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SVreX
SVreX MegaDork
12/11/17 7:31 p.m.

I want a V8 Miata.  I can't afford to buy one already built.  I'm only a mediocre builder.  I've never built an engine, am pretty good with suspension, body, detailing and finishing, and minor fab work.

I seem especially good at collecting unfinished projects.  I don't want that to be the legacy for this car.

If I had my choice, I'd have an NB or NC with an LS and a T56.  My max budget is about $5K (and I'd rather do it for Challenge money), so there are gonna be some compromises.  I want to build a GREAT clean street driver- 300hp or so.  Manual trans is a requirement.

I already have the makings for a pretty good start:

-94 NA in good condition.  Rust free, dent free.  Leather interior, new soft top, 1.8L (apparently with a 6 spd).  Torsen, mildly upgraded suspension.  Only thing wrong with the car is sticky lifters and cosmetic.  Oh... and its an NA!

- 4.8L LS with 243 heads, a GM hot cam, car oil pan, car intake, GM computer, auto trans.  Also have nitrous setup, and a few other goodies.  Some assembly required.

Total invested in Challenge dollars for the car AND the engine together is about $200 (after recoup).

But I am missing that elusive budget-friendly T56 that we are all looking for, and the rear diff swap is sounding a little daunting...

 

I had an opportunity to buy a complete running Mustang recently with a great engine, and some good parts.  Deal fell through, but it got me thinking...  My 300 hp target is well within the reach of a 5.0, the 5.0 swap is really well documented, a T5 will bolt up,  and starting with a complete running donor car would give me most of the parts I need.  The documentation and the complete running donor seem to be an easier path for someone like me with limited skills.  Besides...5.0's really do sound great with a nice set of Flowmasters!

So, I've been looking for Mustangs...

I know the LS is the better option (and the 4.8 could be a really nice revving motor with it's over-square design), but the 5.0 seems to be a much easier route.  Am I right?

I'm going to look at a complete running 95 GT tomorrow that looks promising.  It's got a built 5.0 that needs tuning due to recent installation of bigger 24 lb injectors.  Aluminum Holley heads, GT40 intake, MSD ignition, Lunati street/strip roller cam, hyraulic lifters, harden pushrods, forged internals, long tube headers.  New clutch and cable .x pipe with flow masters. 3 row radiator.  They want $2500. It would put me over Challenge budget for the entire project, but not by much.  

So, my questions...

- Is the build learning curve really much easier with the well-documented 5.0L swap?

- Will I be building a compromise that makes me wish I waited and built the LS powered car?

- Will I regret the NA- should I keep looking for an NB?

- If I keep it near 300 hp, can I survive (at least for a while) with the stock Miata rear end?

- Should I just drive this car and enjoy it?

- Will I wish I just built a turbo Miata again?

 

What does the hive think??

 

G_Body_Man
G_Body_Man UltraDork
12/11/17 7:40 p.m.

Why not just use a used Nissan CD009 with an LS adapter plate? Way cheaper than a T56. Also, IIRC an FC Turbo II LSD is good until at least 400 HP and should fit nicely.

Knurled.
Knurled. MegaDork
12/11/17 7:45 p.m.

IMO, the main advantage a V8 Miata has over a regular Miata is that it handles better than a Factory Five and is a hell of a lot more livable, and it is a ton cheaper to build.

 

OTOH, a V8 Miata isn't nearly as rev-happy as a stock 1.6 Miata.

 

I'd take a 1.6 with a 5.5" clutch over a V8 anyday.  But everyone's different.

SVreX
SVreX MegaDork
12/11/17 7:49 p.m.

In reply to Knurled. :

I like the NA for it's simplicity and light weight.  I'm just not really a fan of the pop-up headlights.

bmw88rider
bmw88rider SuperDork
12/11/17 7:50 p.m.

In reply to G_Body_Man :

Shifter location mostly. That is a long distance from the bellhousing edge (~39.5") where as the Fbody T56 used in miatas is 10"shorter. Add in the width of the adapter and the shifter would be in the mddle of the armrest. 

oldopelguy
oldopelguy UltraDork
12/11/17 7:51 p.m.

If the T5 will hold up to the 5.0 it will hold up to the LS. Similarly, at autocross speeds a T-10 or AX-15/MA-5 will work well with a numerically lower (taller) rear end to tighten up the ratios.

Corvette ZFs aren't all that expensive these days either.

