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Nick's US-spec GT6


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Update time! The gearbox guy warned me in August that he had a lot of work on, and he wasn't kidding. My W58 only came back a couple of weeks ago. New bearings, seals and at least one synchro, and $1200 later it's as good as new.

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Before it goes back on the engine and in the car, I'm taking the opportunity to sort out three annoying issues. Only three, I promise.

(1) The Conversion Components kit to mate a Toyota gearbox to a Triumph engine included a clutch thrust bearing carrier, but I was never happy with it. It works, but the carrier slides too far forward on the sleeve around the gearbox's input shaft. It hangs almost halfway off, and I'm worried that as the brass bearing carrier wears, it'll start to tilt and hang up on the sleeve. The solution is to make the W58's sleeve about 13mm longer, which will take some welding and machining. The thrust bearing is also spaced forward on the brass carrier, and again it isn't as well supported as I'd like. 

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Hopefully both problems can be fixed by a clever machinist. The alternative would be a concentric clutch slave cylinder, but I'm not sure any of the Toyota-specific kits available would fit my Toyota - Triumph hybrid without some machining. And if anything goes wrong with a concentric clutch cylinder, the engine and gearbox would have to come out. Again.

(2) Before the engine came out, it occasionally made a rapid tapping noise that I could feel through the clutch pedal. Theory A was some part of the dodgy clutch mechanism contacting the flywheel, but no, that's all clear. Theory B was something in the timing gear, maybe the vernier camshaft sprocket's little bolts coming loose. No, they were fine. So Theory C is that the stainless windage tray in the alloy sump is getting tapped by a big end. I haven't put the engine on the stand to drop the sump yet. I don't want to disturb the timing because...

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(3) Camshaft timing. I never got around to adding a camshaft position sensor when I first got it on the road. They aren't strictly necessary, but they help with programming and controlling sequential injection. I couldn't add one to the vernier sprocket, because the adjusting bolts stick out further than the little flying magnet. I didn't want to try a pickup on the camshaft's redundant fuel pump lobe, as that would have involved machining the camshaft fuel pump lobe. It's a pretty rare camshaft, a gift from Andy Thompson with PI race history (overkill but sounds awesome and is still very torquey). Running a camshaft sensor on a cut-down distributor introduces uncertainty from the gear drive. But, a few months ago I was watching a Power Nation video on building an EFI Chrysler Slant Six, and they fitted a camshaft sensor to a steel camshaft sprocket.

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So that's what I'll do! It means going back to a non-adjustable camshaft sprocket, but standard sprockets have a bit of adjustability depending how they're mounted, and to be honest, I doubt a degree or so will make a difference that I can feel. Something about the perfect being the enemy of the good...

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So, watch this space...

Edited by GT6 Nick
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How very excellent to see a post from you Mr Moore! :smile:
 

Confirmation that not only are you alive and kicking but still working on perfecting the mallard monster.

Watching your clutch works with interest as I need to revisit this on my Vitesse W58 conversion although I’m don’t think there are many common parts between the two.

 

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5 hours ago, GT6 Nick said:

Running a camshaft sensor on a cut-down distributor introduces uncertainty from the gear drive.

How much would you reckon this causes a variance in the timing? I opted for the cut down distributor on my Spitfire but admit I hadn't really considered accuracy losses from the gear drive.

Agree with your caution on the clutch bearing, making progress though which is always good.

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11 hours ago, RichardB said:

How much would you reckon this causes a variance in the timing? I opted for the cut down distributor on my Spitfire but admit I hadn't really considered accuracy losses from the gear drive.

Agree with your caution on the clutch bearing, making progress though which is always good.

In truth, I doubt it matters. (Although a proper engineer would want to test that guess with a sensor on the camshaft sprocket and another on a distributor body).

There's a tiny bit of backlash in my distributor gears, probably only a degree or so. If the gears are under continual load from the oil pump, even that tiny amount shouldn't introduce errors. And again, I'm trying to avoid the perfect being the enemy of the good. But in this case, a magnet on the camshaft sprocket is an easy solution.

I'll also weld a crank angle sensor bracket to the timing cover while it's off. A bit of crackle black paint and it'll look factory.

 

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Thanks Nick, makes sense. I do like the idea of the magnet on the cam. The distributor sensor worked great with hardly any effort but it does look a bit odd. Please do share a photo or two once you've got it made up.

Messing around with injector timing settings once the engine is running sequential is interesting. The changes are very subtle and I got to the point where I thought I probably need a more sensitive way of measuring the angle.

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  • 2 weeks later...

A workmate recommended a local machinist and fabricator, Metal Mik. Mik's workshop was a showcase in metalwork. A custom Model A chassis here, an English wheel in the corner... I showed him the clutch thrust bearing mechanism, and he’s making a longer thrust bearing carrier so that it remains stable and doesn't slide off the end of the input shaft's sleeve. A simple fabrication job, when you have a lathe, mill and block of brass.

Back in my garage, I was able to swap the vernier camshaft sprocket for a solid one. The camshaft had previously been dialled in, and I was able to bolt on the solid sprocket without disturbing the timing. Next, I drilled and tapped a hole in the solid sprocket, and made a sharp punch to mark where the hole in the timing cover should be drilled. Once the cover was drilled, I fitted the flying magnet and locktite'd it in.

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A pointy bolt.

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A locktite'd magnet.

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Unfortunately my current garage isn’t wired for my welder, so I dropped the cover off to Metal Mik to weld on an M12 nut. He’ll also weld some lugs to mount a better crankshaft sensor.

Edited by GT6 Nick
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