Do it!! No time like the present to knock out the diff install. I always find with bigger projects, especially those that feel overwhelming, it's best just to tear into them and see where it goes. I lose more sleep thinking about it vs tearing into it. I know Richard is gonna help you setup the diff, and it's super easy to r&r so get after it!

And yeah, alignment will be ballpark if you mark the bolts. It will definitely need an alignment afterwards but it should be close enough to not destroy your tires. I use whiteout (like for paper) because it sticks on quite well but can easily be removed later, since you don't want those marks to be permanent

 

Oh that痴 killer. I never saw that link on Wiseco痴 site when I was piston shopping. Thanks for the insight!

Another vote for tearing into those projects now while the car is down. Like Nate said, you値l lose more sleep thinking about it than tearing into it. Plus, the car痴 already down anyways right? Might as well knock some things out so you don稚 have to pull it apart again later once the motor痴 already in.

 

You guys are right. Less thinking and more doing.

Nate, I have the bolts marked with one of those white paint markers to keep an eye on them slipping. Those seem to come off with alcohol easy enough. As long as it is drivable for the engine break-in then it should be fine, so sounds good, I'll start undoing all of that stuff.

 

Seconding whiteout, great invention!!

Scooter gets road use, right? Depending on how much, sphericals might not be the right choice for longevity/NVH reasons. The suspension megathread has a good analysis of pros and cons of sphericals, poly and delrin, before coming down on the side of poly/bronze. I'd recommend poly/bronze for dual duty, but since Supermiata dropped theirs only SADFAB supply it, and I don't know their availability status.

 

Gee, I must admit I haven’t read the suspension mega thread before. Those are valid points and Scooter does get road use, but even when I drive it on the road it is mostly in a spirited fashion in the mountains. It is currently on poly/bronze from SadFab which work very well. I’ve had issues with them though, and one of those issues just shows up randomly and I don’t know what makes it go away (play in RLCA-O, only one side). It’s also a mess every time those need to be greased and I’m tired of that. A close friend of mine has been running sphericals in his miata for 5 or 6 years now and I’ve spent a good bit of time in that car in roadtrips, tracks and wrenching. I think sphericals would work well for Scooter as long as they last 5 or 6 years before rebuild. Maybe I’ll get tired of them by then too, as I appear to be ageing quickly haha. But agreed, I wouldn’t put those on any car that’s meant to be a comfortable and quiet cruiser.

 

Ooops, obviously missed that reference in your sig ..

You have zerks in them? Mine haven't been a problem re greasing, I certainly don't pull them apart. I had the SADFAB spherical RUCA-O in the racecar, but that was sold off in the part-out and I now have the basic poly/bronze there, haven't had any problems with them. I did think I had a problem with FUCA bushes on one side, and got a replacement pair from Sean, but it turned out to be a balljoint.

I'll follow with interest if you go with the sphericals. I would not be expecting that life around here, but YMMV, maybe you have tricks up your sleeve (sorry)?

 

haha all good. Yep they got zerks in them. I grease them twice a year and it always makes a mess in the suspension and overtime flings grease everywhere. It's also likely that I'm overdoing the grease some here.
BAHAHA I'm going to shamelessly steal that pun at some point. What makes the driving around your parts more stressful on them? Our roads here are not great, lots of holes and cracked payment, but I don't expect to put more than 3k street miles per year, and they won't see any winter driving or salt. The most street miles they'll see would be the drive to Flyin Miata, otherwise I'll just be blasting through the canyons or going to the local cars and coffee.

 

Poor roads mainly, general roughness and potholes, but I have no basis in reality for saying they are better or worse than yours - just that I have low expectations of them. But I do have 2km of dirt driveway, so 4km of dirt road every time I take the car out...

Obviously the more kms you put on them, the sooner they will show wear, I put about 8-10k kms on the car annually. I'd be concerned about water and dust ingress, exacerbated by impacts. On the poly/bronze Sean said the grease was just for that, to keep the crap out, they didn't need it for lubrication as the bushings were self-lubricated. I have probably lubed them three or four times, probably due for another now, so around every year or two. The FM have some sort of seal/dust cover but how well that works I have no idea.

