1 2
Poser71 None
5/14/12 9:56 p.m.

Hello world,

clearly new to the board and the community. I am helping a friend do a monster miata build. OK I am pushing relentlessly to have him do this build and finally he is consented

So now down to brass tacks, what is the best option for sourcing a engine and transmission for the build. My thought was to get a salvaged corvette thus getting a engine and transmission and wire harness all in one shot. I realize that there may be other options like an LS motor from a truck but that leaves me with where to get the transmission and harness.
So in short what is the easiest most cost effective way of getting these parts?

Learn me auto part sourcing for a monster miata build PLEASE!

Javelin GRM+ Memberand UltimaDork
5/14/12 10:11 p.m.

Corvette won't help you, it has a rear transxale. It's still just a T56 but you'll have to buy enough parts to make it not a good choice (accessory drives, bellhousing, tailshaft, oil pan, etc).

The "best" bolt-in choice is the LS1/T56 or LS2/T56 from a GTO, but because of that they bring $$$. The older LS1/T56 from the 98-02 Camaro Z28, SS, and Trans Am / Formula Firebirds is a close second. Deals are getting harder to find, but they exist.

Most people have to buy a truck motor and source all the other stuff separately.

JoeyM SuperDork
5/15/12 4:53 a.m.

Thanks, Javelin.

[See, I told you that the GRM guys know everything.]

For the record, the OP is my best friend. More importantly to GRM, he used a wooden hammer and english wheel to remove a 90 degree bend from sheet metal off an air handler so I could make a door skin.

Gasoline Reader
5/15/12 8:48 a.m.

If it was me, I would source a aluminum block and head 5.3l motor. RPO code L33. They are half the cost of a LS1 and 310hp. Find them in extended cab 4WD Silverado/Sierra pickups 2005-07. Search here:


belteshazzar UltraDork
5/15/12 9:36 a.m.


i second that

Keith GRM+ Memberand MegaDork
5/15/12 9:55 a.m.

Keep in mind that you'll have to change the oil pan, intake manifold and accessory drives off that L33. And as someone who has both an LS1 and an L33 in similarly sized cars - the extra torque of the LS1 makes its presence felt. I really wish I had the bigger motor instead of the L33.

I bought a driving 1998 Camaro for the donor for the MG. It let me drive my engine and trans to make sure there were no problems. I pulled out what I needed (in my case, the engine, trans, wiring, PCM and differential) and sold the shell. I could have made more from parting out the shell had I been willing to try, but even dumping it for $500 still got me the drivetrain for less than the price of junkyard parts would have been.

Given the packaging of a first-gen Miata, you'll want to convert any engine to the serpentine belt alignment from a Corvette. It's about 3/4" closer to the block than the Camaro and GTO setup, and that space is really handy for things like a radiator. We use the Cadillac CTS-V accessory package for Miatas. If I remember right, you need to swap the crank pulley, the complete accessory package (or alter the mounts) and the water pump. The best engine to start with would be one from a Corvette, but you'll have to find the transmission elsewhere.

You want the Camaro/Firebird version of the T56 if possible. The GTO is a second choice, as you have to change the shifter in order to have it come up through the Miata's shifter location.

JoeyM SuperDork
5/15/12 10:07 a.m.
Keith wrote: And as someone who has both an LS1 and an L33 in similarly sized cars - the extra torque of the LS1 makes its presence felt. I really wish I had the bigger motor instead of the L33.

How big of a difference would he feel between the LS1 and the L33 in street use? He swears it will never see any track time. (....and yes, I'm trying to convince Poser71 of the folly of that form of thinking.)

Keith GRM+ Memberand MegaDork
5/15/12 10:12 a.m.

That's where you really feel it. Wound up to 6000 rpm on the track, the L33 feels pretty strong. At 2000 rpm, it's fast but not gobsmacking. The LS1 (mine has a mild cam and mild headwork according to the paperwork) will push you back into your seat. It's enough of a difference that long-term plans for the Miata include changing out the L33 for something bigger because my street MG should not be faster on the street than my race car.

