Vorshlag - 1st gen 86 with Honda J37 V6 - SCCA TT Max4 build

Project Introduction - October 9, 2025: Hello Grassroots peoples! I figured this would be the perfect spot to talk about a low dollar drivetrain swap.

We've got the 2013 FRS shown here that we bought in 2016 and originally planned to put a giant V8 in. My wife and I ran it in autocross and time trial for 2 years before yanking the FA20. It was a blast to drive, but we bought this car to use for our LS swap kit development work, and pulled the FA20 by early 2019. 

Owning another 800 hp time attack car (you have to HATE money to do something like that!) has cured me of that V8 swapped 86 fantasy. We got our kit development out of this car, but have been looking at alternative engines to swap in, hopefully something unique and plentiful where we could add something the 86 community might like. 

I have been endurance racing the last 2 years with 3 college buddies in this 2014 BRZ above, with FA20 power and 6 speed automatic.

There's already one GRM article I wrote about that car (and more in the can), and driving this 86 has been fun - and has reawakened my desire to do something fun with our FRS. We've also seen the fragility and scarcity of FA20 engines, with one engine failure in this car already.

So we're going in a different direction with this widebody 86. It already has MCS suspension, 18x12" wheels and 315mm 200TW tires. And now - plans for Honda V6 power!

Our FRS was ignored for quite a while, but after building several other SCCA Time Trial "Max" category cars, we decided to look at a less insane engine swap - to avoid having to replace the rear axles, differential, and so many things that big power demands.

The new 2025 Max category "formulas" pushed us to look for a 3.7L engine swap with an unmodified long block. 

We had seen the J-series Hondas in the past and I actually bought a busted but complete J37A1 in January of 2025, just to get some real weights. Sure, there was published data but I only trust weight numbers shown on a scale by people I trust (me). 

The video linked above explains how we chose this J37 engine, why we want to pair that with a 2009-11 RX-8 transmission, and a little about the class rules we will build around. 

In the 3 weeks since we decided to test fit this J37 into this 86 chassis for the first time (originally it was going into a BMW E30 we had), we've designed the bell housing and crank adapters. And yes, while there are a few solutions for this swap, none of them deal with the Gen2 J-series bell housing pattern or are built for the 86 swap specifically, and especially not with this transmission. We chose these drivetrain items after careful research and deliberation within our shop. 

This second video was a quick 2 minute update I made yesterday, and we're about to start cutting the giant slab of aluminum shown there to make the bell housing adapter. 

Word has spread after posting on socials about possibly doing this J-swap, and Link ECU has committed to help make this swap easier for the community by taking their plug-and-play ECU for the 86 (which allows the stock harness to control an FA20 with their advanced EFI, while keeping all CAN functionality like gauges, EPAS and ABS) and making a harness and firmware for the J-swap. That is super exciting, as wiring is always the most daunting task on any swap in modern CAN enabled cars. 

So this won't be some fire breathing, 800 hp engine swap, no turbos or built engines - just a mild mannered, very lightweight, 300 hp, SOHC V6 from a Honda minivan, placed as perfectly as we can into an 86 chassis with the goal of an livable swap that can be done without taking out a 2nd mortgage. 

This engine + transmission combo fits really well in this chassis, and should actually DROP weight compared to the FA20. Yes, I said what I said! 

Before you folks ask a ton of questions like "why didn't you 2GR swap it!" or "why not use a ZF 8HP trans!" please watch the two videos.

We went through a lot of scenarios, looked at half a dozen engines, before we settled on the J37. Costs, availability, low weight, and fitment into this chassis all played a part. We will share more here as the project progresses. 

Thanks for reading,

Terry Fair @ Vorshlag

Interesting- I looked pretty hard at the J series before ultimately deciding to adapt a 2GRFE for my (still ongoing) rally BRZ project.  I am modifying the firewall and using a different oil pan, though, so not really apples to apples.  That J37 pan looks much more Subaru shaped than the 2GR ones.

For what it's worth, the 2GRFE on my scale dressed with the same stuff as your engine was 314lbs.  The FA20 was 253lbs so I'm interested in where you're achieving the drivetrain weight savings- for example, my new driveshaft is a lot lighter and shorter and I imagine yours will be too.

¯\_(ツ)_/¯ said:

Interesting- I looked pretty hard at the J series before ultimately deciding to adapt a 2GRFE for my (still ongoing) rally BRZ project.  I am modifying the firewall and using a different oil pan, though, so not really apples to apples.

