Gibbon's 1971 triumph GT6 that everyone told him not to mess with

[gibbon]

oh where to begin. this little car has been a part of my life for almost two decades now. one decade where it was driven, and one where it languished in it's current state. Here's a photo from better times

such a pretty, poorly designed car. anyway since another car took it's spot it's been relegated to hanging out in the workshop and generally getting in the way (luckily it's tiny). one day I woke up and thought we may as well sell it. so it looked it over, considered the rust in the sills and around the windscreen, how it's impossible to get into gear, how the brakes are jammed on, how the engine leaks like a sieve, doesn't like to start, makes weird noises when you select gears, has crankshaft play... and thought "why just sell it, when I could waste a lot of money on it and THEN sell it?" and so, this build began

The plan, aside from a general refurb, is a 1.6L NA MX5 engine and transmission swap. Nothing that I am doing here is uncharted territory. The MX5 engine is considered one of the easiest swaps and everything has been done before is documented... well, everything is anecdotally documented. ie there's a lot of build threads that encompass what I'm doing, but they all seem to skip over the nitty-gritty and focus on the successful bits. I am not a fabricator. I am impatient, and rough, and careless. I'm going to try and make a note of all the bits and pieces that I wish I had seen prior to starting this swap in the hopes that it helps the next guy

And if I totally fuck it up I'll just repost all the pictures in reverse order and pretend that I rescued the car from some butcher and restored it

 

 

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So I pulled the body. I had a GT6 "workshop manual" which was totally useless. Didn't even mention disconnecting the radius arms or rear suspension. I don't actually have a photo of it with the body off and engine still in because by the time the body was off there was pretty much nothing left to remove so I forged on and tore the motor out. only thing I had was this reference photo of the propshaft angle:

 

the motor was then removed and carefully placed on a pallet which it immediately destroyed because it is the heaviest son of a bitch I have ever come across

my phone decided to spruce up this photo, I don't know why

 

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the engine plonks on and sits between the strut towers pretty good. the stock engine mounts are no good as they cater to two nonexistent cylinders. This pic has the engine rotated a little too far, it needs to be pretty flat to clear the bonnet as of the mounting plan at this time of writing

the mx5 gearbox has some major alloy hanging off the side that needs to be dealt with as it fouls the frame. as far as I know any early rx7 tail housing will bolt on but I value money more than time at the moment so I just laid into it with a grinder and buzzed it all off. otherwise the clutch slave seems to clear OK and aside from a wee bracket on the other side, there are no clearance issues with the chassis that I can see

 

With the initial "I just want to drop the engine on it and take a photo" frivolity out of the way I stripped everything off the chassis and carefully documented everything into piles of bits on the ground and piles of bits on various tables. I misplaced all my tools but some of the other guys were away so I borrowed theirs and misplaced them too. The chassis has a few cracks and the outboard ends of the outriggers are torn, the hoist might've got them on the way up, although they didn't appear to have any cushions installed between them and the body so they might've already been pulled up hard against the underside and distorted. was hoping to get it off to the sandblasters this week but they're busy, so I had no choice but to continue fiddling around with it

 

 

 

[gibbon]

Having satisfied myself that there was nothing inherently wrong with the chassis fitment (as evidenced by others by the fact that's it's quite a common swap), most of the agonising I did was around how the engine would fit up to the body. most little triumph engine swaps end with a throwaway line like "and then I cut a hole in the body/firewall/chassis/made an ugly as hell transmission cover", which is something that I really want to avoid. so much so in fact, that I actually bothered to test-fit the body. so I'm juggling trying to avoid the chassis/bonnet/firewall, while trying to work out if I'm going to place the crank pulley over or behind the steering rack, while also being aware that the mx5 tailshaft is VERY long, putting the shifter farther and farther back, and the propshaft on a more and more marginal angle. But first, body momentarily back on;

note the battery plonked back in place as ballast to stop the bastard trying to fall off the back of the hoist

the gt6 engine mounts sit at 60 degrees and the mx5 engine mounts sit at 30 degrees. So a gt6 engine mount bracket on it's side becomes a 30 degree bracket and matches up to an mx5 engine pretty good. (did I mention I am impatient, and rough, and lazy)

str8 in m8 no fukin worries

 

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transmission fits the tunnel perfectly except the shifter is miles back, probably just about under the handbrake. No wiring was disconnected prior to this photo it was all legitimately just hanging its guts out like that since around 2012

there is a well documented mod to move the shifter forward but it's still not quite enough to get it back to the factory hole in the trans tunnel. the mod places the shifter about two inches aft of the mount points showing which would have it coming just through the wall of the tunnel.

