emccalment

Don't act like you're not excited about it.

I've been thinking about this for awhile. I've been looking into the suspension needs of the extra weight, which type of engine is best, and all that fun nonesense. Of course my search led me to the LSx engine, for weight, mpg, ease of power, and cost reasons.

Sooooo, what's the best way to go about the LSx swap? I've been looking at Flyin' Miata kit, but was just curious the other options out there. My mechanical abilities are still in the early willing to do anything myself stage.

And who better to ask than those who've done it before me?

Thoughts?

MRM331

Welcome!

I've built four Ford powered conversions and while the LSx conversions are cool, two of your four reasons for going that route are fairly moot. While you will possibly get better gas milage with the LSx and out-of-the box power will be higher (depening on model) the finished weights of both types of conversions usually come out about the same (around 2700 pounds) and, while LSx prices are dropping, you can still build a Ford conversion fairly cheaper than a LSx.

If I were to do an LSx I would use a combination of the Boss Frog or V8 Roadsters front subframe, a conversion bell housing to run a faily inexpensive T-5, a trans mount from Monster Miata to hold the tail of the T-5 and a Monster Miata 7.5 rear end. I've priced this out, and using this formula I think I could build an LSx for under $16K or so. A full Monster Miata kit Ford can be done for under $12K if you know where to scrounge for parts.

Again welcome!
-Jason

emccalment

Apparently I don't know where to scrounge parts, lol. I've priced a lot of things here and there, and this is what I'm seeing, with a little bit of previous car ownerships sprinkled in.

You can get a LS1 and a 6 speed for like $5k, as a bundle out of another car. It will make 350 hp/lb ft without you having to do anything. Also, because of the newer electronic system, will pull better gas mileage than a 302. My old 302 pulled 20ish on the highway, granted in a significantly heavier car. It's also more expensive to acquire a 6 speed to mate up to a 302. On top of that you have to do a significant amount of work to a stock 302 to even begin to approach the numbers listed by the LS1, and it won't touch the torque curve.

After that I started looking up crate motors, and motor for motor, it looked like the LSxs were actually lighter due to the aluminum block. Buying an aluminum block for a 302? I'll pass, the block costs as much as the crate LSx!

If you can point me in a different direction from that I'd be interested to hear it. My brother is die-hard Ford and wept slightly when I said I was leaning toward an LSx instead of a 302. He tried to reference torque curves and power output at certain RPMs, and all he did was reinforce in my mind that the LS was a better option.

emccalment

I may have also failed to mention that I'm not considering price really in my prospects! I figure if I'm gonna do this, I'll save money where I can, but ultimately I'm going all out. Engine, suspension, brakes, body work, interior work, stereo, other miscellaneous pieces here and there. My other option is I could buy a new BMW for way more money.

fmowry

It helps to know where you live because that certainly can play a part in which way you want to go with the swap. It also helps to know if you want to do an NA or NB (or NC).

For instance, for an NB, (or late NA for that matter), if you live in an OBDII emissions testing state, there are probably rules for swapping a like vehicle type (think car into car, not truck into car) motor of equal or newer model year into the recipient car. So you can't put a 5.0 from a '93 GT into your '96 Miata.

Also, many states do have historic tag possibilities. Early NAs can qualify for this in which case you may get away with a swap that is less scrutinized, or not scrutinized at all by the smog police.

emccalment

Tennessee area, about an hour outside of Nashville. And uh... that one post, I'm an idiot. It occured to me on the way back to my room that I used 350 and LSx interchangable. My truck has a 350 and all my chevy friends used to be big on them. Got brain tied and didn't click it right.

I don't know that they do emissions testing in my area. I grew up in Indiana and we never did them. Then I moved to Arizona for awhile and they didn't do them there. I got my motorcycle transfered to TN, but nothing else, so I'm not sure. And I'd be looking at a 94 and up NA.

I could probably register the car in Indiana worst case scenario.

emccalment

I probably should have checked prior to the last post, but my county does not require emissions testing.

MRM331

I have been accused of being a little "Ford-Centic" in the past. My father brought me up to bleed Ford blue and that sadly is the consequence.
When I first got into this game about 6 years ago the only kit option was the Monster Miata kit for the Ford 302. A few folks had done old-school Chevy small blocks by that point but it required a lot of fabrication. The main alternative to the Ford was, believe it or not, the Rover/Buick aluminum V8!

Flash forward to now when we have two very-well designed kits for the LSx to choose from. The LSx is a great engine. I will admit that it is superior to the good old Ford 302 in many ways. It is more modern, it can make better fuel economy, the engine itself is lighter, and it has more power out of the box. That all said, it cost more. I still think, for me at least, that the cost of an LSx over a Ford does not justify the advantages. Here's where I'm coming from:

Ford Build:
-Donor 1990-1995 (OBDI) Miata in good shape: $3000
-Conversion kit parts: $4000
-Harness: $225
-A9L computer: $100
-Driveshaft (aluminum-from me...): $400
-Engine (from an Explorer-gets you GT-40 heads and intake, modern starter): $200
-Used Mustang cam: $35
-Mustang accessories (used-AC compressor, alternator, front cover, brackets): $100
-Mustang Bell Housing (used): $50
-Mustang T-5 Trans (used): $300
-Thunderbird 7.5 diff with limited slip with half shafts (used): $100
-Custom Exhaust: $1000
-Other stuff: $1000

Total (estimate): $10,300

I left off upgrades to the chassis (rollbar), suspention (coilovers) and wheels/tires (225 on 8 inch rims minimum) since those are areas that need upgraded regardless of which engine you go with.

The above will get you a nicely balanced car that will make about 240 to 250 rwhp and about 300 foot pounds of torque. A set of aluminum heads for about $1300 and a better cam for $100 can get you up to 290 or so rwhp without any tuning needed. A 331 bottom end (add another grand) will get you over 300 rwhp (maybe up to 350) but at that point you're going to need a custom tune for another $500 or so.

I think you’re looking at this from the perspective of using a T-56 and an aluminum Ford block which does make the price higher than a LSx. Like I said, all street builds seem to come out around 2700 pounds or so, mostly because the T-56 used in LSx builds far outweighs the T-5’s used in Ford builds. Cutting down the weight of a Ford block by using aluminum is really not worth the price.

Ether way you go we’ve all glad to welcome another to the fold. If you do go the LSx route do look into the Monster Miata 7.5 diff option though. It can save you a bit of money and make it easier to route a true dual exhaust.

Good luck with your build and welcome,
-Jason

emccalment

I understand the tendancy toward Ford. My brother's a huge ford guy, and so was my uncle. I'm more about impracticality and craziness, lol. Back when I was first looking into this all there was out there was the 302 swap as well. The 302 is also the only engine I have any real wrench time on, it holds a special place in my heart.

I'm all about things that make anything easier.

As for the Boss Frog vs. FM (Am I missing any others for LSx?) It looked like the Boss Frog required less sheet metal work but changes the location of the sway bar up front. I'm not so sure that's a good idea, as I assume that would change the entire handling dynamics of the vehicle?