KMiata – Belt Tensioner

A quick note at the top: For this to fit you’ll really want the KMiata Intake Manifold. You MAY be able to hog enough material out of the throttle body spacer, which interferes with the alternator side spherical bearing, but the KMiata manifold has plenty of room for everything.

I love the simplicity of KMiata’s 4-pulley setup, but I’m not really happy with the tensioning setup. I’ve no doubt that it works, but hear me out: the K24a2 alternator bolts in with 3 bolts, perpendicular to the block. In a stock configuration, there’s a big, sprung(?) idler / tensioner pulley in the system. Since that’s gone, this setup uses washers you can see in the pictures between the alternator and water-pump housing to set the tension. Servicing any part of the accessory drive involves removing the idler pulley and, in my case, 10 washers (3 on each alternator bolt plus an additional C-shaped washer I made for the top bolt to put the last bit of tension the belt). Reassembly involves dealing with those 10 washers and putting the idler on at the same time without stripping any bolts or losing a washer.

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That works fine (…ish…) if you’re doing this in a clean workshop. I can’t help but picture myself trying to fix an alternator or water pump in a wet / dirt / gravel / grass paddock space at a track or on the side of a mountain, and losing half of those parts in the dirt.

So, while I was able to get it tensioned (with the help of a pry bar and the aforementioned C-shaped washer), some more work was needed on that front. I had resigned myself at this point to simply turning up some spacers on the lathe to use instead of washers, as they’d be much easier to manage (and I could make a spare set, when it came to my attention that the Water Pump Housing from a K24z3 used a single lower bolt that runs parallel to the engine that, with some creativity, could be used as a pivot. In the stock configuration there’s a block that bolts the top of the alternator in place and it uses a sprung tensioner pulley, on the belt, but if the housing bolts up, I should be able to use that alternator and a turn-buckle style adjuster at the top to tension the belt.

Nothing’s ever that simple, however. It’s not exactly a bolt on affair.

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Problem 1 is the bolt bores are different sizes / lengths. The z3 housing uses 2 long studs (vs 1 long and 2 short), and then 1 long bolt and 1 short (vs 2 long). That’s fairly minor, I just need to grab a stud and bolt. I could honestly get by with 3 bolts, but the studs help when sliding it on the first time when it’s covered in HondaBond so I don’t screw that up horribly.

This second problem is bigger, and will require a little help from my friends. The K24z3 housing is on the left, the K24a2 housing is on the right.
The z3 housing uses 3 of the 4 bolt holes the same as the a2, but the one at the upper right (sharpie pointer) is in a different location.
HOWEVER: The hole from the original a2 pattern is *nearly* drilled through in the z3 housing so I’ve got something to work off of.

I didn’t want to have my machinist buddy go through all the trouble of milling this thing down if the hole pattern wouldn’t line up, so I used a slightly undersized drill-bit to knock the bottom of that bore out. This way, the original bore is still there to locate an endmill off of to bore it correctly.

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That top bolt is actually tight but it’s sitting on that step in the casting on the back side of the bolt. We (and by we I mean Dave) will mill in a flat for the bolt to sit flat against.

Now that I knew it fit, I could cut the big stock tensioner bracket off of the top of the pump housing and work on a turnbuckle adjustable tensioner.

After talking it over with my machinist friend, we decided to try and mount the turnbuckle adjuster to 1 of the ribs of the water pump housing. Here it is all assembled. You can see the machining in the corner for the front upper bolt, and where the turnbuckle rod end mounts.

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At full retraction of the turnbuckle (to get the belt off, for example), the engine-side rod end was binding, so I turned up a 3/8″ spacer on the lathe to add some clearance, and the action’s nice and positive.

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You can easily get the belt tight enough by hand, and then a quick tighten on the lock nuts secures it in place.

The KMiata Manifold leaves plenty of room for the adjuster, coolant and vent hoses and anything else you might want to run under the IM.

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KMiata Swap – Engine Prep

There it is, the star of the show! The Honda K24a2 from an 06-08 Acura TSX.

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The first task was to strip everything unnecessary off of it. All new wiring is going in, but I’ll likely need some connectors off of the old harness, so everything gets labeled.

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A few mods need to be made for the K-series to fit the Miata. The biggest of those is the oil pump. The a2 variant has a massive pump assembly with counter-balance shafts sitting right where the steering rack wants to live. That’s replaced with a much slimmer pump from a K20, along with a back-cover, pickup and windage tray to work specifically with the KMiata swap.