SVreX
SVreX MegaDork
12/11/17 7:51 p.m.
bmw88rider said:

In reply to G_Body_Man :

Shifter location mostly. That is a long distance from the bellhousing edge (~39.5") where as the Fbody T56 used in miatas is 10"shorter. Add in the width of the adapter and the shifter would be in the mddle of the armrest. 

Yuk

SVreX
SVreX MegaDork
12/11/17 7:55 p.m.
oldopelguy said:

If the T5 will hold up to the 5.0 it will hold up to the LS. Similarly, at autocross speeds a T-10 or AX-15/MA-5 will work well with a numerically lower (taller) rear end to tighten up the ratios.

Corvette ZFs and all that expensive these days either.

That's true.

I guess I figured if I took the time to build an LS powered Miata, the T5 would seem like kinda a "WTF" choice.  Like I cheaped out and didn't do the proper T56.   I'm not closed to it, but I like matched pairs of engine/ trans combos, and I think I may miss the overdrive with the LS.

Street driver, not autocross. 

bmw88rider
bmw88rider SuperDork
12/11/17 7:59 p.m.

You look at the build costs and the 5.0L mustang route is the best. The platform is "old school" so the parts are cheap now. It's got more than enough HP to get going. 

 

What kills you cost wise is the mounting kits, transmission, and the wiring if you can't do it yourself. You can do something out of the norm but you have to be able to fab it up otherwise it won't be cheap to do. Those who do the "cheap" swaps have 100's of hours in fab time and build time into them. 

 

I love mine and I paid for it but I knew this, I wasn't going to have the time or skills to finish it right so it was my only path to ownership. 

SVreX
SVreX MegaDork
12/11/17 8:01 p.m.

In reply to bmw88rider :

I am prepared that this may take me a lot of time.  

I am good with wiring, and can probably get through the fab work myself.  If I use the 5.0, I've already got a Monster crossmember. smiley

oldopelguy
oldopelguy UltraDork
12/11/17 8:02 p.m.

Plenty of Camaros came with T5s, and the Solstice came with the MA-5, and they are at least as sporty as Mustangs. The Nissan and Toyota stuff is just as good and an adapter away too.

SVreX
SVreX MegaDork
12/11/17 8:03 p.m.

In reply to bmw88rider :

I love your car.  If I could afford to buy one from FM, no question I would.

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
12/11/17 8:09 p.m.

Find a broken one and fix the broken part.  

Seriously, there are just so many little things involved in shoehorning a V8 into a Miata that even with the donor car you'll have to build or buy a ton of stuff.  For the 5.0 the headers are very custom.  The driveshaft is custom.  The transmission crossmember is custom.  You'll need a ton of radiator to keep it cool.  The 1.8 diff "might" hold up if you don't beat on it.

( MIne took a pounding in the CSP car launching as hard as possible with 275 Hoosiers, generally an axle goes first before the diff)

I really have a hard time imagining building a complete V8 Miata for challenge money (at least with my limited abilities).

 

SVreX
SVreX MegaDork
12/11/17 8:10 p.m.

I think the power level is a big difference for me.

If I go with a 5.0L, I will hit my 300 hp goal, but not much head room.  It would take deep pockets to go much further.

If I do the LS, it would be much easier to get close to 400 hp.  400 is very nice, but I am concerned at that point that the rear end upgrade is a requirement, and the questions regarding the trans compound.

As much as I'd like 400 hp, I really do think I would be very content with 300 hp, and the overall build seems much easier.

My turbo Miata (The Mumpkin) was about 230 hp, and it was a rocket.

SVreX
SVreX MegaDork
12/11/17 8:11 p.m.

In reply to KyAllroad (Jeremy) :

I've looked hard for a broken one, but have not found it.

Want to sell me yours?  cheeky

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
12/11/17 8:14 p.m.

Oh, and the oil pan has to be customized to clear the crossmember in a 5.0.

and in mine, with fuel injection there are three holes cut in the hood to clear various bits.  It really is a tight fit.

Robbie
Robbie PowerDork
12/11/17 9:30 p.m.

Go drive cars with the drivetrains you are considering. Your Miata will feel a whole lot like they do to drive. Do you want a mid eighties mustang? Or a late nineties Camaro? I think you will be disappointed with how either T5 or T56 shifts compared to Miata, but the T5 predates the Miata by a good margin.