I decided I could do better by doing away with the mount points and bringing the shifter as far forward as possible. I wish I had just gone with the original modified point! the mechanism is EXTREMELY sensitive to misaligment and the selector rod will jam up if it is not completely, perfectly straight. right now the whole thing is sitting on a workbench jammed with shims and things-acting-as-shims, waiting for some brave soul to TIG some new mount points onto it. I might get a photo of the finished product, but let's just call it a work in progress

with the aircon pulley mounted just over the steering rack and the larger alternator pully sitting just behind, this is the nearest pinch point - the heater (I think?) outlet at the back of the head just sits off from the firewall seam (pic is taken directly down at the rear of the engine). Once I'm assured that this is a heater line and nothing more I'll blank it off and move the temp probe. My heater is long gone

 

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some uninteresting photos unless you're interested - here's the current longitudinal alignment;

which results in this arrangement over the steering rack

and this somewhat tight throttle body clearance under the bonnet (with bonnet set to it's lowest) - but clearance nonetheless

 

[gibbon]

the wife and kids went away for the day so I snuck downtown for some filthy rear end action

Having being informed that the gear carrier was the weakest point of the diff, and that the diff is the weakest point of the car, it seemed the simplest solution to replace the whole unit with an "I Can't Believe It's Not Quaife" LSD. The maintenance manual talked about carefully spreading the carrier bearing caps with a Churchill tool in order to extricate the carrier, well mine just fell straight out, but I decided to not be worried about this and forge ahead. By the looks of things someone has been in here before. Another thing to do was install a drain plug, and that's already been done. It was difficult to see originally because the entire diff looked like a small planetoid consisting of mud and oil. Surprisingly had a lot of oil still in it. Going to give it the mega clean off but I'm doubtful it'll ever get clean enough to repaint it. Incidentally the carrier on this on is in good condition, perhaps it's worth something to someone

pulled the rear suspension and hubs to bits, which was shitty and greasy but not difficult. Did some research and couldn't see any truly compelling reason to not send the drums off to the sandblasters along with the rest of the bits and pieces. The buggered bushings can stay in place because I suddenly had an ancestral memory from decades ago and remembered;

I still have a set of rear poly bushes in the garage! I bought them shortly after I bought the car, did the fronts which was a huge pain in the ass, took one look at the rears and decided it'd keep for another day. Incidentally the radius arms and lower wishbones in the rear already have polybushes, guessing the previous owner was slowly replacing them as they crapped out. They actually look pretty good and sometimes I wonder if a quarter-century old bush is actually better than a modern pirate part made God knows where

pulled the rear leaf apart and wondered why it has "MAZDA" written on it, very odd. There's apparently some button guide thingies which are supposed to be between them but they are long gone

there is now a large and growing list of things that I am waiting on which is preventing anything from going back together. Ergo the only way to progress is to pull things more apart. I also have some major grudge purchases like new engine mounts, probably a clutch and a cambelt and all the other bits and pieces you really wished you did when it was in bits and easy

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extension housing finished, installed and cynically painted in a coat of hammerite direct-to-shit silver. presented on this angle which just so happens to hide every single weld, how convenient. Ended up having to ream it out as the selector rod kept getting locked up

mounts welded up and pretty much finalised, these are comprised of 80% stock triumph mounts on their side and 20% bunnings pool umbrella stand. 

chassis came back, one of my guys got to play "mark all the cracks"

uh oh. as suspected, it was definitely time for a birthday. (Also, are all chassis welds this bad under the paint?) RHS lower wishbone attach point

 

lots of other bits came back at the same time

I was having a mental health moment earlier, the diff did NOT have a drain port. It does now. 

crush tubes going in for where the mounts will sit. I guess I could have welded the brackets on directly but it might've made getting the engine back out a bit funny. Plus the chassis is so thin I'd much rather have the big bolt sandwich

Frustratingly I don't have half the suspension bushes that I need, otherwise I'd probably have the chassis repainted and all the doodads back on it this week. Also waiting on a new clutch and drive axles. 

 

 

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painted the everything the other day. I went down to the paint shop and asked for something appropriately hard for a chassis, got given a tin of chassis black. "is this that shit that never really goes off and just gets everywhere?" I asked suspiciously. "nah" said the guy behind the counter. "look, it's got 'fast drying' written on it". both the guy behind the counter and the assholes who made this stuff were full of shit. "fast drying" relative to the geological epochs involved in forming it's bitumen component perhaps, but that's about it. at least it's sprayable with a gun so I wasn't ambling around with a paintbrush dripping shit everywhere. began to get a nagging feeling that I wasn't 100% sure exactly how all this stuff goes back together. chassis has also gained an appreciable weight in entombed blast media but hopefully it'll eventually makes it's way out

 

driveshaft hoop arrived, and... oh.... at least it's another bit of wisdom I can pass on to the next guy

in fact... will the DRIVESHAFT even fit? err....

