Purchased my first Miata this summer, been working at it a bit.

- Replaced soft top
- Upgraded to LED headlights
- cleaned up the interior
- other minor mechanical servicing.

Pros and Cons of a V6 vs V8
Been looking for sometime at the V8 conversion but I'm on the wall a bit. Don't get me wrong V8 power would be awesome, but I'm thinking it maybe a bit much for me. I'm thinking of maybe a V6 but I wanted to hear from the V8 folks. Is it worth trying to put a Ford V6 into these cars, or has it been tried and failed? I know with the V8 there are a lot of parts and support for them, hence why I'm on the fence about both.

Thank you all for your comments and I look forward to reading your opinions on the matter.

 

Welcome to the forum!

 

Go with a stock 5.0 & forget about the V6. There is a kit for the Ford that is a proven winner. The V6 would involve some fabrication. The stock 5.0 can be upgraded after you realize what you have been missing. Welcome!

 

tbone is spot on and to expand on what he said with a V6 you have to fabricate EVERTHING to make it work. Building an engine cradle is no small thing because the front suspension also bolts to it so it has to be strong and pick up points and A arm mounts have to be spot on. You have to build a trans mount and deal with a million other things you don't know going in and will have no one to help you with.

Which engines are too tall for the car?
Which engines have a rear sump oil pan?
What engines put the shifter in the right spot?
What V engine (if any) will clear the steering rod without 4 digit custom headers?
Will the oil pan clear the steering rack?
Will the Miata clutch hydraulics be large enough for the v6 clutch?
Will the engine power steering pump work with the rack?
What do I have to do to make the tach and speedo work with the V6 computer?
What about the rest of the gauges?
God be with you if you try to use a drive by wire engine...
Will the stock fuel pump be enough or do I need to go bigger?
Will the exhaust manifolds clear the frame rails or do I have to have custom headers made?
How much bigger does the radiator need to be?
What spring rates do I need to support the extra weight?
and on and on it goes...

All those questions and 100 others you don't even know to ask till you open it up are known by guys here that have built V8 cars and there is kit parts available to resolve them.

Last but not least the conversion process itself and all the parts you have to rework or deal with is exactly the same for a V8 and a V6. Wiring, exhaust, rear end, cooling all have to be handled and modified some how for both set ups. And the V6 pay off? 10 times more fabrication work for half the power and probably more cost than using a kit.

A stock 5.0 is 225 hp. If you really want less HP than that do a turbo on the engine that is in the car. For what it's worth I've looked at a number of V6s thinking 300 hp was enough. And for 99% of my driving it's twice what is needed. But on a pay day Friday when the sun is out and the girls look fine there is nothing better than hitting the key and hearing 450 ponies come to life. I may only use all 450hp for a few seconds a month but for those seconds the effort and cost is worth every penny!

One finial thought. The notion that a V8 might be too much for you is precisely why I think you should do a V8. I drive mine every day and there is an element of intrigue and suspense in knowing this car could just as easily kill me as get me to work. Even though I have only done it once just knowing what if I bang into 4th a little too hard at 95 mph the back end will break loose puts a smile on my face every time I drive it.

 

to me even if you were fabricating everything from scratch on either v6 or v8, why do the same amount of work and money for a v6 vs v8...

i took mine out for a first spin yesterday, and the sound of this v8 with the torque is absolutely breathtaking, and it's bone stock! yet insanely exciting!!

i say v8! lol

 

Congrats on that. How did you reroute your fuel?

 

ran new lines from under the car up into the tunnel, and through the corners that get modified on the firewall.. straight up into the engine bay... i'll post pictures on that original post today

 

Thank you all for your feedback. As for fabrication, I don't believe it would be a lot since I was planning on using a V6 from a mustang so it should fit right into the same spot as the V8 for those cars. But at last, I just needed to hear the go V8 from some what normal minds. I sure hope Martin is still up and running. As for the V8, I was planning on going with a crate motor from Ford so that I had the reliability, as well a brand new tranny and rear end. If I'm going to spend the money I wanted to know this car will last for years of enjoyment.

