When you talk to Honda enthusiasts, the J series lives in a weird area. Most people don’t really think about them, but most people think they’re insanely interesting to shoehorn into a 92-00 Honda chassis. The problem is, without the popularity of the J being that of the typical K,B, or even H swaps, documentation on these swaps is few and far between. In this guide, my goal is to demystify the J swap to make it much less intimidating for anyone interested.

During this guide, it would be ideal if you have K swap knowledge, but it isn’t a requirement. A lot of pieces of this puzzle will be equivocated how to do a K swap because the two are similar in concept. (Dropping in the engine and rewiring the chassis to talk to the engine harness/ecu). What you’ll gain from this guide is also an understanding of how the electronics on a Honda work and in theory, will give you the tools needed to swap ANY engine in this chassis wiring wise.

Understanding The J Series Engine

The J has been in production since the mid 90s and is still in production to this day (2023). With over 27 years of advancement, the motor has gone through several iterations. Typically, with J swaps, people tend to stick to the ‘1st generation’ motors, and most swap parts are built around those motors. In this guide we will be mainly focusing on the ‘2nd generation’ or ‘revised bellhousing’ engine. Specifically the J35A8. I will take time to note when you should consult the factory pinout for your specific engine when the differences arise. Most of the differences will exist almost solely on the wiring side.

The Engine and Transmission

When sourcing a motor, the most common and desirable engine swap is the J32A2 from the 01-03 CL Type S or 02-03 TL Type-S. The main reason being the engine has a good amount of power potential, and comes attached to a 6 speed LSD transmission. This engine is the equivalent to a K20A2 swap in the K series world. It has everything you need, and almost all swap kits are built around this particular engine.

For my build, I happened to come across a J35A8. The J35A8 is the 3.5L powerplant from the 07-08 TL-Type S as well as Acura RL. The 35a8 is a ‘revised bellhousing’ engine. Around 2007, Honda changed the bellhousing of all the J series engines. So for a revised engine, the motor and transmissions are not interchangeable. 

When choosing your engine, the big reason people like the 32a2 is because it’s compatible with widely available transmissions outside of just the 6speed LSD. You have multiple other 6 speed and 5 speed options available from other cars. On the revised engines, your options are more limited to the TL. (All TL 6 speed transmissions on the revised motors have LSDs) the Accord, and some other models. But comparatively speaking, there is far more interchangeability between the pre revised motors.

The other major difference between the two engines is the cylinder head design. The pre-revised engines are ‘3 port’ heads. Meaning each individual cylinder has it’s own exhaust port and exhausts from the engine using a traditional header. In ~2007 Honda revised the exhaust port design on the head to the mono-port head similar to all their current models. The 2007+ engines all have a single downpipe leaving the cylinder head as the ‘header’ is integrated into the cylinder head. Unlike the K series, The Honda J series monoport heads still flow a tremendous amount, and in fact, some of the monoport heads make the biggest power of all the engines. So don’t let the head port dissuade you from electing the revised engine.

Engine Mounts

The skinny: Hasport mounts

Engine mounts are the standard honda swap affair. Just like the K swap, you cut the passenger side mount, and bolt on a new bracket. The K and J swap mounting situation is more or less the same with different mounts. Unlike the K, all the J series manual transmission can use the same mounts, so there’s no mixing and matching mounts. My suggestion is Hasport, but innovative does also offer another option. With Hasport’s ‘J2’ series mounts, the mounts are dual slotted allowing the engine to be mounted in 2 positions. Unlike with the K series, where the mount holes are for K20 vs K24, the J series dual drilled mounts are for mounting the engine in the standard swap position that requires cutting of the hood vs. low where the engine sits below the hood. The tradeoff in play is that while the lower mounts allow you to close the hood without modification, the oil pan gets dangerously low to the ground.The tradeoff and pros/cons are ultimately up to you. Most tend to elect to run a cut hood vs. blowing a hole in their oil pan. A racecar that isn’t on streets where obstacles become issues, but elect to run under hood knowing they aren’t going to hit a random concrete block in the middle of the road.

Axles

Quick Answer: Buy prebuilts from insane shafts or driveshaft shop.

