic. The GT6 is so small you have to go like a bullet to keep from being run over.

The other improvement is an overdrive transmission. To run at 70 mph, the engine turns a 4,000 or so. That's too many turns for a 35 year old engine.

My stock GT6 with well over 100,000 miles and 1 quart in 800 miles oil consumption is surprisingly quick. I don't think I will mess with the engine until it needs it....

Boy, these cars are a blast to drive.
 
i've been wondering about that transmission. i'm assuming you've got none from the factory and run a 3.27 rear diff. the factory manual does state 20 miles an hour in top gear at 1000rpm. and 3.89 diff with overdrive at 21 miles an hour in top gear at 1000rpm. now an overdrive paired with a 3.27 diff (gt6 wheel diameter being 71.5 inches) would only bring this value up to 25 miles an hour, if i calculated right (top overdrive gear around 1.21?). it does seem like a small jump, but...

that makes 65 miles an hour at 2600 rpm as apposed to...

3150 rpm by my calculations.

although with an overdrive, you could still cruise at 3150 if you wanted, then flip the switch for increased fuel economy. now if only the math would show i could save $1400 in gas to pay for a new overdrive tranny.

on a side note, my SO's hyundai is a gt and runs at 3000 rpm at highway speeds and is by far my biggest gripe with the car. after that it's the strange steering wheel and pedal distances and a couple other odd things.
 
roger_abbott said:
I'm adding a rear sway bar to my GT6.

Last May, when I competed in the local Jaguar Club Slalom, my inside rear wheel kept lifting on the turns.
Click to expand...
But unless it was hitting the stops in the rear, adding a rear bar is only going to increase the lift on the inside rear wheel. Usually a heavier front bar reduces rear wheel lift.
 
TR3driver said:
But unless it was hitting the stops in the rear, adding a rear bar is only going to increase the lift on the inside rear wheel. Usually a heavier front bar reduces rear wheel lift.
Click to expand...
True, I suppose, but that will come at the expense of yet more understeer, not something I particularly care for on a GT6. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif (That's my perspective from many long-ago years of autocrossing my GT6+, where I also experienced the occasional inside rear wheel lift with a totally stock -- save for Konis -- suspension.)
 
Yup, heavier front bar will increase understeer. And I'm not saying that's the right way to go, to get a GT6 around the track quickest. Just that IMO it helps to have a clear idea up front which problem you are trying to mitigate, and how move in that direction. Picking a problem and making it worse is probably not the right thing to do.
 
ok, so i'm going to go ahead and rebuild the stock calipers myself and keep the transmission i've got for now. these things can always be replaced later, so i might as well get it out on the road first and start enjoying it.

still torn on which wiring harness to purchase and what exhaust system would be acceptable for present and future modifications. i'm not worried about biggest bang for buck at the moment, just interested in things that can accept the changes i plan on making later so i don't have to get a new exhaust system again. But this won't be used for racing.
 
I think your time & money would be better spent on the typical upgrades.

1. Do the usual hot rod stuff to the engine, especially if you've got a Mk3. The compression is low on the US Mk3, & by decking the block & shaving the head (Kas Kastner's competition manual is a good place to go for most of this info), even just to the UK spec of 9.25 or 9.5:1, you'll get somewhere that's more fun than crack. If you then drop a dime on a hotter road cam (the US cam is also tamer) like Isky's Z-19, you'll start getting to the point where the fun worries you.

2. Since all that head & cam stuff was to meet US emissions specs, you'll obviously be using the car only off-road anyway. So you might as well ditch the CDSE carbs, which are really fine but have a very limited needle selection. Find some CD 150 carbs (and a GT6 Mk2 intake manifold), & you can get some needles that will get the most out of your increased compression & hotter cam.

3. Buy & install an overdrive & a 3.89 Spitfire differential. If your car has no overdrive, it has the 3.27 differential which gave it an easier lope on the highway. The 3.89 differential was common in many US Spitfires, is a direct swap, & will give you quicker acceleration. On the highway, you then activate the overdrive & get a final drive that's even lower than the one with the original 3.27 diff for better economy.

4. The standard brakes are fine. I wouldn't even spend money on slotted or drilled rotors for the front. Even modern factory racers don't use them, & they are more prone to fatigue & breakage. Don't bother with some rear-disc installation either: 60% or more of the braking is biased to the front, so it doesn't buy much there. Also, disc brake setups are heavier than drum brake, so modern showroom stock autocrossers of most makes if they have a car that had rear discs as an option make sure they've got drums at the rear.

It's important when going through the brakes to make sure you've got the right combination of hydraulic cylinders. These changed with development through the years, & with the addition of a brake booster, with variations in the bores of the master cylinder & slave cylinders. Don't mix & match between setups, use a caliper on the bores before installation. A lot of places sell "one size works for all", & that isn't true, & some places may send you the wrong one. It's important get get familiar with the specs of the cylinders, know which ones you've got, & keep all that under control.

5. Tighten that suspension up with modern poly bushes. Their drawback is that they give a slightly harsher ride (& all of us who've been through the phases of hotrodding a small sports car know that can make for an unenjoyable road/everyday car in a short time). But they come from different suppliers in different degrees of firmness, & reports are that Chris Witor's are just right. Since you're doing a body-off, I'd see if you could get some of the rubber body bushings (between the frame & tub) in poly.

6. You'll also want better shocks for handling. I've had my Koni's on for about 20 years, the orange paint is almost all gone from the right front, they've been excellent from the time I finally got them adjusted just right. However, I vividly recall the adjustment period, because to adjust Koni's, you have to take them off & crank them, put them back on, check the response, repeat. If I had it all to do over again today, I'd get some Avo shocks of which reports are great AND they're externally adjustable.