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The timing cover, chains, guides and tensioners all need to come out to get at the pump. While it was already apart (and since it was 1 extra bolt to replace it), a 50-degree variable intake cam pulley from the RSX Type-S took the place of the 25-degree sweep unit from the TSX.

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Leak testing the pan before it goes on.

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A new gasket & seals set from Honda went in to replace anything worn. The O-rings around the oil system and for the VTEC solenoids were notable in being seriously perished.

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That done, the front of the engine could go back together. Timing chain, guides, tensioner, timing cover, water pump and housing:

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Because I’m using the ATI damper, which is smaller than the stock harmonic balancer, I ended up needing to go with a shorter belt (a 6PK1035, if anyone reading this decides they need to go in a similar direction):

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I love the simplicity of KMiata’s 4-pulley setup, but I’m not really happy with the tensioning setup. As this post is long enough, I’ll dedicate a separate post to that adventure. I’ve no doubt that it works, but I can’t help but picture myself trying to fix an alternator or water pump in a wet / dirt . gravel / grass paddock space at a track or on the side of a mountain, and losing half of those parts in the dirt.

You’ll notice at some point here the engine was installed. That was a HUGE morale booster. There wasn’t much super interesting with that, it slid right in, however I do want to share a tip that’s been passed down to me from others that I found super useful: Making dowels to line up the transmission and engine.

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That made getting the transmission on SO much easier.

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Another quirk of the KMiata swap is that the starter is on the “wrong” side of the engine relative to the Miata’s, so the transmission bellhousing needs to be clearanced for it to fit:

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Next up was to start making and test-fitting cooling system parts. The lower radiator hose (a stock S2000 lower hose) was fairly straight forward:

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The upper hose seems to need to be 3 pieces. I’m still on the hunt for a single hose solution, but for now, it looks like a 72277 and a 72098 hose with a long coupler need to be used.

A 1 foot length of aluminum tube seemed to be just about perfect. A couple of passes run on the bead-roller made a nice looking piece:

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I’m going to put some more anti-abrasion sleeve and a bit of retention where it wraps around the front of the engine, because while it doesn’t touch while not loaded, I imagine when it’s full of water and moving with the car & engine, it’ll definitely rub there. Worst case it’s easy / cheap insurance that I’m not wetting down the course / track.

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Yes that’s a stock radiator. No, it won’t be in the final setup. I’m using it for mockup now to avoid dinging up the shiny aluminum one while still building this setup.

On to the other side of the motor, I can mock up the exhaust manifold. It is on the ‘wrong’ side of the engine (compared to the stock Miata configuration), so it has a crossover tube that bolts on that runs between the bell housing and oil pan.

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Unfortunately here I run into another V8Roadsters subframe issue. The crossover pipe runs into the hoop that connects both sides of the subframe and runs under the engine.

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So now I have the pleasure of taking a freshly ceramic coated to the grinder to gain a couple millimeters of clearance. Which is nice…

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So now it clears, but…ugh.

At least it won’t affect performance, or rattle every time I come off throttle.

Next up, the fuel and accessory belt systems.

KMiata Swap – Suspension

It’s time. It’s finally here. With the Chasing the Dragon Hill Climb complete (and successful beyond my wildest dreams, making the fastest pass by a Miata ever), it’s time to put the bigger, lighter Honda motor in the race car.

Unfortunately however, things got off to a rocky start. Prior to the Hill Climb I started test fitting things to the V8Roadsters subframe and all was not well.

The first bit of prep was to get the steering rack on the subframe. So as to not lose the NB rack bolts I figured I’d put the bolts into the threaded holes in the subframe for safe keeping.
3 out of 4 had powder coat completely boogering the bolt holes. Adding to the fun, the thread pitch of those holes is M12x1.25mm, which is the one M12 tap I don’t actually have in stock.
A quick Amazon shopping trip and a couple days later, the tap comes in.
After chasing the threads in the good bolt hole and 2 of the 3 bad ones, I realize 1 of the engine mount brackets completely blocks access to the 4th. Improvise and overcome right?

Turns out, a 5/16″ 12-point socket makes a good-enough narrow access tap wrench for an M12 tap.

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That’s not great, but a pretty small issue all things considered.
Then a friend (thanks Nick!) who has experience with V8R subframes suggested I check the rest of the holes, and that’s when the big problems started. I could not get the upper control arm bolts through the bores at all.