For what it's worth, the 2GRFE on my scale dressed with the same stuff as your engine was 314lbs.  The FA20 was 253lbs so I'm interested in where you're achieving the drivetrain weight savings- for example, my new driveshaft is a lot lighter and shorter.

Yes, I found your swap thread on these very forums, using the FWD Toyota 2GR engine.

We looked at the 2GR-FSE (RWD) V6, but the size and weight turned us off (and it made the same power). Might be ideal for your rally build, but we cannot just hack away the firewall like that, and that type of major fab work turns off a lot of potential swap enthusiasts. 

We have also not seen an FA20 weigh that little, and I show the weights we have taken of these engines in my first video.

The J37 oil pan being a "front sump" design was easier to fit around the funky 86 crossmember, which I show in my first video. 

With a simple modification to remove two rear flanges from the cast pan, it fits - as shown above with the RX-8 box mocked up. This simple change saved a LOT of time and hassle making a custom oil pan.

While the FA20 is immensely wide, the Toyota 2GR DOHC V6 is still significantly wider than the J-series. I've seen (but not taken directly) weights exceeding 330 pounds, and it makes the same horsepower. Respectfully, I'd have to see it on a scale with my own eyes. I'm just skeptical that a modern DOHC V6 is lighter than this SOHC V6. 

The compactness and lightness of the J37 is unmatched in modern V6 engines, and we're excited to see how this works in a track oriented 86. We wish you the best in your rally swap, but for our purposes and our customers, a truly bolt-in swap that fits under the stock hood is a higher priority for us. 

Cheers,

Fair

In reply to Fair :

The bracketry Toyota includes on the 2GRFE is big and heavy- that's probably most of the difference between my weight and the published ones online, since I have no reason to run a power steering pump or air conditioning compressor.  And you're right, I'm not selling anything and if I was "ok so hack the transmission tunnel out and move it all back a bunch" wouldn't be a great pitch.

The J series intake manifolds have always struck me as heavy, is there a bunch of relatively high up weight there you can easily throw away and replace with something lighter?

Well that's pretty neato.  What kind of cost for the swap kit?

¯\_(ツ)_/¯ said:

In reply to Fair :

The J series intake manifolds have always struck me as heavy, is there a bunch of relatively high up weight there you can easily pitch and replace with something lighter?

The J37 uses a uniquely light magnesium upper manifold, and supposedly the J30.J32/J35 folks try to use them? They also supposedly have a bigger throttle body.

I can't find a weight on it, so let me go measure it...

Hmm, 14.2 pounds. Not super light, and the runners are admittedly very long. And it was very dirty. 

The lower manifold is cast aluminum, but with fewer runners than a DOHC would have. We can legally modify or change out the intake manifold entirely for our SCCA Max4 class. 

I've committed to buying one of the P2R custom upper manifolds with shorter runners, and might send the lower to Sean Yearwood there to have it ported as well. I think his upper will fit under the stock hood better and could uncork some upper RPM power (but might remove some mid range, so we will need ot dyno test both uppers). 

Lof8 - Andy said:

Well that's pretty neato.  What kind of cost for the swap kit?

We have no earthly idea yet - as you can see we have barely begun the swap development. We still need to make engine mounts, transmission crossmember, CNC machine the bellhousing and crnak adapters, and more. 

This is super cool.  I thought of using one of these engines in my rx8 swap, but the gearing didn't make sense for my use case.

With the rx8 transmission and stock rear diff (assuming 4.10) and stock tire diameter, this thing will be turning 3800 rpm at 80mph.

Is this a concern at all?

What's the redline on the J37?  I couldn't find that info published in a quick search.  Assuming it's around 6500 rpm, top speed would be just under 140 mph in 6th gear.  Sounds about right for a fun road course car with 300hp.

wvumtnbkr said:

This is super cool.  I thought of using one of these engines in my rx8 swap, but the gearing didn't make sense for my use case.

With the rx8 transmission and stock rear diff (assuming 4.10) and stock tire diameter, this thing will be turning 3800 rpm at 80mph.

Is this a concern at all?

What's the redline on the J37?  I couldn't find that info published in a quick search.  Assuming it's around 6500 rpm, top speed would be just under 140 mph in 6th gear.  Sounds about right for a fun road course car with 300hp.

Honestly we haven't even looked at the gearing calculator yet. Again, we're only 3 weeks into this swap, and most of that time has been exploring things to physically install the engine and transmission into the car. 

