BGordon

Since my current Miata V8 swap is 99% done and I really loved the process of doing the swap my brain is going in the direction of planning my next Miata swap.
For those who have not scanned my previous build thread my main components were a 2000 Miata, LS1 engine and T56 transmission from a 2000 Z28, Getrag differential in conjunction with the various Flyin Miata Kits and V8 Roadster subframe.
It would be helpful to get some feedback to make sure the next build goes nice and smooth.
The Flyin Miata kits that were utilized for my first build are excellent quality pieces but there are other options that will also get the job done.
After reading over all of the build threads, both GM and Ford based, my head is spinning with ideas that might or might not work well together.

The time frame is up in the air but my intention is to start collecting parts this year and start the actual build some time next year since there is still an actual car to be located and purchased as well as the drivetrain pieces to be accumulated.
Haven't decided it I want to do a low budget build this time round or to go for a high performance build with a 600 HP drivetrain.
Both options are on the table.
One of the lessons learned from the first build is to buy and collect the major parts first and then start the build when everything is available.
It makes the build process much easier because not having some necessary items makes the build go in spurts of starts and stops in a very annoying manner.

There are several areas where the available options have pluses and minuses with the choices determining how well many of the other associated parts interact.

Off the top of my head, these are the components that I am trying to decide between various options.

Front subframe choices;
V8 Roadster subframe is a top quality and lightweight subframe but the rear bias of the transmission demands cutting and welding of the transmission tunnel.
Monster Miata subframe supposedly locates the engine forward far enough that no actual cutting of the tunnel is required.
How do the two compare with respect to overall quality and usability?
Presumably the more forward engine placement brings on other issues such as front accessory clearance to the radiator and fans.
Are there actual issues with fitting the radiator & fans?
Does the decreased clearance bring on heating issues?
What about interference issues for exhaust headers with the Monster subframe?
The forward bias of the Monster subframe would put the weight bias further forward. It is my understanding it makes about a 3% difference (51% to 54%) based on some weight threads I have seen on the internet. Is this a real world problem or just of interest to a road racer?

Transmission choices;
T56 seems to be the default transmission for LS based drivetrains and is what I used for my first build.
What about a built T5 such as is utilized on some of the Ford builds?
What about the CD009 manual transmission from Nissan 350Z or Infiniti G35?
One thing I haven't looked at real hard is automatic transmissions as they seem to need more space than the Miata has available.
Is there a good quality and compact automatic transmission available?
Any other reasonable possibilities to be explored?

Rear Differential choices;
My first build utilized a Getrag differential that was used by GM for various applications, most notably the 2004-2007 Cadillac CTS-V
All I am aware of beyond that is the Ford 7.7 or 8.8 choices.
I believe the 8.8 has an option for an electric locker that is not available on the others, correct?
The down side for the 8.8 is size because it uses up real estate the exhaust system really needs.
The 8.8 appears to be the choice for higher power output as it can handle more torque than the others.
Any other reason to go with any of the three over others?
Any other reasonable options?

Exhaust choices;
For my first build I went with the high quality (and expensive) option of Flyin Miata stainless shorty headers and stainless exhaust system.
Absolutely a great way to go if you are willing to spend the money and are using the Getrag differential.
Factory G8 exhaust manifolds supposedly will work with the Monster Miata subframe and would presumably be the low dollar budget choice.
Will they also work with the V8 Roadster subframes?
How much of a horsepower hit are you actually taking in the real world?
They come on a car that is rated at 400+ HP so my presumption is that they flow well enough to not be much of an overall restriction.
If headers are utilized, what headers will definitely work with the Monster Miata subframe?

All of the above items (subframe, transmission, differential, exhaust) tie in together with respect to clearances and difficulty to make everything play nice after it is assembled.
What I am trying to figure out is workable options to the Flyin Miata specific components without bringing on too many problems.