Also, factory engineers spend a lot of time on engine and trans combos. Factory engineers do not review Joe shmoe's adapter plate with a pressure plate, clutch disk, and pilot bearing from 3 different makes.

I think you should hold out for the T56 if you want a v8 Miata.

Dusterbd13
Dusterbd13 MegaDork
12/11/17 9:36 p.m.

Im building a 300 horse v6 miata with a t5.

I honestly think 250-300, with proper spring rates and rear gear, in an nb, would be a fantastic dtreet car. Even at 2700 lbs with driver, ac, and no efforts spent on weight reduction, it would be a joy. This is based on 20k in 6 months on a bone stock nb1. 

bmw88rider
bmw88rider SuperDork
12/11/17 9:36 p.m.

What ever you do, make sure you budget for good tires :P

 

If you go the NC route and need any pictures etc, just PM me. I DD her because I'm so confident in her. It makes the commute  lot more fun. 

SVreX
SVreX MegaDork
12/11/17 9:45 p.m.
Robbie said:

Go drive cars with the drivetrains you are considering. Your Miata will feel a whole lot like they do to drive. Do you want a mid eighties mustang? Or a late nineties Camaro? I think you will be disappointed with how either T5 or T56 shifts compared to Miata, but the T5 predates the Miata by a good margin.

Also, factory engineers spend a lot of time on engine and trans combos. Factory engineers do not review Joe shmoe's adapter plate with a pressure plate, clutch disk, and pilot bearing from 3 different makes.

I think you should hold out for the T56 if you want a v8 Miata.

Oooh... Good word.  

 

You just made it harder on me! wink

NOHOME
NOHOME UltimaDork
12/11/17 9:52 p.m.

In reply to SVreX :

My buddy the Minion did one for couch change money and still has fond memories. 302t5 combo with a welded

 up hybrid driveshaft and stock rear suspension and differential. Never did kill it but then again he is not a burnout fiend.  Exhaust was side pipes. It would have been under challenge budget of he did it.

 

I consider the Molvo drivetrain swap to be low budget at $7500 USD for the drivetrain and around 10k all in. That is with everything rebuilt or new and a Fitch EFI. Patriot tight tuck headers fit. Monster Miata rear bits with 8.8 LSD worked out around $1500.

If you can fab, consider a stick rear axle with coil overs and 4 link if it has to be cheap.

 

Buy a running donor car and recoup as much as you can. You can build a beater for 2000 but something nice is going to take challenge shopping skills to hit the  5000 budget

Keith Tanner
Keith Tanner MegaDork
12/11/17 10:03 p.m.

The V8R Spec cars use a 5.3 and a T5. The shifter comes out a bit too far forward and you have to do some tweaks to the trans to make it work - plus there's some very expensive clutch master in there. At the end of the day, I'm not sure how much you'd actually save. 

The Ford engined cars were something else when they were new, but talking to people who have driven both the LS cars definitely move the game on. The packaging is better too - the LS gives more room for the steering rack, front sway bar, hood and ground clearance. The 5.0 can obviously be made to work - it's won the Challenge! - but with the parts you have on hand I'd be looking to put together your existing package.

The rear end holds up to 400 hp turbo Miatas if you don't wheel hop them. A lot less torque, of course, and that 4.1 gear may not be the best choice behind a T56 anyhow. Given the price of used Miata diffs, you could probably swap in an 8.8 without going out of pocket.

Interesting thought - what about a Rover V8? Nowhere near as much power as the LS, but it's all aluminum and would work pretty well with a T5. It's a common British combo. It's a relatively small engine so it might package well and will make the right noises. It's been done a few times, but I don't think it's considered played out in the US.

BTW, if you're interested in a T56 that needs some attention to the reverse shifter fork, drop me a line wink

SVreX
SVreX MegaDork
12/11/17 10:20 p.m.

In reply to Keith Tanner :

The line has been dropped!

DeadSkunk
DeadSkunk UberDork
12/12/17 7:51 a.m.

I have a friend with a 215 Buick in an NA, backed with a T5. It was done without any kits, and it's a tight fit. The Buick/Rover is the same dimensions as the 300 iron Buick, which is to say, slightly larger than a SBC. The upside is that his NA is only 40 pounds heavier than stock and makes the expected rumbly noises.

SVreX
SVreX MegaDork
12/12/17 8:32 a.m.

I don't think I'll be doing a Buick, or a Rover, or any other variation. 

It's gonna be an LS, or a 5.0L.

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