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I went as far as creating a custom tool with some rod and sand paper to grind the powdercoat out of the bores, thinking it was a similar issue to the steering rack bolts, but no, the bore was shaped like a banana. I still don’t know if it was overheated when it was welded to the frame or what, but it wasn’t great. And given that it left the shop like that, their QC wasn’t exactly giving me warm-fuzzies either.

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To KMiata’s credit, they handled getting a new one shipped out and return shipping for the bad one to V8Roadsters to ‘investigate’. Once we determined just how bad the problem was, I had a new one in hand a few days later.

And check it out: bolts that go in without any hammering or clearance! What a concept!

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Next it was time to get the steering rack prepared. Because of tight clearance to the oil pan (…a recurring theme…), all the hydraulic fittings on the steering rack housing had to be cut off. I used a 3/16″ rivet and some JBweld to seal the holes.

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Next I discovered that Mazda changed the design of their inner tie rod lock washers. The old style washers sat on the OD of the tie rod’s threads, so it was flat between the rack and the tie rod. The newer style lock washers have a shoulder that goes on the over OD of the rack. That prevents my steering rack limiters from seating all the way at the ends of the rack, taking another 3/8″ or so of travel out of the rack.

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I corrected that by throwing the limiters in the lathe to put a counter-bore in the ID to clear the washer on 1 side, but still ride nice and snug on the rack:

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Time to start disassembling the car:

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Given that I’m going to have to install and pull the drivetrain several times over the course of the coming build, I also wanted to remove the upper radiator support (which doesn’t actually support the radiator in an NA Miata), and make the front bumper bar into a bolt-on piece. As you can see, the engine and transmission will come out of the car practically straight:

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A little bit of cutting and welding later, and the front bar bolts to the chassis legs:

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It’s so much easier pulling the whole thing as a unit:

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With the rack put back together, I could finally put the subframe in the car. Unfortunately there’s evidence that my car has been in a minor front-ender, which appears to have slightly tweaked the subframe pickup points. Because of that, I had to pat my head and rub my tummy and figure out which order the bolts wanted to go in so that all the holes actually lined up, but once I figured out which hole was the furthest out and started there, it all bolted in.

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I found a couple of bad ball joints during disassembly, so I called Mazda Motorsports and re-loaded the parts cannon to get good parts on board, but once that was done, everything bolted up nice and easy (including the steering rack)

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Next, on to the KMiata specific engine mods.

Shop Project: Lift

Maff’s House of Wayward Mazdas got a huge upgrade this winter, and this one has been a LONG time coming.

I’ve been pricing and shopping and researching (and measuring my low, low ceiling) for over a year, and the right deal was there at the right time, so we pulled the trigger on a Dannmar M-6 mid-rise lift.

The plan is for a semi-permanent install of the “mobile” lift, ditching the cart for the pump and diverter valve, mounting those on the shop’s wall, keeping the wall-side post permanently installed, while keeping the option to move the off-side post sitting in the middle of the floor should the need for more space arise (like if I need to work on the trailer, as an example).

Delivery was…interesting. The freight company sent 1 guy to move the 900 lbs of lift with only a pallet jack that wasn’t actually tall enough to lift the thing. Fortunately, I have a bunch of lumber scraps so we were able to shim it, and after a mighty struggle, we got it down the lift gate, onto some furniture dollies and into the garage.

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Of course, these aren’t destined for the garage, but for the workshop. So I tore down the ‘pallet’ to get as many of the man-portable parts off and lighten the load, called a friend to help wrangle the thing, collected all my load binding gear and attached the winch to the Armada’s tow hitch.

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Carefully, ever so carefully, we backed it down the drive and into position.

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As you can see in the above picture, I’d spent some time measuring out the shop to position the posts, as they need to be plumb and square with each other. With the posts finally in the shop, I moved them into position to confirm that theory translated to the real world.

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And of course, the Miata won’t be the only vehicle using the lift, so I wanted to make sure it would fit the Dailies in our fleet.

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With everything in position, it was time to start mounting things permanently. I mounted a 2×10 to a pair of studs, then bolted the bracket for the pump and valve to it upside down, using the bolt holes for the diverter valve to mount it. I am mounting the diverter valve in the ceiling, so I didn’t need those holes and they made it convenient.

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Getting the pump mounted was a bit of a bear because it’s BLOODY heavy, but after phoning a friend, again, we got it mounted up.

