Future LSx builder in SE Michigan
 

Greetings all!

I'm Adam. I have a 1999 silver Miata that I'm preparing for an LS swap. It's been turbocharged for the past 2 years, but I was finally tired of dealing with all the little oil leaks, exhaust leaks, coolant leaks, and such from a hacked together homebrew setup. It did make good power, though. 230/210 whp/wtq at 9 psi, but I knew I'd have to build it to make the true power I want. At that point, I would've sunk a ton of money into something that probably isn't too reliable for the track. This is where the V8 comes in! I've already pulled all the turbo stuff off to sell and fund V8 parts.

I currently have a huge spreadsheet that I believe is everything I need (other than the daily trips I'll likely be making to AutoZone and Lowes for tools/parts/materials/paint/etc) so every time I need something from Summit, I just start tacking on V8 parts to get it to $100 for free shipping. I'm looking constantly for a 5.3 or 5.7 and a T56 (ideally an LS1 dropout, so I can get all the flywheel/clutch/shifter etc). I'm also looking for a Getrag diff in either 3.42 or 3.73. The 3.73 seems way harder to find for a decent price, though. If anyone has any tips on finding these for a good deal, let me know. I search craigslist, eBay, and car-part.com every couple hours, and LS1tech every now and then.

I still plan to run the Miata this season, so I'm trying to prepare as much as possible over summer. I picked up a spare rear subframe so I can get the diff all mounted up and ready to drop in. I'll likely get the v8r frame rails bolted up over summer, and may also start seam welding if I have a free weekend. The goal is to tear down in September, and have it running by April. I'll be running it on MS3+MS3x, and already have the wires tucked, and a full wiring diagram to adapt the LSx harness to the Miata harness and MS3 db37's. I also have a Racepak iQ3s Street dash that I'm currently wiring up, so I'm feeding data from MS3, and don't really need to change anything gauge wise when the V8 goes in.

Here's a few pictures. I plan to paint the hood silver, and I'm debating on whether or not to paint the air dam silver or leave that black.

https://www.v8miata.net/attachment.p...ine=1460553698

https://www.v8miata.net/attachment.p...ine=1460553698

It looks like a great platform to swap. Welcome!

Welcome to the madness, looks like you have a nice start. If you really don't plan on starting much major work until september, hold out and get the parts that you want!

Have you consider the 8.8 over the getrag?

Yeah, it's nice that I have so much time to plan and collect parts. That way I won't make any rash decisions on purchases. I've already turned away a few potential engine purchases because they just didn't fit exactly my desired cost/condition. I'm a Test Engineer for a company that primarily works on racecars and military vehicles, so I definitely have the mindset of using quality parts and practices to create the most reliable vehicle I can.

I've considered it, yes. My thought process to why I turned it down is as follows, and in general in order of importance to me. The Getrag seems better suited for road racing, with better torque biasing capabilities. It allows more packaging room for a nice dual 2.5" setup. I believe the Getrag is lighter? A 3.42 + Stage 2 V8r setup seems cheaper than an 8.8 setup, since the swap kit is cheaper for the Getrag.

To be honest, when I saw the price tag of Getrag 3.73's, I started searching for a 3.73 8.8. I got kind of lost because the information about 8.8's is scattered across drag racing forums and such. It's not as simple as going on eBay and typing in "CTS 3.73". If the weight difference isn't much of a concern, and it's not as hard to find one as I'm thinking, I'll certainly consider it. I feel like the Getrag is a set-it-and-forget-it diff for road racers, whereas I'd look into an aftermarket LSD option for an 8.8.

I did just go to car-part.com to find an early 90's T-bird 8.8, though they don't seem to differentiate between IRS and solid, because it's giving me a bunch of Mustang rear ends as similar matches.

Feel free to convince me otherwise :)

Well first of all, there is an absolute wealth of knowledge on the subject of both rears on this forum, don't just let me convince you.

I decided on an 8.8 for a few reasons. First, they are everywhere, so that means there are tons of options. If you get that 3.73 in there and don't like it, no big deal, change up or down. As you have stated, the getrags are limited there. As far as weight and LSD goes, I picked up a aluminum housing 8.8 out of an 03 cobra. It has 3.55 gears, factory LSD (Traklock), and is around 10 lbs lighter than a standard one so its much more comparable to the getrag. On top of that, I got it for about 400 to my door, with 21k miles, so I don't have to worry about anything else but fresh fluid, no rebuilds or anything, so really I am money ahead. As far as the money goes, I am 400 into the rear, about just over 1000 for the DSS axles(with new hubs and ARP wheel studs), and I built my own mounts(Check out my thread, lots of pics), so I am less than 1500 into a mean setup, that will road race just fine.

The only downside that I came across, and you stated this, is that there is less room for routing exhaust, but I didn't have a problem with mine.

https://www.v8miata.net/attachment.p...ine=1460572350

Check out my thread

https://www.v8miata.net/general-moto...s1-2392/page5/

and itsallrigged

( https://www.v8miata.net/general-moto...ld-1903/page5/ )

Beautiful build! I am liking the sound of that. Only spending $1000 on axles and making the mounts from scratch really opens up the budget to get a nicer low mileage diff with a TrakLok. If I remember correctly, the V8r engine mount kit sits at a 1.5 degree angle, so the diff just has to match that, correct?

Honestly, If I answered that question right now I would be lying. I am only just getting my car on the ground so I have not measured that yet. Once my car is back from the shop I plan to measure/shim the rear as needed to get the driveline angle spot on. I got most of my ideas from Mike Moningers site here:

MiataV8 Conversion: Rear subframe

He is a forum member so I am sure he will chime in sometime. I made mine a little different than he did, but for the most part the same. There have been a bunch of folks use this method now.

Like I said, I wasn't trying to talk you into using an 8.8, just letting you know there are plenty of options out there.

Thanks for the link. Understood, I like to have options!

I ended up finding an assembled LS1 short block, 806 heads with valvetrain assembled, and an LS1 intake with injectors, rail, and throttle body for $300! It definitely needs oil seals, so I'm considering honing and re-ringing while I'm tearing it down. I'm trying to decide if I want to start building up the short block, or just get it running right, and worry about that later.

Time to start a build thread then?

Depends on your goals honestly. If you start getting into taking the rotating assembly out then you're talking all new bearings too. Rings, bearings, honing (if cylinders are good enough for a hone) etc etc, it all adds up. my original intention was just to "freshen up" my engine and I ended up doing a complete rebuild. It's just not a very cheap or quick process vs cleaning the block up and putting some gaskets on.