obviously the length was always going to be wrong but I was hoping i could at least be a cheapass and just cut and modify the forward end of the old shaft. the gap between the rails is 75mm give or take, and the driveshaft is pretty much exactly the same. the rails aren't perfect box sections, there's a 5mm or so overhang lip on the inboard ends, gosh I'm so tempted to just smack that down with a hammer to get the clearance

it's starting to look somewhat purposeful now at least. several onlookers have been fooled into thinking that the "hard work has been done"

sorting out the mounting for the gearbox actually took a little longer than I expected because there's just so many good places to do it, it's hard to settle on one. I eventually went off the extension housing bolts, onto a little welded block on the top of the chassis (which I think the big radio support yoke doodad bolts to?). This is largely because I forgot to weld crush tubes back here for a mount and didn't want to set three litres of tar on fire by attempting to do so now. Only really started mocking this up (Bunnings umbrella steel again) then realised it needed proper bushings. surprisingly hard to find off-the shelf spindle mounts with an imperial thread these days. BUT, easy to find mounts for british stuff. So I have a whole bunch of rubber mounts To Suit Norton Commando heading my way

Also began reassembling the suspension because I need to make this thing mobile again. Unfortunately found the polybush suspension kit for the rear completely nonfit for purpose, in fact it's totally fucking rubbish. Most of the bits are just dimensionally wrong. I rechecked the packaging and sure enough it says Rotoflex GT6, but I have been able to use about a quarter of the packet, even with modification. The control arm outer bushes are too small and literally slop around, the inner one doesnt even have a top hat/thrust section, the rear spring bushes were far too long for their steel tube (and for the spring).... just crap and I'm still pissed off about it

stay tuned for next time and I'll tell you about my amazingly silly 3d printing adventure

 

[gibbon]

we've been mad busy at work which is great for not starving to death but not great for progressing on cars

I apparently reassembled the chassis in some kind of fever dream which involved taking no photos

installed adjustable front suspension, did a lot of maths to determine the height of the correct springs to order (then knocked an extra inch off that figure because Rule of Cool) and gave the rocker cover the old Dulux Overhaul

in fact I liked it so much that the inlet manifold got the same treatment. and I cut the front off the cover Because Racecar. Note the cam gears only mocked up so as to present the illusion of actual progress while I spiral down a dumb rabbit hole of cynically repainting all the giblets

Then I broke my first rule of the build and cut the firewall:

I know, I suck!. BUT. here's how it happened. I HATED the stupid water neck at the front of the engine. It's like a leg growing out of your face. I DESPERATELY wanted more flow out the back of the head so that I could do away with the front neck. First I removed the temp sender and screwed in an extra outlet:

but the resultant total cross sectional area was still hopeless, and it'd require a really dumb collection of plumbing to bring it back together (which I absolutely would have done once upon a time). So then I got a 3d printer and played around with making a new neck: 

which was going to be super low profile but still high flow and was probably going to be made out of something extremely foolish. Fortuitously, it turned out that my measuring was garbage and the engine barely had room to even have a blank on the rear water outlet, let alone a functional outlet. So I weighed up my options, either cut the firewall (which really is just an arbitrary sized shelf section in the area that it was causing trouble), or keep the convoluted cooling system. And then I thought about all the welding and 3d designing and printing and other stuff that I'd done in the course of doing the job and suddenly chopping up the firewall was just such a minor task that I didn't even think twice about doing it

made a cover for it just because. and now there's enough room to fit a whole proper sized thermostat housing on the back! (which just so happens to be the thermostat housing from the front). Best of all, that front housing now faces the other way which will bring the return hose around the other side of the block, away from the exhaust. Then I went back and had a chuckle at my own water neck design, in the HOURS I spent on it, including re-clocking the flange angle here and there to get a higher angle over the exhaust manifold, it never occurred to me to just turn the thing 180 degrees!

So I've got cooling gubbins on the way for the side radiator inlet and everything inbetween, and am pretty much ready to drop the shell back on, but there's so much stuff that would be easier with the body off that I'm reluctant to, even though it'd earn the automotive equivalent of the roof shout. But then some of the mockup stuff is probably better done with the shell on, so you can see where there's space... 

Meanwhile on the electrical front, here's what Big Wiring wants you to think is necessary for running an engine:

but we'll see about that....

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starting to look a little bit more purposeful now although really I just dropped the body on it

I removed the (cant remember what it's called) air bypass doodad on the inlet manifold BECAUSE RACECAR, printed a cover for it which happens to look exactly like the wrinkle painted manifold. leading some to believe that the manifold itself was printed, a falsehood that I made no effort to dispel on the ground that it made me seem very talented

also made a box for the ECU which is a speeduino thing that I grabbed for the starion a million moons ago. It slots in under the battery tray. it was constructed by a shifty foreigner over covid so my mileage may quite literally vary 

this is the original front water neck, relocated to the rear of the head. I garked it out with a dremel machined it to accept the stock thermostat. clearance is still extremely tight

i also bought these lovely cannon plugs because I wanted to have a quick-disconnect loom, only to realise I dont need them as the rear of the engine and most of the loom actually sit inside the cabin anyway and it would be trivial to unhook it from the ECU directly

this is just a quick update as I realise I've also done quite a bit of other bits and pieces but not taken photos. I also have begun to notice a considerable decline in quality and standards as I slip into 'git er done' mode

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I should add that at this point I showed the car to my wife, who hadn't seen it since I took it to the workshop. she was confused and said it looked the same as it always had?

Suddenly understood that this is why some guys date other guys