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Next up were the hydraulic fittings on the posts. Those are a bit of a faff because you need to practically disassemble the post to get to the fittings at the bottom of the hydraulic cylinder. The way they’re designed, is to have 2 45 degree fittings, clocked so they’re “parallel” with each other and make an S-shape out the back of the post to clear the bolt hole back there when the hose, as designed, is installed. I am running the hoses up through the ceiling, so I don’t want that and realised, of course, that two 45s can pretty easily make a 90. Unfortunately there isn’t space at the bottom of the post for that 90 degree bend to pass through, so I had to assemble the 1st 45, put the cylinder in place in the post, then install the 2nd 45 in place down at the bottom of the post, where there really isn’t much room to work. The effort was worth it, however, as it worked a treat. Here you can see the “upgraded” quick disconnect fitting, as the ones the unit ships with are reported to be a little leaky. More a niusance than a real problem, but while I’m here installing it, $30 to fix the issue was well spent.

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I was morally certain that, with the state the shop’s structure was in when we bought the place, the floor was also certainly trash, and had planned & budgeted to cut the floor and pour new reinforced footers for the lift. With this thing holding a ton or more of weight over my head, this was not the sort of thing to take chances with.

My contractor buddy came by and we drilled a few test holes (using the posts’ bolt hole positions to do so, just in case), and found that not only was it thicker than the minimum spec required for the lift, it was in fact steel reinforced and with hard pack below it showing no signs of having settled (which would leave the concrete unsupported). A very pleasant surprise that saved a ton of time, effort and budget.

We drilled the holes and opted to epoxy the wedge anchors in (along with expanding them properly) for the full belt-and-suspenders to make sure they were secure.

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With the posts finally mounted in place, I could start working on the hydraulic connections. Doing my research I found many people who extended 1 or both hoses to the posts to remote mount the pump similar to what I’m doing. That seems problematic for 2 reasons: If you only extend 1 hose, you can end up with the lift not raising evenly, and if you extend both hoses, well…it’s bloody expensive. Some measuring showed that the hoses from the valve to the leg were plenty long enough if I remote mounted the diverter valve in the ceiling, then I would only have to have 1 hose made to go from the pump to the valve, and route the hoses to the posts down from above.

The challenge, however, is that many have reported issues bleeding air from the system when running hoses that high above the pump, so I opted to do that before mounting everything in the ceiling. This made mounting slightly more challenging, as I was going to be dealing with full hydraulic hoses, but it was worth the effort. As I was bolting the fairly heavy valve to a ceiling joist, I also made a load-spreader plate with the bolt hole pattern from the valve to put on the opposite side so that I’m not risking pulling the bolts through and damaging the joist further.

I’ll admit, the first test load didn’t put a lot of strain on the system…

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With the system bled and the hoses and valves mounted and routed up in the rafters, it was time for a real test. The lift is rated to 6000 lbs. I have a vehicle that weighs just under that figure. Let’s see if all the work we did holds!

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With the Nissan being as tall as it is, there wasn’t much head room, but it does look like I could do some minor suspension or brake work on the lift should the need arise. It’s not very high, but the lifting arms are nearly fully extended to reach the frame rails, so there was quite a torque arm on the mounts here. Given that nothing budged, I think it’s safe to say we can put this unit into service!

Job the first was to quiet a noisy power steering pump on the Subaru. There’s an O-ring prone to failure that lets air in when cold, and you need the wheels off the ground to bleed the power steering hydraulics, so why not give ‘er a go? I couldn’t get full height w/ the Subaru (I’ll likely be moving that garage door opener off to one side), but it got it plenty high to be useful for under-car work:

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And now with Papa Bear and Momma Bear having tried out the new digs, it was Baby Bear’s turn. And for that, this lift was JUUUST right. Turns out, I can actually use a measuring tape correctly from time to time!

The first full draft pull on the lift (with a load), and no clearance problems anywhere.

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Ok maybe 1 clearance problem…. I’ll need to make myself a new rolling chair, methinks, but I was pretty certain of that going into this.

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The next fun job is going to be marking out spots for the setup stands and then re-leveling those to each other, as the old spots won’t work with the lift’s position. The offside post is actually directly on where 1 of the pads went in the previous iteration. And next spring, likely, I’ll get my hands on a pressure washer and blast the old markings off of the floor. But until then, I’m going to enjoy using my new toy…er…tool!

Differential NVH Damper Delete

The NVH vibration damper on the input flange of one of my diffs has started shaking loose (a semi-common problem). Given that they’re not a critical piece, that they can be a critical failure. that they would be a royal pain to fix in the field (assuming I have access to air tools, which I typically don’t), and that I’m in the process of having them both in and out of the car before and after the hill climb, it’s time for them to go.