 

So you are thinking you could use Martins kit for a V6? Not a chance. The engine cradle and all the mounts are completely different from a V6 to a V8 Mustang in the years most guys use. The wiring too is completely different. It would be 10 times more work and cost than putting a turbo on the engine you have now and that V6 is a dog that deliver no better performance.

I'm not following the logic on buying all new for reliability and would like to understand that better. It seems to me that your car would sit half the year like mine and I have yet to put 7500 miles a year on it even with my 70 commute. My winter beater has 260,000 miles on it and it's nothing for a modern engine to go 150,000 miles with no issues at all. I can't see that buying new would last any more seasons or be more reliable than rebuilt or low mile used stuff would. The other thing I am not following is it seems to me that the biggest advantage to the 5.0 build is donor cars are cheap and by going new you nullify that. I guess to me if I was going to spend 10 grand on a drive train I sure wouldn't use a 90s 5.0.

Mike have you considered an LFX build at all? If you want new and are leaning toward a V6 anyway that might just be the ticket for you. The LFX drive train is found in the 2012 or newer V6 Camaro. It is a 300 hp all aluminum V6 with a 6 speed trans behind it. They make a lot more v6 cars than v8s so it's easy to find low mile wrecks for donor cars and they are much cheaper than V8s are. Don't need to buy headers either since the manifolds are part of the heads. I have not crunched any numbers but my hunch is you could build an LFX car with less than 20000 miles on the donor for a lot less than buying a new crate 5.0 set up and probably have a better running car that fits your needs better too.

V8 roadsters is developing a LFX kit now that should be done shortly but even if it's not ready when you are you could just get a blank V8R subframe and set it up for the LFX pretty easy. The trans mount and rearend would be the same as the LS V8 cars and wiring should be about the same as LS builds too. Just a thought.

 

7,500 miles. I do No less than 1,000 per week and drive it from March until October. Ford sells new crate motor 302 - T5 - and rear diffs, 8.8 I believe is the number or 8.1 Up in my area donor cars usually have some bad history

 

WOW that is some serious miles for sure! Another diff option is Martin offers one with his kit for about 1000 bucks extra.

 

I just noticed that, will need to talk to him about it

 

I have Martins full diff and axle package sitting here if you ever need pics of anything. Will be about another month before it goes in.

 

Great more interested in the ease of install and performance,

 

I need to say, I'm sure enjoying this forum a lot more than another I was just on. At least here I can ask simple questions and get creative feedback and not trolling comments. Thanks for putting me back on the right track with the V8, looking forward to the build since this is my first Miata. Current budget is $15K with a $5k wiggle room. I hope I can pull it off. $5k is going towards my garage shop first. Car lift and new roll-up-doors.

 

NICE - i went into this with 8000$ budjet, and a 2000$ cusion lol... a little crazy i was..

I think i'm up between 12k and 13k with all the small stuff.. keep in mind i also bought a used 5.0/clutch/bell/trans/all accesories/harness/computer for 1500$, and a used 8.8 diff at the junk yard for 200$.. built the exhaust myself, kept the stock sway bar...

still it's costing me close to 13k in the end

The monster kit cost me 6400$ by the time I added power steering and a driveshaft, had Martin provide a used k-member/hubs/pan which was cheapper than shipping mine accross the border, paid for the extra shipping accross the border, paid the annoying brokerage fees, and paid the difference in exchange rate at about .90c on the us dollar..


But ya, this is a great comunity, people tend to respect other's opinions.. i have rarely/never seen pointless caps lock screeming matches on the forums here...

 

There has been a few but I try to say off the forum when I forget to take my meds.

Budgets are super easy to work out for these builds. Spend a couple of hours going over build threads to figure out all the parts you need that are not in the kit. Then search the net to figure out the cost of those parts, add in the kit price and multiply times 1.75. I wish I was kidding but I have seen it over and over that is really about right to figure the cost.