You can use the F-body oil pan in a Miata swap if you do a bit of modification (or buy the modified one that I have in my garage, when I think about it), but with an L33 you need to budget for that intake manifold and pan. Take that into consideration as you look at those $800 junkyard truck motors.

Greg Voth
Greg Voth HalfDork
5/15/12 10:15 a.m.

I don't necessarily disagree on sourcing the L33 but keep in mind the cost of sourcing non truck accessories, intake, T56 etc.

I am not all that far from you and had sourced L33's for around $800-$1200 but the RX-7 conversion calls for the Camaro/Bird accessories intake and pan. These would have cost me at least another $500.00. Then I still have to find a T56.

As it was I found a 98 Camaro LS1/T56 in a yard about 15 miles away. Asking $3700 for the motor and trans. Negotiated it down to $2500 if I pulled it. They let me take the car for a month to strip it. I've sold about $350 in parts off it and probably have another $300 or so I can sell off it. That ended up being the cheapest option for me but not typical pricing.

Edit: Looks like Keith beat me to it.

JoeyM SuperDork
5/15/12 11:10 a.m.

So what I think I'm hearing is:

1st choice: GTO bits (single donor)
2nd choice: 98-02 Camaro Z28, SS, and Trans Am / Formula Firebirds (single donor)
3rd choice: 'vette engines with other transmissions (multiple donor)
4th choice: L33 truck parts

Is that an accurate summary of the GRM concensus?

nickt93 New Reader
5/15/12 11:14 a.m.

Also, if you are looking for a less expensive transmission option, you can use the V8Roadsters bell housing to adapt a T5 to the LSX motor. Nowhere near as sexy of a gearbox, but damn cheap.

Javelin GRM+ Memberand UltimaDork
5/15/12 11:20 a.m.

In reply to JoeyM:

I'd probably put the 98-02 f-body first as most swap use their accessories and oil pan, plus the shifter is good. IIRC, the GTO shifter location is all in the shifter itself, so you can just plop the f-body one on to change it, but the 05-06 LS2's are DBW which usually means buying a regular TB or swapping in a whole harness.

As for the trucks, a lot of people prefer the 6.0 truck motors, especially for turbo builds in the iron block version. The L33 is just an all-aluminum 5.3, they make an iron 5.3 as well.

CTS-V is another good single-donor source, especially for IRS cars, but they are far less common and usually more $$$. Early ones were LS6 (405HP Z06 motor), later ones (05+) were 400HP LS2 DBW motors.

SSR uses the GTO drivetrain IIRC, but good luck finding one in a JY. Same story with the G8 GT (auto only), G8 GXP (very few manuals), and the new Caprice (auto only).

Keith GRM+ Memberand MegaDork
5/15/12 11:33 a.m.

The CTS-V trans needs a new tail section to work in a Miata, so it's not a good single-donor option. Although it will give up a good diff and has the right accessories. Given the problems with the early CTS diffs, I'd just pull the motor and wiring out of a junker and buy a new diff from GM. They're surprisingly inexpensive.

I never got to the point of driving my car with a T5, but it's going to be more expensive than you think. First you have to beef up the T5 to survive an LS motor. Then you need a $400 release bearing. And then you have to buy the Quicktime bellhousing and a custom clutch. Once that's all done, you've got the shifter sitting about 4" too far forward so it won't fit with an interior.

We use DBW engines in our swaps at FM although my own car has a cable. It's not a big deal, you just install the DBW pedal in the car and run the wires to the PCM. My biggest complaint is that the pedal has too short a throw, I like a little more travel if I'm trying to negotiate that much power in that light a car. But otherwise, I have no problem with the DBW.

Javelin GRM+ Memberand UltimaDork
5/15/12 11:35 a.m.

Not saying DBW is a big deal, just that it's another thing to think about. Most people swapping them either go hole-hog and keep the entire system with all the sensors, wiring, etc or yank it for a cable setup and aftermarket ignition/etc. Just another step in the process and possibly more parts to buy or source.

Keith GRM+ Memberand MegaDork
5/15/12 11:40 a.m.

