Project Journals

Continuing from where I left off with the other page, now that it has been filled with the full pic allotment, here's hoping for a productive 2025!

I've been working on the steering rack installation. I've "installed" both front suspensions, done a bunch of measuring and figuring and drawing, made a clever (I think!) wood fixture to hold the rack parallel to the front bar of the K-member, and I've done a bunch of tests to see where it needs to be to -nearly- zero out the bumpsteer. Rack height is pretty much what determines bumpsteer behavior, so I've set the rack a little low and added various ply shims under it until I get a setting that works - done!

So in pictures rather than words, here's the fixture and rack clamped into the car:


And from the outside, I have a laser pointer clamped onto the wheel hub, and I'm just measuring from the hub to the wheel arch as I raise and lower a jack in 1/2" bump/droop increments, and then putting a mark where the laser hits the tape on the wall up in front of the car.


Here's the pattern progress - obviously if the hub changes steering angle as it is moved up and down, then the laser will trace a sloped line/curve rather than straight up and down. I did a handful of partial patterns - the ones with a lot of slope - since I didn't need to run through the full travel to see they were way off. I've found the height I need, and I'm 3D printing dummy rack mounts right now to test before fabbing/having a laser cut outfit make them.


Weight behind the axle isn't my first choice, but if I want to sell this as a "us" project to the gal in the house, she needs to be able to sit in the car. The oil tank can't go in the passenger compartment, and it doesn't fit behind the seats between the roll hoop and the rear suspension sub-frame. So it's going out back, next to the fuel tank. Longer hoses dissipate heat, right?


...and the bracket without the tank, just tacked in place while I test fitment, angle, and make sure I'm really wanting to put it there:


Engine-wise, my local climbing-wall recovering guy has finished balancing the crank after using 9 rods to successfully narrow the big end on 8 of them. Baby steps are better than nothing, I suppose. I'd really like to get the short block together and in the car to fully evaluate the room I need in front since I've got some other parts fighting for the same space. For now there's plenty of other things to work on still!

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I've been doing a lot of work on the steering rack mount, but it's not quite done yet.

I've also been trying to get my machining tasks a little more back on track - local guy has done the crank balancing, but wants to do no more as he is downsizing and such. There's a guy 90 minutes away that has my block to put new sleeves into it, which is great - but he doesn't feel comfortable with the heads and installing oversized seats. Sooo, another guy 90 minutes away in a different direction can do that, so I'm planning to make that trip soon.

Which leads to the current priority - getting benchmark flow numbers for the stock 300 heads, before they get sent out for the new seats. I built a "PTS" style Flowbench a little while ago, but never (needed to) spent the time to get it fully functioning. It's working great now, and I'm getting repeatable numbers that are really close to what the pros have reported.

This is the bench - it's a bit smaller than others of this type, because I knew I didn't need big air capacity for the under 200-ish flow I expected to be dealing with. It's a "rationometric" design, meaning it compares two different flow-created pressure changes to each other, so there's no need for correction factors for temperature or barometer. And, unlike the Superflow design, the air passes through the fan motors after being measured, so the changing fan temps don't change the readings. Seeing what valve adjusting rigs sell for, I made my own as well.


There's a little computer gizmo available to take the place of the old-school style pressure tubes, but I haven't decided I need that yet. This one works by reading two pressure changes - the loop at the bottom is used to set fans to the flow amount to create the pressure that the port will see - 28" of water is the standard - and then the logarithmic inclined scale shows the percentage of the flow capacity of the aperture that's been installed in the bench at the moment. Superflows use a range of apertures on a turret or wheel - I have to open mine up and unscrew 4 knobs to change apertures for different flow ranges.


And my 1st attempt at harvesting data:

I have a small aperture that flows up to 93fpm, then another that goes up to 157, and a bigger one that goes to 260. I was trying to see how well they do when they overlap, and the first test wasn't great - I had an air leak that skewed things a bit. Tracked that down, applied some silicone, and things have ben getting better!

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Steering rack mount is in! This is a Miata NB rack, mounted to a NC/RX8 subframe that's been narrowed. The subframe came with some weldable steering rack mounts, but they were for a NC rack. I did repurpose the one for the left/driver side, changing the hole center spacing slightly to suit. The other end is supported out past where the subframe curves, so the mount needed to cantilever over there. The driver side carries all the side-to-side load, while the other end just sort of clamps the rack body and keeps it in line with the subframe. I played with some ideas using tubes, bent tubes, box sections, and none of them seemed to be what I thought would be best. In the end it's a fabricated 14g sheet structure which I think nicely answers all the loads, and isn't clumsy or heavy.


This is one of those things that really ought to be just right before you commit to weld. I had earlier tacked just the top plate to the subframe while I measured a bunch of stuff, and I sort of bent the plate off the welds when I was ready to start building - now, the little tack weld nubs sort of realign things for me as I put it back in as a bigger assembly.




Edited 4 time(s). Last edit at 02/17/2025 05:29PM by Roverbeam.