Engine options;
For my first build I sourced a salvage yard LS1 from a 200 Z28 that has low miles.
Power is good and weight is about as light as you are going to get with a V8.
The plug and play option is to spend a bunch of $$$ to buy a crate 535 HP engine or to buy a built aftermarket engine assembly that is good for 600+ HP.
The low budget choice would be to come up with a cast iron salvage engine and give it a rebuild with an upgraded camshaft and intake.
I learned my lesson about buying salvage parts without taking the additional step of rebuilding the assembly because two of the three salvage pieces (transmission & differential) that I bought ended up failing shortly after being installed.

Any ideas on specific assemblies mentioned above or even a full list of how you would recommend that I proceed?

acedeuce802

I'll comment on what I have experience with. I think figuring out whether it's a budget or all-out build will really drive a lot of these decisions. Also, will this be a street or track car?

Transmission choices: I looked into this for a while to try to save cost, and ultimately ended up with a T56. Part of me is regretting not going with a CD009 (mostly for cost of replacements down the road) but upfront cost of other transmissions basically end up the same (once you factor in needing an adapter kit, shortening the shifter mount, etc, but will beat a T56 in cost when you need to replace/rebuild it). Check out my gear analysis of CD009 vs T56 in this thread here: https://forum.miata.net/vb/showthread.php?t=662255 The CD009 would likely drive what diff you use based on gearing available. A T5 would depend on your direction for the build, if you want to make good power then don't consider it. Maybe look into BMW trans options. It looks like there is an adapter kit available.

Rear differential: Anything besides Getrag or Ford is going to require custom fab and axles (except an RX7 TII, but there's only certain situations where that makes sense). The actual housing doesn't matter performance wise, so I would start with the performance attributes that would match the car. Do you want a clutch pack for straight line? Do you want a well tuned road race tuned clutch pack for track (like OS Giken)? Torsen? Then figure out which diff can make that happen. Getrag is either open or standard clutch pack (decent road race tune, can be tuned in the right hands). Ford has essentially unlimited options.

Exhaust: It looks like G8's with the LS3 dyno around 350whp stock, which is actually pretty poor for that motor. Long tubes compared to stock manifolds is typically around a 20-30hp bump, and would help let a cam/other supporting mods breath better. Stock manifolds would be a decent way to go for a budget build, but if you're putting this much money/time into a build, I'd at least do shortys at minimum. Not sure about clearance to Monster Miata subframe. I decided long tubes fit my build the best, so I built everything around the V8roadster subframe/longtubes.

Engine: I think there should be an in between option. If you choose a budget build, it doesn't mean you have to choose iron block. There are salvage aluminum 5.3's that are only a couple hundred more than an iron block, which is a very small price bump compared to the cost of the build. Especially since budget build means Monster Miata subframe, an iron block right in the middle of the engine bay will have some big impacts on weight balance.

What is your goal for this build? Are you keeping the old one? I don't see why you'd want to do a budget build, just seems like a waste of a build since you already have a nice one.

BGordon

Not real sure of the exact direction for the next build, which is the reason for starting a thread.

It will be a street car 100% and nothing else.
If I go the high output route it will probably be more drag strip focused and would also probably use the Ford 8.8 differential with electric locker.
Never owned an 11 second street car and a Miata seems to be a reasonable way to get there.
Low end budget build would just be an entertaining street car, noisy and rowdy and fun as hell to blast around town in.
Sort of a motorcycle with too many wheels since my wife will not agree to me getting a cycle.

Haven't decided on the fate of my present car because my as the build progressed it turned much more away from a budget build daily driver and towards a weekend and nice weather toy.
The Thunderbolt video series was my inspiration and my car ended up mimicking that car with less HP and a car that was not in as good a condition as his MazdaSpeed.
It is too nice to kick out of my one car garage and leave outside while doing another build so all in all I am leaning towards selling it.
I call it a "Older Gentleman's Sports Car" because it looks and sounds and drives very much like a stock car should but has the performance and handling of an AC Cobra.
It is an annoyance to go top up-top down repeatedly as is required for a daily driver when you enjoy driving with the top down so I just leave the top down and only bring it out in suitable weather.
It is really easy to drive around in traffic and forget what can happen when you put the pedal to the metal.