Since you've relocated the mounts for the rears, remember that you won't be using the stock replacement length of shocks there & you'll have to measure & figure out what to ask for. Honestly, I think there's nothing wrong with the stock shock mount location as long as you're not hammering it all the time at the track. You have no idea what I've put my GT6 through in my earlier days before I began to treat it better - miss an exit on the interstate so just rip a U-turn across an unpaved median at 70; skid & handling tryouts at speed in the wet & dry on airfields & big parking lots, etc.; the mounts are fine. I dunno how. I even hit a 4x4 that was laying across the road one night with the right rear, it BROKE the Koni shock I had there first, bent the wheel, just generally tore up & necessitated replacement of everything back there - hub, brakes, stub axle, shock, & trailing arm, but somehow the shock mount was fine whereas the shock broke. I've never thought of that before.

7. Lower the car & you'll get even better handling, if you can adjust to speed bumps at .5 mph. You can get lowering blocks from many suppliers, & you can get shorter & stiffer front springs from almost any speed shop aftermarket spring supplier if you give them the specs.

8. Get some fatter rubber. Your GT6 may have the 4.5j wheels. Later Spitfires had identical-looking wheels that were 5j. If you go for sparkly alloys, 5.5j is about as far as you can go without cutting up the fenders or looking a little funny-car-ish.

9. Clean up the ignition with a Pertronix replacement for the points. It makes a big difference. Also, there are very good reports of the 123 Distributor, which has no points, & has selectable advance curves. The 123's drawback is that it has no takeoff for the GT6's mechanical tach, so you'll have to fit an electronic tach if you go that way.

10. Leave the open glove compartment. The best thing about the open GT6 glove compartment is that thieves can see that there's nothing in there. I had a lot of junk in the parcel shelves of my GT6, & fortunately the thief broke only the vent window to get in. I thank him for breaking only that, as opposed to breaking the big door window, or pulling out the door glass & f'ing up the door & window tracks. I would still knock him around for stealing my original owner's manual, though. Leave the open parcel shelves, don't put stuff in them, store anything that stays in the car back with the spare. You'll be amazed how much stuff goes back there as you jam more in & have to organize more. Don't lock your car. If you've got the walnut shift knob without the shift pattern, a hot-wire guy will never find reverse anyway.

(If the condition of the dash is a problem, I got a new dash in 1987 from a restoration company named Keller Associates at 2262 Weston Drive, San Jose, CA. I defy anyone to tell it from an original, down to the white lettering in the correct font, except that it looks just as good today as when it came out of the box. I don't find Keller Associates in a web search; they may have changed their name or gone away.)

11. For an extra gauge, replace the temp gauge with one of the nifty same-size same-look Smith's dual oil/water temp gauges. I've had one for decades, & it's excellent. Spitbits sells them for as reasonable a price as they come. If I were to add a voltmeter, I think I'd just hang it under the dash in another wire holder like the eyeball heater/fresh air vents.

Most of the stuff I've collected about mods is in the wiki at
https://www.britishcarforum.com/tikiwiki/tiki-index.php?page=Triumph+GT-6+Modifications

Trust me, I've gone through about the same curve of hot-it-up with the GT6, although a little earlier, & this is the path to take. As you just focus the attributes of the car tighter, it becomes even more GT6-y and an incomparable ball of fun.
 
My GT6 has a 3.89 differential. First gear is so high that it feels like I am starting off in second gear on a normal car. So, I reason that I should retain the present differential and add the overdrive transmission to gain road speed at reasonable rpm's. I have an overdrive transmission that came out of an earlier ('69? 70?) GT6. I doubt I will ever drive this car far enough to pay the relatively modest cost of this transmission, even a $3.00 plus/gallon. I just want the engine to keep turning.

On the rear sway bar, maybe I am making a mistake. I thought the function of a sway bar was to reduce body roll. However, my research into this rather murky subject seems to indicate that to correct understeer, increase the diameter of the rear bar or decrease the diameter of the front bar, and vice versa for oversteer. Part of the problem may be the relatively soft rear spring. So, it's an experiment.

It's still a blast to drive.
 
roger_abbott said:
My GT6 has a 3.89 differential. First gear is so high that it feels like I am starting off in second gear on a normal car. So, I reason that I should retain the present differential and add the overdrive transmission to gain road speed at reasonable rpm's. I have an overdrive transmission that came out of an earlier ('69? 70?) GT6. I doubt I will ever drive this car far enough to pay the relatively modest cost of this transmission, even a $3.00 plus/gallon. I just want the engine to keep turning.
Click to expand...

Do you mean it's laboring to get moving from rest in 1st? Or do you mean that it feels like you get up to a 2nd gear-type speed immediately when in 1st?
 
Not to make (too much) light of all this talk about "high-revving" GT6s, but....

It's quite apparent that many of you have never had the pleasure of driving an early single-carb Herald 948 with it's 4.875:1 diff and stump-puller first gear. The twin-carb 948 or Triumph 10, both of which had 4.55:1 diffs and the same gearbox, weren't much better in this regard. In fact, Owners Manuals for all of the above suggested that first gear was not necessary for a level start from rest!

Meanwhile, I never felt at any time that either of my GT6s (+ and Mk3) felt stressed at all at highway speeds. 3000 rpm @ 60 mph is not exactly screaming. (For that matter, 4000 rpm @ 65 mph, which is about what the Herald sees, isn't all that bad, either!)
 
There's long been a tradition of hearing that the best differential for a GT6 w/OD is the 3.63. However, few of those made it to the US, but there were many put in UK Spitfires.

The cost of shipping a differential from the UK to the US would likely be huge, but you could look into it if you're putting together a topnotch GT6. I suppose you could also see about just having the innards shipped over & assembling them into a diff case here.
 
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