The 2009 Mazda RX-8 6-speed manual transmission ratios are: 1st gear: 3.815:1, 2nd gear: 2.260:1, 3rd gear: 1.640:1, 4th gear: 1.177:1, 5th gear: 1.000:1, 6th gear: 0.832:1, and the Reverse ratio is 3.815:1

Well that makes first gear useless for autocross or track use, but 2nd-6th look like usable ratios with a pretty tight spread.

My current TT car has a 6 speed manual, but I've only ever used two gears on track: 3rd and 4th (it helps that it makes power from 3000-8500 rpm)

The J37A1 we're using (2007-09) is fairly simple, with port fuel injection and VTEC only on the intake side. This engine has a modest 6500 RPM limit, makes peak power at 6000 and peak torque at 5000. And it is a good bit of torque at 275 ft-lbs, but that's due to the long runner intake and 3.7L of displacement. 

Luckily the wider tires we run are also taller than OEM, so that will soften the somewhat steep 4.10:1 rear ratio in the factory diff. Again, we'll run the gearing calcs soon. 

Thanks,

Fair

More J-swap to 86 progress happening right now... 

Myles and Christian here at Vorshlag are CNC machining an aluminum version of the crank adapter (8 bolt J-series to 6-bolt RX8 flywheel) out of a chunk of aluminum we have.

If this works out we'll cut the real one from the chunk of steel I ordered - to have stronger threads, etc.

Bunch of weird hardware ordered and en route to be able to bolt this all up later this week. And we'll tackle the bellhousing adapter next. 

The much delayed RX8 clutch sl@ve cylinder arrived, and Myles took a bunch of useless brackets off the 2009-11 RX8 6-speed we bought last week.

The weight dropped nearly 5 pounds, down to 100.2 lbs. Stay tuned for more updates on our J37 to 1st gen 86 right here! 😎

Fair @ Vorshlag

This is super odd yet very cool combo

Ok, this is awesome.

How hard is it to find those transmissions? We thought long and hard about J-swapping our Miata, but went with the LFX ultimately because it came with a turnkey transmission solution instead of adapting something else. 

Tom Suddard said:

Ok, this is awesome.

How hard is it to find those transmissions? We thought long and hard about J-swapping our Miata, but went with the LFX ultimately because it came with a turnkey transmission solution instead of adapting something else. 

The 2009-11 RX8 came with the "good" version with about 2x the torque rating of the earlier unit (Mazda got tired of warranty claims and released a new box). I paid $800 for this one, and they do exist. But yea, the LFX has the Camaro 6-speed, which isn't half bad, and just "bolts on" since it came married from the factory. We looked HARD at the LFX, but we feel this J-37 will be significantly lighter and make about the same power (300-310 whp). We'll see! 

Mazda released this upgraded box for 2009, and they still sell it new - it replaces the 2004-08 6-speed without any changes, per the ad above. This $2618 was retail price on this site, but most shops can get these for about $2000 new, with the right Mazda account. This retial price is cheaper than the CD009, by the way (they have also gone up as the dollar has lost value). 

The early RX8 box is abundant and cheap - I found a pallet of 6 of these at one JDM importer for $500 each. They just have a lower torque rating. Is it enough for a J30, J32?, or J35? Maybe. Probably. 

Same place had shelves of JDM imported, low mileage J35 and J37 engines. I'm about to go hunting for the J37A1 variant we want soon, as the wiring harness that Link ECU is building is getting close, as are our bellhousing and crank adapters. Then we can work on accessories, belt routing, etc. The lump we have now can still be used for mockup, mounts, crossmember design, etc. 

I really want to get this car fired up before the end of the year, so we can campaign it next season in SCCA TT Max4 class. This will help "prove out" this swap, this RX8 box, and the Link ECU's plug-in capabilities. Much excite. 

Cheers,

Fair

I've been following the videos on YouTube. Good to see you here as well. Killer project.

Watching with interest...  It's always good to see more options on the market!

The S2 RX8 transmission is pretty good.  These guys in UK make adapters to help fit it to various engines:

https://www.rx8gearboxadapters.com/

Looking forward to seeing how this build works out.

Does this J series variant have the integrated exhaust manifold and singe large exhaust port exiting the head?  That'll make exhaust routing nice and easy if so.

In for updates! This looks like a really cool option for the twins.

Project update for Oct 22, 2025: We have been busy the last ten days or so with this swap. The crank adapter is machined and this morning we finished the bellhousing adapter.

The prototype crank adapter we were making was a little tricky, and the first one slipped in the jaws on the mill (trying not to mar the surface). We made some changes and the 2nd prototype machined perfectly. 