But we don't need to be most people Why not just pull the pedal (or buy a new one from GM) and wire it in? Shouldn't be challenging.

Javelin GRM+ Memberand UltimaDork
5/15/12 12:16 p.m.

In reply to Keith:

It's challenging when you buy just a motor instead of a whole car for the parts. Which is how most LS swaps are done.

Keith GRM+ Memberand MegaDork
5/15/12 12:31 p.m.

But you're buying the wiring anyway. So you just buy that wiring as part of it. It's as challenging as saying "I also want the pedal and the wiring to it".

My perspective is a bit off, of course. I've done a single-donor LS swap and crate motor swaps. The first LS swap we did at FM was a multiple-donor one using a 2002 Firebird engine and PCM we ordered from a junkyard - I have the wiring from that swap in my Miata. (edit) But I've never gone and peeled a car apart at a junkyard. I just ordered what I needed or used the complete car (end edit)

The crate motors came with a swap-specific PCM and pedal from GM, very easy to deal with. If you can swing the cash, I strongly recommend this route. The multiple-donor one was as easy as saying "we need these parts". The single donor was the hardest from a wiring standpoint, as I didn't know just how much wiring I was going to need at first so I really dug into that poor Camaro and ended up with a lot more than required. I do tend to be a little more comfortable with wiring than a lot of muscle car guys, I'd never consider putting a carb on an LS motor like a lot of people do.

Osterkraut UltraDork
5/15/12 12:37 p.m.
JoeyM wrote: So what I think I'm hearing is: 1st choice: GTO bits (single donor)

I don't understand how if you have to source different accessory belts and a tailshaft, the GTO makes the best donor. Is the engine THAT much better?

JoeyM SuperDork
5/15/12 12:56 p.m.

^^^ wants to know the same thing. (...and why the heck you're quoting me. I don't know squat about this stuff.)

Javelin GRM+ Memberand UltimaDork
5/15/12 1:43 p.m.

In reply to Keith:

Dude, you've swapped infinitely more LS's than I have, I'm not going to argue with you. I'm just pointing out that DBW is an additional thing to think about. For some cars and some swappers, it's nothing. For others, trying to swap in a DBW pedal to their old car may or may not be worth it. Some JY's pull the motors and crush the cars, leaving no pedal available, etc. It's not right or wrong, just something to consider (just like different oil pans, different intakes, different accessories, different shifter locations, etc, etc, etc). We can even get into Gen III / Gen IV differences with clutches, balancers, reluctors, etc for those who are wiring from scratch or running MS, etc. It's just information, it's up to the end user to use it, interpret it, etc.

Javelin GRM+ Memberand UltimaDork
5/15/12 1:45 p.m.

In reply to Osterkraut:

Depends on the car being swapped into (some need the GTO's particular selection) or just straight availability (GTO's are newer and thus slightly more easily found as totaled completes right now versus the 98-02 f-body). Personally though, I agree, and think the 98-02 f-body is the easiest single-donor to swap from for the majority of swaps. Most setups seem to favor the f-cars intake, shifter location, oil pan, and even accessories.

Keith GRM+ Memberand MegaDork
5/15/12 3:51 p.m.

Sorry, that came out the wrong way - I edited part of the post as I wrote it, and it didn't come out right. What I meant about the comment in perspectives is that I haven't actually done a swap where I was crawling around a junkyard. I've ordered in the parts I've needed, I've stripped a complete car - but never gone looking with a toolbox.

If you're ordering parts in, I don't see the DBW being any more difficult from the buyer's standpoint. The junkyard might make their own life more difficult, but there are lots of junkyards that are easy to search, so that's their problem as you only have to make another phone call. You're doing wiring anyhow, two more for a throttle pedal isn't a big deal in the scheme of things. But I might be missing something. And since this discussion was specifically about a Miata application, I can say that there is no problem with installing the GM DBW throttle in a Miata. So it's not a big deal from that aspect.

You can get all balled up with different sensors and the like if you want to get fancy. Personally, I see no reason to go with something like MS on an LS motor, not when you can use something like HPTuners to do the exact same thing to the OE-quality stock PCM.

