Hello all, I am a newbie who has been infatuated with this idea since I watched the Banshee build on Gearz (5 times...).

So forgive me, I don't know much. The first and last engine swap I did was the installation of a Chevy 350 into a CJ-8 and that was done in the time before time. But like most red blooded Americans I've fantasized over Shelby's Cobra since I can remember. It's been on my bucket list since...well then. But I can't justify the absolute financial impractically of it. The Gearz Banshee really changed that for me.

I want a drivable street machine. I don't necessarily want to make it my daily driver, but I'd like it to be an option. So, I'm looking for a compromise. I want a machine that will bring a smile to my face to drive but gets better gas milage better then a Hummer H1.

Is there such a drivetrain compromise? Before a Chevy/Ford debate breaks out, I should say I'm leaning towards Ford on this one. Is 300+ hp possible while getting something closer to 20 mpg then 10? Or is this just unrealistic?

Thanks!

PS If its not possible, then I might just have to go radical, MPG be damn.

 

My mileage was 18 city and 22 hwy with 270 hp injected 5.0 3.27 rear and .60 5th gear . Hwy speed was between 70 and 75.

 

Welcome to the forum! You are on the right track for sure by doing your homework before you start. I watched those Gearz videos many times and read everything I could for over a year before I started and I still had a bunch of surprises.

I would think the Miata being so much lighter than any donor car would get at least as good of mileage as the car the drive train came from. I had no problem getting 25mpg on the hwy with my 02 Camaro SS donor car. If things go as planned I will be able to give you the Miata numbers in a couple of weeks!

 

Two of us in my area have 5.0 swaps, t5z transmissions, and 3.27 rear ends. My buddy built his engine with upgraded heads, cam, and intake, and it supposedly is at around 300 hp. He gets upper teens in town (though driveability is a little rough) and around 25 on the highway.

I, on the other hand, have a bone stock 95 SN95 engine, heads have never been off. Came from the factory with 215 hp and 285 torque. I have a mpquino on it. If I granny-drive it in town, it gets 20 or better. If I race from stoplight to stoplight it gets 16-17. On the highway, it gets 23.5 to a little over 26 depending on outside temp, whether top is up or down, and whether the ac is on or not.

 

I just restored an 89 560SL that has similar numbers on hp and torque, but gets around 17 mpg no matter how I drive it. It weighs 3700 lbs though. They don't call it the Panzerwagen for nothing.

I'm torn. Part wants to go all out mpg be damned, but the practical sides looks at almost $4.00 per gallon gas and thinks otherwise. That side can be a cheap bastard.

 

You mentioned wanting a Shelby Cobra but do you realize it takes very little to exceed the performance of the Cobra with a Miata? An NA with a 2000 or newer LS1 or LS2 warmed up with a cam and tune has a better power to weight ratio than a 427 Cobra. The Miata also has better brakes and much better suspension. Oh and the Cobra got 9 to 12 MPG and you would be hard pressed to get that bad of mileage even going all out.

In my world stuffing a big V8 into a Miata is pretty radical and pretty much going all out. But what does going all out mean to you and why do you want to do it? Are you going to track the car or something that you need huge HP? Who do you want to beat with it?

 

I have a 331 Ford running on a Megasquirt 2. With the last set of tweeks I made to the tune I was able to get it up to 22 highway, 15 city and 11 on track. Proper tuning is everything.

Go with the Ford. You can get into it for a lot less and the build is a lot easier. If you have any doubts as to its performance watch this vid I just shot:


I was driving it at about 8/10ths. The guy in the Vette at the end who passed me (after 10 or so laps) has a bit more track experience and was driving 9/10ths.

The car has between 360 and 400 crank horsepower, a full interior, power steering, a stereo, and AC and I drive it to work at least 3 out of 5 days of the week

-Jason

 

At this point I'm not sure what I want...

As to why? I suppose Mallery answered that best, "...because it's there". smartass joking aside, I'm really just learning at this point. I probably wouldn't be able to start any major project until January at the earliest, so I'm in what you might say is the pre-planning phase. I hope to learn a lot from you good gentlemen.

 

OMG ...I think I just spotted. That was AWESOME!

How much money will that cost me. (I wonder how much I can get for one of my kids...). Yes, I very much want that.

 

Jasons car in the video is for sure not an all out build. It is a smartly built daily driver with a few tweaks to work well on the track. Cost to build that greatly depends on your level of involvement and fabrication skills.

If cost is the biggest issue for you then you need to buy an already built car. And there is a couple of sweet ones for sale right now at very reasonable prices. If you want to spend a little more for it to be your build then figure about $15,000 to build something like Jasons car. You can cut some if you are capable of fabricating your own frame and add some if you want to go with better parts like aluminum heads. I'm a little over 16,000 with my LS build at the moment and my car is about the same level as Jasons.

For what it is worth I have found over the years that everything you do to make the car work well on the track also makes it more fun to drive to work. However there is a limit and spec miata suspension is not date car stuff!

 

Oh, I enjoy building, so...

As far as fabricating my own frame, I'll be using Monster Miata's kit so some cutting, and light welding is all I'll have to do as far as frame modification, right? I do want to make look good.

I'm not sure about actual body modification yet...jury is still out there. I'm also not sure about what budget I'll spend, yet. I'm starting to casually put together a project ------sheet. Once I settle on my ultimate desire "dream machine" plan, I'll probably work back from there.

Thanks for the advice!

 

I am getting between 11 & 13mpg, & I change rear tires & oil every 3000 miles.

 

Sounds like you have landed on doing a Ford and there are is no question the 302 is a mighty fine power plant for the car. Yes Martians kit is the least invasive with very little cutting and welding.

My original plan was to go Ford too but figured out if you build a ford to the same specs as an LS the cost is about the same. (347 stroker, aluminum heads, T5z trans etc) That and when I got to really thinking about it I decided an extra weekends worth of work to mod the fire wall was a terrible reason to choose one kit over another. In the grand scheme of things 15 hours worth of work one way or the other in a probably once in a life time project means nothing. Oh and it also helped that I happen to already own a Camaro for a donor car... But the Ford is a great choice because they sound better, fit better, are easier to build and if you don't push the engine too hard, they can cheaper to build.

Have you seen the project sheet in my blog? The link is in the right hand column and I do keep it updated. https://skydrive.live.com/view.aspx?...EnMKcJ0CspHsIw It is an LS sheet but offers good insight on how the little things you don't think about really add up. If you want to PM me your email address I'll send you the estimate I wrote up to do a Ford too.

 

LOL!

 

I only get around 12mpg in the city/17-18mpg highway despite trying to tune it better, but I have a carb, and a cam that I think is partial to blame.

 

I get 15 in the city and about 20 mpg on short highway trips. I suspect on a long highway trip I would probably get at least 22mpg. 5.0 with cobra intake, 24 lb injectors, AFR heads, trick flo stage one cam.

 

I am impressed with your management of that project, very nice! Thank you for sharing.

 

Jason, you need a pair of Jon Kasee P-38 heads to kill that 'Vette. I've been trying to communicate as much as possible with Kasse but they are extremely busy. The guy cherishes a national renown reputation and attends many racing events; he's in high demand with limited time. They're trying to come up with an EFI camshaft grind to optimize the Miata/Ford application; I hope that they come through for me.

QVOX, someone can get wrapped up investing money in these projects; it feels good when you come up with a design of your own that embarrasses some of the best muscle cars purchased off a showroom floor at an extreme cost. If more youths got involved in engineering their own performance cars, then maybe we would not be looking oversea for engineers. Lots of home grown gear-heads later on end up working for the auto makers and etc.. As pointed out above, take time to carefully plan your project out, leave yourself some room to improve later on as your budget can increase, and most of all, don't wait too long as you may lose interest. Keep a schedule with goals to meet; I have run into some health issue myself and it really took the wind out of my sail advancing my goals, but since I'm retired it frees up some time to maybe catch up. Oh, one more advise if I may, if you're not going to enjoy the challenge and have fun doing it, then don't even start, and as suggested above, just buy an already completed ride.

My 2 cents!

 

New to this forum, known over at the Engine Conversion forum. I've got a '99 Miata, stock LS1, T56, and 3.23 LSD diff. Running on normal 205/50/15 tires I get about 21 mpg around town, 27-28 on the hwy. Haven't got my baby on a chassis dyno yet, but my stock LS1/T56/3.42 C5 pulls about 315 to the wheels.

HTH, and have a good one,
Mike

 

Impressive...

If it dynos out as you expect, I'd say you've achieved an excellent balance of power and practicality.

 

If you have tuning software, can lean out normal street/highway driving to 17:1 AFR. We have done just that. Only time we checked fuel mileage was while traveling to Hot Rod power tour event in Michigan in 2011. We got 29+ MPG freeway. Never tested city mileage. LS1 11.5:1 SCR, fairly agressive cam, 3.90:1 rear end, 25.1" diameter rear tires.
Engine dynoed 523 HP in 2003. Who knows how much is left, probably close to that number. We take care of the engine seasonally, checking valve springs, rocker arms, pushrods, valve stem seals, check oil filter for metal flakes. Run test logs as needed when an engine related tuning issue occurs. GM Viper spec T56. Most freeway driving done in 6th gear.

 

Now those numbers are truly inspirational. Well done sir, well done.

 

Clarified that for you. I figure I'd scatter mine everywhere!

 

Understood. It's actually pretty simple & safe. WOT fueling runs from a completely different table (PE fueling). So, there's no risk of running lean @ WOT or high load. Agreed though, that it's best for a person to have a good understanding of what's happening within the tune before making such a change.

 

I ran 425 miles over the weekend on mine. (LS1 with cam, tune, 3:55 gears and the exhaust cork in) We did 200 miles on hilly twisty roads with epic views and even better 40 mph corners. I spotted a 427 Cobra and as tempting as it was I respected the legend and did not pass him. Did about 25 miles in stop and go down town traffic and the other 200 miles was at 80 on the freeway coming home. I got 24.8 mpg for the trip and was delighted with that.