We made these from some scrap aluminum round bar we had on hand, and the diameter is smaller than the production steel piece will be - so ignore the relatively small flanges around the outer 6 holes. This is a rough prototype. 

The fit to the aftermarket RX-8 flywheel was perfect and the 1.4 pound crank adapter and hardware added to the SFI steel flywheel was still only 11.5 pounds total. 

Making the bellhousing adapter for the Gen2 Honda J-series pattern to the S2 version of the RX-8 transmission was trickier - we didn't have any scrap to use here, only a single chunk of aluminum we ordered. Engineer Myles had an idea to test our measurements (both manual and 3D scanned) and he made two sheet steel cutouts for each of the bellhousing patterns on our CNC plasma table. And sure enough, one of the centerlines was off by about .010" - scanning error. This is why we made templates. He re-made that one and it fit perfectly. 

After adjusting the adapter design, the 39.2 pound chunk of aluminum was clamped to one of our CNC mills and it was time to set zeroes, check tools, and triple check the CAM program.  

Over the last 2 days he carefully ran tests then cut the only chunk of aluminum we had this big (which took a week to get here and wasn't cheap). He got the technique down and slowly got both sides machined, drilled and tapped this morning!

The finish is amazingly good for a first prototype - it has an almost jeweled finish on the contours. Laid the two adapters out this morning next to the flywheel. 

It is crazy that 33.4 pounds of metal was machined away to end up with this bellhousing adapter. We saved the middle piece of the opening so maybe it will get reused in some way later. 

We had this all bolted to the engine before lunch, even with a custom set of dowels for the RX8 side (one was missing). We had already re-scanned the RX-8 sl4ve cylinder on the transmission to make sure there was clearance on the adapter. 

This is now all bolted up together (minus one custom starter bolt I just ordered), and weighed. This is a very light engine + transmission, and we hope to be under the weight of the FA20 that came out.

The assembled drivetrain went back in without incident, and with the radiator support out of the way it just slides right in. 

It is a little snug near the reverse mount starter, but a couple of swings with the 5 pound sledge will more than clear that. 

The engine is set back really far compared to the FA20 - it will be more apparent once we have the front end and radiator back on. 

We are 2-3 months away from this actually running, of course, but we'll be sliding this drivetrain back into our 86's engine bay this afternoon. Then we can start on the engine mounts, transmission crossmember and driveshaft design and fabrication. 

More soon!

Very cool!  I'm curious now as to the weight of various popular six speed manuals.  I'm guessing stuff like the T56 is much, much heavier..

That's kind of stunningly light.

Correct me if I am wrong, but the front of the engine looks like it is even with the back of the strut towers?  If so, that is amazing.  You'll have a TON of room for the radiator, maybe an intercooler, oil cooler, your pet dog, everything, really.  So far, I'm loving the idea of this swap as I just picked up my first J37 powered SUV (Acura MDX) and I am still amazed at the smoothness, power, and sound of this brilliant engine.  How much more fun in such a light package like this car!  Super :)

Love your content, Terry. Following with interest. 

DavyZ said:

Correct me if I am wrong, but the front of the engine looks like it is even with the back of the strut towers?  If so, that is amazing.  You'll have a TON of room for the radiator, maybe an intercooler, oil cooler, your pet dog, everything, really.  So far, I'm loving the idea of this swap as I just picked up my first J37 powered SUV (Acura MDX) and I am still amazed at the smoothness, power, and sound of this brilliant engine.  How much more fun in such a light package like this car!  Super :)

I just shot this picture today standing on my 2nd floor looking down at the FRS on the lift. I need to string out the chassis to show this better but 95% of the engine IS behind the front axle centerline. 

This is so very different than the Subaru flat 4 that comes in the 1st and 2nd gen 86 cars. Those engines sit a good 11" forward of the firewall, to clear the high mounted reverse starter and for other mysteriously silly reasons.

On this car (which we used for LS V8 development in 2018) we have a tubular front bumper and a heavily rolled radiator. And even with the much larger V8, there was still a lot of room for activities!

We have this carbon front bumper cover with side grill openings we could use for coolers, if needed. I got this to use with the V8 but it should work fine for the J37 and a front splitter.

As you can see with the V6 installed there is a huge amount of room in front. That should translate to better front-to-rear weight bias than the FA20 or our LS V8 builds. 

Both of my engineers working on this project are out today, but I've been ordering parts like mad. The proper alternator arrives today and a bunch of P2R parts are being ordered now. 

More soon!