I'd call the F-body the best single donor. There is no true single donor out there for the Miata application, but it's got more of the biggest parts than anything else.

Javelin GRM+ Memberand UltimaDork
5/15/12 4:14 p.m.

Just to continue the point(s) further for future readers, in some cases you don't even need the DBW pedal (Hot Rod's LS7 into the Solstice for example) as the recipient vehicle is good-to-go. Sometimes the DBW pedal install is too much trouble (like with a bottom-hinged recipient car, like the Porsche 911 or 944) in which case it's easier to order an 04 GTO throttle body and use the cable setup that's already in the car.

It's a case-by-case basis thing. Each swap will have different needs for each end user, depending on their donor source(s) and recipient vehicle. This holds true for all of the parts utilized for the swap, including the engine itself. I'm sure you don't even use the same parts in each Miata swap Keith?

Keith GRM+ Memberand MegaDork
5/15/12 4:53 p.m.

I'm answering questions based on the specific question, you're giving generalizations Sure, on a 944 it might be hard to put a DBW pedal in the car. But it's not hard in a Miata, and Poser asked about a Miata.

We do use almost exactly the same parts in each Miata swap, actually. At least, we have after the first couple of cars. This way we only have to solve a problem once and it allows us to offer a more polished final product. We can also do things like have specific parts built for the swap such as our radiators, exhausts and even small brackets - they end up being less expensive and better than one-off fabrications.

Wanna see the list, right down to a $1.95 diode? http://www.flyinmiata.com/V8/costs.php

There has been slight evolution as we go, of course. We've developed an improved intake. The exhaust wasn't used for the first few cars before we got it ready. The bracket for the exhaust was recently redone for more strength based on my experiences with the Targa Miata. And we just did our first swap using a standard LS3 instead of the LS376/480 crate motor, and the improved light throttle driveability will probably make that our engine of choice for the future. But generally, any changes are of an evolutionary sort and not just a "let's make this different" type. Our customers are happy to get a well-tested product, and usually they're prototyped on our own cars first.

We stick with crate engines because we don't want to be responsible for whatever is lurking inside a junkyard one - and because our initial install showed that GM is a lot better at engineering than a lot of aftermarket companies. Every failure we saw on Elvis was directly related to the non-OE parts we put on/in the engine - PS bracket problems, rocker arms, CNC-ported heads that ventilated the water jacket into the intake port. Besides, it's hard to beat a two-year warranty on a 480 hp engine. People don't come to us looking for the cheapest V8 Miata, they come to us looking for the best. For the cheapest, you need to build it yourself. Although crate GM motors are less expensive than you might expect, as they're taking advantage of mass production. The LS3 crate engine could have just as easily ended up in a Corvette. Once an engine goes out of production, the crate engines change.

GM also supplies the PCM and wiring harnesses (and throttle pedals) as part of a supporting package for the engine. The rear diff is brand new. T56 transmissions are getting hard to find new, but we have a small stash of them. The Magnum that's now available is a bulky critter.

My own cars are different, of course. The MG is a one-off. The Targa Miata uses a lot of the standard FM swap parts, but the engine was at the request of a sponsor. The PCM and wiring was a matter of convenience, as we had it in the shop and we weren't willing to use it on a customer car.

Poser71 New Reader
5/15/12 8:33 p.m.

OMG You guys are AWSOME!!!! thanks so much for breaking this down so much. As my name indicates I hardly know my ... from a hole in the wall but much appreciate your willingness to share great wisdom. Many thanks and please keep the info flowing.

So what I have gathered so far is, if we are going to go after a single donor F-body is the way to go . . . . that being said is one year model better than another?

How many more major parts need to be sourced outside the F-body donor? We are thinking at this point with going with FM's LSx conversion kit so between the donor and the kit am I correct in thinking that the only other major piece missing is the dif? Please learn me more!

on a side note: Keith, You said you had a modified oil pan that you might be willing to part with ????

1 2
Our Preferred Partners