I haven't seen any writeups here on them, but then I haven't been sufficiently interested in them to search for users. The bottom line is that I have made my investment in the poly/bronze, and it is working out well - so far. So I have no real incentive to go from the 'good/acceptable' to 'better'.

Nevertheless, I have an interest in 'better' as an intellectual exercise and as insurance for the possibility that the incentive emerges down the track - hence wanting to see how they turn out for you.

 

I have the SM bronze bushing suspension with zerks and agree about the messiness. I probably over grease mine as well, but it kinda get everywhere after you grease them and it's annoying to get everything clean after.

I've been happy with mine though, no play since I got the revised version from SM

 

I should add that the other thing that niggles me is the surface area - sphericals are tiny by comparison, and their surface area would be what 5%? 10%? of the bronze sleeve. The engineering and material of the bearing surfaces would be critical to their longevity (as well as the dust/water sealing), hence my interest in users' experiences.

I confess I look at the grease deposits and shrug. Maybe I am just basically a tight ****, and grease is expensive , so I use as little as I can ... Anyway, the dirt and the dust soon hide it ....

 

No updates on Scooter so far. I've been making lemonade with life's lemons lately, with the latest development being Big Bertha (i.e the Tundra) needing a new transmission. I also haven't heard back from the machine shop yet and I'm starting to get antsy and still got more parts to order based on their measurements.

Today I spent a while reading about intake runner lengths to complement the talks Emilio and I had around post #364 and #366 . Assuming the wider bore from 83.5 or 84mm pistons, and the 252 duration cams, the optimum runner length should be around 330mm to 355mm using the online calculators. Based on my understanding this measurement is from the tip of the valve to the tip of trumpet, so I took some measurements today to figure out what to do:

Borla manifold runner length: 196.85mm
Intake valve to flange: ~80.2mm (very unscientific measurement here)
Trumpet height: 50mm
Total: 327mm

That's pretty close to the minimum optimal length, and turns out to be about right for the stock engine and cams. That's what's called a happy accident. However, I would still like to have a longer intake runner closer to 355, so I'm considering a new dished backing plate that pushes the filter/airbox out 30mm, giving enough space to run 10-15mm longer trumpets. There seem to be a couple of choices for 60mm trumpets (Borla and Jenvey), because I'm now too afraid to use 3D printed trumpets on the new engine even though the first two sets held for years. From the measurements I took last time, this new backing plate should still leave enough space between the airbox and shock tower.

 

I had no clue there were calculators (hell, even calculations) that could tell you optimum runner length for ITB's. Very cool!

Sorry to hear about the Fundra trans going out. I'd much rather swap a Miata transmission lol.

 

There are two formulas I'm aware of, and I don't know which is more accurate, maybe someone here can give some input on that. I got #1 from Gemini, and #2 from a book I'm reading, Performance Automotive Engine Math.

1) The Helmholdz Resonance. The formula is L = (K/RPM) - (D/2) where, L is the length, K is the harmonic constant (132000, 97000, or 74000. Higher resonances are stronger), and D is runner diameter. All measurements in inches.
2) Don't know the name, but it was studied by Chrysler in the 1960s, L = (K * C) / N +-3 . L is length, K is a constant (they chose 72), C is the speed of pulse which changes with temperature (1100 for ease of calculation), and N is RPM. and they do a + or - 3 inches for experimentation. That's a huge difference...but the book says that in Scientific Design of Exhaust and Intake Systems a K value of 90 was more realistic, so I've been using around 88.

I do think these just get you in the ballpark, and you gotta experiment the rest. Based on the dyno day I know longer trumpets just make more power everywhere in the stock BP and that's why I want to go ahead and increase them by 10mm anyways. I could then try 3 different trumpet lengths at the next dyno day and see what happens.