The piece in question is the big steel (? might be cast iron) cross sitting between the input flange and the differential housing. It’s mounted on a rubber donut bonded to the input flange.

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A few minutes on the press (for the good one, the other nearly came off by asking it nicely) and it came right off. A little time on the wire wheel to knock off the excess rubber off of the flange and it’s ready to go back in.

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I didn’t expect it would add up to much, but it did end up being a worthy gain (or loss, depending on how you look at it), taking 1.75 lbs of rotating mass off of the drive line. Like removing a small flywheel off the front of the differential. Success!

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Trailer Winch

I absolutely adore my 6# flywheel, but it does make getting the car over the hump onto the trailer a challenge. The last couple times I had to make course corrections part way up, I could smell that the clutch wasn’t happy. Since Harbor Freight had a sale going for their 2500# winch, I figured, for $50 and a bit of blood and sweat, why not?

This is my highly technical concept diagram on how I wanted to mount it. Given how short the legs are, I opted to keep both legs straight because…I had scrap pieces that were the right length 😉

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Here’s my starting point. I snagged a 6″ receiver tube, and since I didn’t have any 2″ tubing long enough, cut up a Harbor Freight 1 ball hitch:

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The black-on-black makes it difficult to see, but here is the trailer-side mount, along with the 2″ hitch welded up to the winch mounting plate:

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The trailer-side mount welded in place:

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It fits with the fuel jug, but it wouldn’t take much wiggle for it to rub, so I’ll likely end up hooking the…hook… to the back side of the receiver tube.

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I decided to run the winch off of the truck instead of having another battery on the trailer. It’s sort of a 6 of one, a half dozen of the other situation, but I mostly didn’t want to have another battery to buy, maintain, and maybe get stolen. Because of that, I needed a couple of small mods on the truck side. In the engine bay, the main things needed are a Circuit Breaker (just in case) to protect the truck-side wiring:

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About 50′ of 4 ga battery wire, and a pair of very large Quick-Disconnectors for the rear of the truck. This shows both the truck and trailer sides hooked up while I was hunting around for somewhere to put them, and discovered a very convenient M6 bolt hole on a metal bracket that secures the bottom of the rear bumper in place. It couldn’t be more perfect. The shiny bit on the right is one of the valves for the rear helper air-springs:

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After running most of the wiring for the truck (save the jumper from the battery to the circuit breaker, to keep the harness ‘cold’ so I could safely work on the wiring) it was time to work on the trailer side.

The winch comes with some pretty uninspired 10gauge wiring, so job one was replacing all of that. I’m also crimping *and* soldering all of the wire terminals. You can see the difference in size between the 4ga wire I’m running, and the stuff it comes with here.

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With all of the wiring in place, I could build the jumper between the circuit breaker and battery:

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And finally it was time to plug everything in and run a couple system checks. First off, everything was in fact dead with the circuit breaker tripped, which is a good sign. Next, plugging the winch into the truck didn’t let any smoke out. And last, I gave it a pull off of the 12,000 lb D-ring on the back of the trailer to make sure my welding is as extra medium as I thought it was. I still don’t have a ton of trigger time on it, and this is really the first thing I’ve fabbed up that could potentially kill or maim if it comes unmoored. So…I wanted to make DAMN sure the whole thing wouldn’t end up flying across the workshop. And it didn’t, so…win one for the good guys! Or…at least, for me.

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Chasing the Dragon Hill Climb is this weekend, so it’ll get some use loading the trailer at home and after (hopefully….) the event. Also: SO EXITED! 😀

LED Tachometer Mount

The main reason I got the bling-o-meter is as a rudimentary yard stick for reviewing video of speed in a certain part of the track (or at least, RPM). More lights = more fast. Easy.

The problem is that it’s nearly invisible in the video, because the steering wheel is between the tach and the camera. So how to fix it?

I noticed in the video that if it were directly behind the steering wheel on the column, it would show up perfectly, so I fabbed up a quick mount to get an idea of where it should go.

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I briefly considered welding to the column housing, but after consulting with a friend who generally knows much better than I (Thanks Dave!) decided that there’s too many important unknowns that could be cooked inside the column housing (plastic bushings, grease seals, etc) to risk welding directly to it. He floated the perfect solution (as usual). Inexpensive and effective: a 2-piece shaft collar.

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A little time on the wire wheel cleaned off the oxide coating on the un-threaded half, a little welding, and a coat of paint, and it should work great:

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A little time spent on the little things that would bother me if they were staring me in the face before each run:

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And now I should be able to get some use out of it. A little before & after: