Can we talk about V8 Miatas/ RX7's again?

Yeah, I know this has been discussed. But babble is good for the soul...

I want a V8 sports car that corners like on rails, at a Challenge price. I love simple and reliable more than anything, and want a ton of NA torque kick in the pants. Willing to do turbo later, but not now. I'd like 300 hp NA with potential of 400 boosted. Must be easy to Megasquirt. I care more about cornering than straight line, but still want deep 12's or better. This will be a nicely done street driver- full custom interior. I have never done a V8 swap, nor built an engine. I don't weld (much). I want to build something others will appreciate (and have resale value when it is done).

I am comparing the Miata to the RX7, and several motors. I have been considering the 1UZ-FE, an LS, and a 5.0L.

I already know Miatas. I have 3. That's a big plus. I know how to make a Miata corner. I'm probably gonna blow the rear end. A nicely done LS version has great resale, a raggedy UZ or scavenged 5.0 not so much. I am a little bored with Miatas, but love driving them.

The Rex is better looking (yeah, that matters to me), but older. It has more straight line potential, and more space for the swap, especially the trans. Much more space for tires and wheels. Older design and engineering. I don't know them well. Never driven one.

I prefer hardtops and hatchbacks, but my wife likes ragtops (which matters). I want a manual, but am willing to build it with an auto for the Challenge, then swap later.

I have a nearly free NA Miata sitting here ready for an engine swap.

I have a nearly complete RX7 FC 4.8L LS project (assembly required) available for Challenge money with a TH400 and plenty of go fast goodies.

The UZ has great reliability, VG power out of the box, excellent boost potential, but not many transmission options. Not much after market support. It's also a little weird choice.

The LS is, well... an LS. Excellent choice, and good after market. Prices are climbing on the aluminum versions and various options. T56 trans are getting pricey.

The 5.0L is probably the cheapest, but I am not a Ford fan, and not sure about my power and reliability goals.

Talk to me... WWGRM do?

Any of the truck LSXs (4.8L would probably work best, as the lower torque would be okay in a light car and 4.8Ls are the unloved stepchild) with a well setup auto trasn. With a light car and V8 torque, a stick shift really isn't a necessity, and once again, auto transmissions are cheap. A friend of mine got a TH350 with fresh internals and a shift kit, plus a higher-stall converter for $350.

i'd 4.8/5.3 whatever it is. they're already 300hp n/a, more with proper headers. the 5.3 in my impala is around 340(calculated via quarter mile time/weight) with the only changes being an ls1 intake manifold and ls1 camaro long tube headers. cam gets you 400 without boost. IMHO this would be a swap where the infinitely tunable gm computer is easier than megasquirt unless you're dead set on MS.

the best thing, besides being an LS, is GM lego style interchangeable parts. you want a 4 speed? you get a 4 speed. 5 speed? sure. 6? yup. auto? no problem.

i have a feeling i'll be 5.3 swapping something else here shortly.

V-8s aren't the only way to get to 300 hp these days. Open up your thinking to some of the hot V-6s available these days and you may find it's easier to shoehorn into a small engine bay.

The devil you know is the Miata. With an adapter plate of some sort you can bolt a 300 hp Honda J mill right up to the factory 5 speed and it should move along pretty briskly.

Didn't realize a GM computer was tunable- how does that work?

I think I kind of like the 4.8L. Revs better, and I can afford to loose a little torque in a 2200 lb package. A cam should be all I need to get me the power I am looking for. But, if I go LS, I will probably take what I can get (unless I buy the RX7 package).

Anyone voting Ford?

In reply to KyAllroad:

I like the way you think...

I don't speak Honda. Explain the Honda alphabet soup- What is a J mill, and what is it in? What is it's weight? Stock hp/ tq? NA potential?

It depends on your initial budget. If you have a good budget, go with the LS engines, there's a reason that Chevy engines are the go to engine swap choice over the Ford engines. I think it's mostly the power advantages they have over the Ford V8s, people don't often say that the Fords have engine reliability problems. Of course, the resale value will be E36 M3 either way, so I wouldn't really count on people giving you good coin when you want to sell it. I would also say that you shouldn't worry about what other people think that much. If you do a well put together 1UZ-FE swap and no one appreciates it, too bad for them. Looking back, I probably should have went with a FC RX-7 and did an engine swap later over buying an E36.

In reply to Mr_Clutch42:

Initial budget will be the Challenge- $20XX. But I am trying to not cobble together another scrapped up POS. Willing to put a lot of labor in.

SVreX wrote: In reply to KyAllroad: I like the way you think... I don't speak Honda. Explain the Honda alphabet soup- What is a J mill, and what is it in? What is it's weight? Stock hp/ tq? NA potential?

J is the new series V6 in everything from TLs to TSXs to Odysseys to Ridgelines to Accords to Saturn Vues. Literally just about everything. Displacements are 3.0L, 3.2L, 3.5L and 3.7L. They have horsepower from the 240hp-300hp range and similar torque. Supposedly pretty receptive to NA mods, like headers and cold-air intakes.

What year RX7?

If you are thinking FC (86 to 92) there is little hope for 2200#. My Chump racecar is 2450 (granted, it has a cage) but that is with the rotary stripped down.

I would think more like 2600# for a V8 FC IF you pay attention to weight of the engine and accessories.

I was thinking of doing this myself. I was leaning towards the 5.0 SBF because they are cheap and have a trans that will pretty much hold up.

The go fast parts are cheap too.

SVreX wrote: Didn't realize a GM computer was tunable- how does that work? I think I kind of like the 4.8L. Revs better, and I can afford to loose a little torque in a 2200 lb package. A cam should be all I need to get me the power I am looking for. But, if I go LS, I will probably take what I can get (unless I buy the RX7 package). Anyone voting Ford?

GM computers are actually really easy to tune, especially with HP Tuners which lets you fiddle with nearly every parameter of the ECU. Some truck ECUs do come with hard rev limiters that you can't disable. Come across that before. Supposedly set the rev limiter to 8800rpm, and the ECU showed it set as that, but it would get to 6000rpm and hit a limiter (No, it was not valve float, it was a genuine rev limiter)

I say nay to the Ford 302. 302 blocks have a tendency to hing past 400hp. Plus they only have 2-bolt mains. And distributors. And they are now all over 20 years old.

In reply to Mr_Clutch42:

Regarding what other people think... there's a really big part of me that doesn't give a flip.

However, I have built a Challenge car every year since 2004, and I have ended up with a really big pile of crappy old cars that have no life after the Challenge. Don't want to do it again.

I am not worried about what people think. I am wanting to build something I can drive on the street that others will appreciate as well.

In reply to SVreX: He's refering to the Honda J series V6 engines. Early 00s Accord versions (J30A4) have around 240hp, newer V6s have around 271 hp, from the Accord, Acura TSX, RDX, etc. (J35Z2, J35Z6). Not sure of the weight, but they are all aluminum, so they are almost guaranteed to be lighter than any V8 you want to swap in.

wvumtnbkr wrote: What year RX7? If you are thinking FC (86 to 92) there is little hope for 2200#. My Chump racecar is 2450 (granted, it has a cage) but that is with the rotary stripped down. I would think more like 2600# for a V8 FC *IF* you pay attention to weight of the engine and accessories. I was thinking of doing this myself. I was leaning towards the 5.0 SBF because they are cheap and have a trans that will pretty much hold up. The go fast parts are cheap too.

I am thinking FC.

I know 2200 is optimistic, but I am very good at managing weight. The Mumpkin weighs 1850 lbs, and my original SVX was 1000 lbs under stock.

It's a goal. If it hit 2600, it wouldn't hurt my feelings (as long as I have the hp on tap).

Read this blog for a grassroots approach to the Miata conversion.

http://miatav8.blogspot.ca/2014/01/rear-subframe.html

Some observations from my ongoing experience:

The rear end and axles are expensive. There are some work-arounds using Factory five axles and broached Miata hubs (Covered in Mikes blog), but I gave up and went Monster Miata route. Double Ouch with the Canadian dollar.

LSx is a reasonable path until you have to buy a gearbox or rebuild the engine, then it gets expensive. If my project was not what it is, I would have gone LSx.

The whole game gets expensive once you start to rebuild every system on the car to cope with the new warhead. Cause you might as well do the coil-overs, and the bushings and the bearings and the brakes and.....

If you care about resale, you should consider going with one of the Branded conversion kits like V8 Roadsters or Monster Miata. Don't know if Vorshlag ever released their kit, but I like what I was seeing.

I would not recommend going into a DIY Miata V8 conversion without 15k in the war-chest.

uh, if you pass on this FC 4.8 with TH400 that is almost done please let me know.

Honda J = the v6 that comes in odysseys, ridgelines, pilots, accords, and almost all Acura offerings. 255-300 HP in stock form, plenty of torque to make my 05 odyssey move out. biggest issue is it never came with a factory RWD trans. There is an adapter to the miata manual trans that I know of, but I don't know of any other RWD options for it.

I really think the answer to your question is FC + LS. Basically the FC gives you the looks, differential, hardtop, (brakes and handling easily upgraded), and the LS gives you power. both are quite cheap if you are willing to go auto on the LS.

I think either an LS powered FC or a c4 vette have the best capability for winning the challenge (or at least beating all the non-trailered cars) with a full interior. Remember the vorshlag e30? I think FC > e30 anymore when it comes to value, and the auto trans will save you cost and increase your performance.

In reply to Mr_Clutch42:

Thanks.

The hp is there, but V8's are cool!

(Not sure too many people would notice Flyin Miata is they built V6 Miatas with Honda engines).

I am flexible.

Robbie wrote: biggest issue is it never came with a factory RWD trans. There is an adapter to the miata manual trans that I know of, but I don't know of any other RWD options for it.

They have also been swapped into S2000s, although I'm not sure about the details.

J-series, with engine, intake, accessories, exhaust manifolds, axles and transaxle weigh in at 550-575.

Lots of OBDII computers can be tuned/reprogrammed with proper software. Some of it is open source, some of it is handled through aftermarket dealers or companies like Diablosport, SCT, Cobb, Trifecta etc. The general process is you buy a device that holds a file (either written by a pro, or by you through open source stuff) then you plug it into the OBDII port and upload your "tune" to the factory computer.

In reply to NickD: Would they get decent fuel mileage in a FC? It might be a good option for me if I wanted to get a FC.

Edit: I would be better off going with a J35 over a 5.0 Ford.

NOHOME wrote: I would not recommend going into a DIY Miata V8 conversion without 15k in the war-chest.

Ever built a Challenge car??

In reply to NOHOME:

Good link, and good word on the branded conversion kits.

Not gonna do it (for budget reasons), but your logic is very sound.

I've had 5.3, 5.7 and 6.2. I don't miss the 5.3. The 5.7 is a much stronger motor than the 5.3 - stronger in power and torque, I'm not referring to physical strength. The 5.3 was just weedy. Some of that was due to the cam, but it didn't have the top end to justify the lack of bottom end. The 5.7 stomped it right across the whole rev range. The 6.2 is in a different class. When I replaced the 5.3 with the 6.2, my top speed at High Plains Raceway went up by something like 15 mph.

SVreX, in your case I'd be tempted to go with the RX7 4.8 project car. It's got your hatch already and (I believe) a stronger rear that may take the V8. It'll be the budget choice, and that 4.8 is apparently a boost monster. It's certainly viewed as one due to the Car Craft test. If you didn't have that option, I'd be voting Ford for the budgetary factor.

The LS Miatas are awesome beasts but hard to build on a Challenge budget without cutting a lot of corners. And those cut corners are going to affect resale. Heck, any Challenge car is going to be hard to get to a decent resale.

It's worth noting that the FM-built LS cars have demonstrated significantly better resale value than those from other pro builders. I think this is due to sweating the details.

SVreX wrote: I have a nearly complete RX7 FC 4.8L LS project (assembly required) available for Challenge money with a TH400 and plenty of go fast goodies.

Assuming this package is the one I know of, I'd vote you go this route. I'd love to see that thing get built, as the potential is scary (in a good way!).

Having owned 2 different V8 FCs, I would suggest that route. A V8 Miata would certainly be a fun car, and Keith's Targa car proves it can be a real race car, but I'd prefer the space and layout of a V8 FC over a Miata. Plus, if you're wife likes ragtops, keep one of the Miatas around for her to drive. Then you get your fast hatchback/hard top.

As for the 4.8, this link gets passed around a lot, but is highly relevant. 1,203 HP from a stock 4.8L!

Hot Rod - Big Bang Theory

In reply to Keith Tanner:

Thanks.

It's not actually resale (cause I don't intend to sell), it's a measure for me of building quality.

Challenge cars are a compromise. Anyone can see that when I parked my Miata next to yours in the corral.

But I have gotten pretty good at this game, and believe I am ready to hold myself to a higher standard. Most of the quality issues can be addressed with more time and care- except, of course, name brand parts.