Tundra: Yeah, I decided I'm not messing with that Jazz and I'm paying a local mechanic to do it. I just don't have the capacity for that with everything else going on right now.

Spoke with the machine shop today and they haven't started on the engine yet, and said the new ETA is 6 months... . No pistons or bearings ordered yet. I feel it's best to wait and do it right once, but man do I wish I had done this whole engine build on the side and still have the car running.

 

Maybe we'll get 5c00t3r going and you can co drive it this season. I honestly haven't touched it, but it should only take a few weekends to get running...

Let's see how the FD goes first, I guess!

 

Your commitment to learning understanding that knowledge is commendable. Thank god the OE's and others have run those tests so I don't have to

Bummer about the ETA from the machine shop. 6 months seems long even by these days' standards. Those guys must be busy as heck...

Nate should open up a long term rental program with all those cars he has...

 

I let Ricardo drive my 10AE last time we went out. After riding with me, he was like I don't know man, I don't have the confidence like you to huck it into a corner and slide it around like that.

1 hotlap in he's throwing into the carousel like SKREEEEEEEEEEEEEEEEEE giggling his *** off. Something about a nearly stock car makes it easy to drive like that. To be fair I owed him one, because last time he threw me the keys to scooter he saw me sliding the **** out of it, which was pretty much right after I told him "I'll take it easy"

The plan with the silver car (dubbed 5c00t3r) is to throw it together with spare parts and let the (capable trustworthy) homies take it out. Kind of a spec car.

 

Thanks Zak. I don稚 know if it痴 commendable or just dumb, but I do enjoy learning why and how stuff works. It is a very long time, and they池e very busy.

lol Nate, that was a wild day. Such a fun time in your 10AE. Once I held the first slide I couldn稚 stop haha. I kept trying to make it do the things Scooter did but SKREEEEEEE.

 

Wow, lots to catch up on here. Sorry about the engine troubles, that really sucks. I've been keeping away from the forum to avoid getting the blues about how long my own engine rebuild is taking.

I was told a one month turnaround when I brought my engine in to the machine shop in early July, and that's the main reason I decided to go through with a rebuild instead of a swap. I finally got all my parts back after the New Years holiday, and I was pretty regularly dropping by the machine shop. I gotta say, a lot can change in six months and I doubt that their timeline will get shorter. I had heard enough complaints about machine shops in general that prior to going for a rebuild, in early May bought a used JDM engine to install. On teardown, it was not at all in the condition they promised. I ended up returning it to go down the rebuild path, and had to buy the 6 speed it was paired with to avoid a restocking fee. I hope that it was treated better than the engine...

Overall, I really wish I had gone to a somewhat local Miata recycler and bought a used USDM engine to install from the get go. I may not have ended up rebuilding my original engine like I am now, but I also would have had a car on the road and actually gotten in a track day in 2025, instead of having my car apart for 8 months while waiting on machine shops, getting screwed by generic used parts resellers, and learning to assemble an engine for the first time.

 

Option, I'm sorry to hear about the hassles you went through dude. I don't respond often on your thread but I do read it and had been waiting on an update for a long time. I do believe things happen for a reason, and your build seems to have gone well!

I must say I had a fair amount of anxiety on making this build decision because I've experienced what happens when a car sits for too long. I also have seen how it can go with machine shops. That said, these dudes have a very good reputation with racing engines in New Mexico, and built Nate's engine too. I have faith in them.

No updates on Scooter...yet. But there will be updates soon. Lots going on in life, including deciding next steps for the car hobby and racing. Got to do a spec miata practice race on Sunday which was awesome. After 3 sessions I got slotted in a Miata train for the first time and that was a very big experience and highlight of the day. I want to rent a spec for a couple of races sometime, but this year will not be the year with the engine build, Tundra issues, and....you'll have to wait for the other thing. I should have updates by next week .

 

The engine builders will come through! I'm still almost more excited about your BP than my own turbo car. It's gonna sing, I can't wait to experience it.