Interestingly enough you can use the same process and the same formula to figure out how long it will take to build and it too is accurate. Like that ever stopped anyone though...

 

Neverthought of the shipping cost, might be cheaper to do all the body work up here, including V8 prep work, and have the drive train shipped directly to Martin. schedule a date and drive down to get it installed. Could just incorporate this into a family vacation.

 

I'm not quite understanding your idea... are you saying you would get martin's shop to install parts of the kit?




I think for me, deep down i knew this was the case, but I chose to be naive because I really wanted to do this.

 

See there in lies the intangible that you can't factor in. The challenge, interest and yes the fun of the build. Building something that is uniquely your own, pushing the limits of what you ever though you could do and the satisfaction of a significant accomplishment goes along way to make up for that .75 percent overrun. But then you said it way better than I could have....
For me the first drive was sort of anticlimactic because I was so terrified of fire and things falling off. But my hands were shaking from being so excited when I hung up the phone from putting insurance on it. I think it's about as close as a man can come to experiencing what it's like to have a baby.

And I never dreamed that after driving it for a couple of weeks I'd kind of miss being in the garage working on it. There truly is joy in the journey to build one of these cars that has a value to it.

 

Have the chance to purchase a 302 V8 from a 1990 Crown Vic. Will this motor work on the MM kit?

 

Google says you would spend 10 grand to gain 30 HP which would have to be the most expensive $$ per HP mod ever done to a car. It's rated at 150 hp at 3200 rpm and a whopping 270 ft lbs of tq. Damn good motor to move a bus but terrible choice for a 2400 lb car.

What happened to using a crate motor to be reliable?

 

At a $300 price tag I needed to check, but thanks for the information. Been thinking of some of the feedback you guys have given around rebuilt engines, a crate motor would be great, but I need to keep my mind open to possible local rebuilds. Money saved can go towards everything else for the car. I want the car to feel and look completely new. Some plastic panels are reaching a $400+ price, so I need to keep all options open.

Today after working on the car and trying to do what I can to keep it going until fall, I decided enough was enough, I cleaned up the shop and started moving everything I don't need in there to the shed. Car gets pulled in tomorrow and the teardown begins. Will start the build post tomorrow night.

 

Ah the world is about to become a better place... I'm excited for you this is a really special time in the build.

I don't know the details of the Ford stuff but you should do some more research because that crown vic motor might be alright with a cam in it. If you post the question in the main section you will get guys that know to respond. I know people have used explorer and tbird engines in them but as I understand it Mustang is the best.

Not to throw cold water on you but I want to caution you that the first and most important step in the build is not the tear down it's the plan. I assume you have read the stickies in the general questions section but if not you should go over them as you get going. Actually Jasons is very detailed on the engines that will work and may address the crown vic engine. Anyway my point is I would not want to pull the engine from the car unless I had most of the stuff going back in. If for no other reason that the hunt could get long and you forget how things go back together. But that's just me and every one approaches this a little different. I'm just excited you are taking the plunge!

 

Thanks for the advice, yeah been doing some crazy reading each night, had to start limiting myself to 2 hours, got up on night to grab a drink and it was 5:AM. Not a lot will be done except removing the soft top and putting it away in safe storage since it was brand new. As well other items that I want to make sure don't get damaged. I'm currently waiting on the call about my car lift so once that gets here and installed and big work starts. The plan is still a work in progress but since summer is almost over and I my only real time to work on the car is the weekends I imagine teardown will take me into October.

From what I've read I'm I correct on this plan

1. Fix any rust, issues to main body.
2. Prep body for V8 install
3. Install Drivetrain and do whatever other body work is required for the fit.
4. Teardown the drivetrain again, and start final bodywork.
5. Complete bodywork and reinstall drivetrain
6. Complete Interior
7. ENJOY!