Axles were one of the weirdest struggles I had to deal with on my swap. For axles, you can hobble together your own combination. For my 98 Integra, I used 2005 RSX Base axles and removed the inners, and took my stock J series inners and swapped them on. Some people have mentioned using early 90s Accord LXi model axles and swapping those out. There’s several approaches. The easiest way is to simply buy swap axles from Insane shafts or Driveshaft shop. But if you have too much time like I did to buy 10 sets of axles and plug and play until you got correct fitment, go for it.

Wiring

Unlike most swaps, the J has little to no easily available aftermarket support. Documentation on these swaps is few and far between especially in this regard. I’ve tried to make it a bit easier to understand or at least give the tools needed to understand the theory of the wiring for the swap. There are multiple ways to do it, and there is most certainly a cleaner way to do it than I did, but this way is certified working.This wiring is specific for the J35A8 swap into an EG or 94-01 Integra. I might add the pinouts for EK eventually.

What you’ll need:**J Series ECU Header (K series non DBW is the same)

[picture of j series ecu header]

Honda C101 Plug (can get these on ebay or amazon for ~$20-30)[picture of c101 plug]

Wire Strippers

Solder

Soldering Iron

Heat Shrink

20-22ga Wire

Crimps (optional)

Wire Crimpers (If using crimps)

I strongly suggest you watch a video to understand the general concept of building a jumper using an ecu header, as all those concepts apply here. 

**You can obtain an ECU header from a cheap K series or J series ECU at a junk yard using the technique in the video above or use a header. Just make sure the ecu uses the same plugs as your engine harness

J Series Swap Wiring Pinout

Step 1 Prepare For Chassis Wiring

For EG/DC, remove the driver side kick panel and remove remove the 2x 20pin connectors back deep in the dash. You should see a brown/maroon colored 20pin connector. Underneath that connector is a white 20 pin connector. You will probably have to unplug the brown connector to reach the white one, just make sure you plug the brown one back in afterwards.

With the white connector disconnected, you have 2 options, you can either purchase a new honda 20pin, or you can cut the existing one off, and splice wires into it. I strongly prefer buying new so I can revert back the wiring at any time, but it’s up to you. The white 20pin is where all the wiring to translate to our chassis will occur. This is where we will pull power to run the ecu, power the engine harness accessories, as well send signals to the cluster.

Step 2 Build the Jumper

Once again, I am going to suggest you watch THIS VIDEO about wiring your own jumper. For the J35A8 swap, FOLLOW THIS PINOUT. For other swaps, reference a manual, and find all the individual pins by using my 35a8 pinout as reference. In the future, I might make additional pinouts for additional engines.You’ll build the jumper using the Honda K/J series ECU Header and following the video above.

Step 3 Wire the Chassis Harness

On the pinout you opened in step 2, click over to the 2nd sheet for chassis wiring. The chassis wiring will be built off the white 20pin connector you removed for step 1. This harness will run from the driver side kick panel all the way over to the passenger side, so make sure you’re provisioning for it.Note: Only plug A,B,C are needed. D and E can be ignored.Some notes: For your tach signal, the J series uses a 6 cylinder signal for tach output, so it will not match your civic/integra 4 cylinder input. This can be translated using a translator, OR, some ECUs, like the Haltech Elite that I used offer the translation in the ECU itself. The same applies for displaying speed on the factory cluster as well. On my particular motor, a translator is required to convert the high frequency signal to a low frequency signal. The Haltech handles this as well.

Step 4 Odds and Ends

After the jumper and chassis harness have been wired, there are a couple more wires that need run. Coil Power and Alternator signal. The coil power will be a black/white wire on the big 3 plugs at the chassis connector. The picture is available on the spreadsheet. You will wire that wire to a switched 12v, I ran mine to the dedicated 12v coil power off the chassis plug. For the alternator signal, you will need to grab the black/yellow wire off the green plug and run it also to a switched 12v. You can run it to the same 12v as coil power.On my swap, I had to make a new wire for the starter solenoid. A simple female spade connector will work. Just connect that to the solenoid input, and run a single (I used 18ga) wire to the starter output on the chassis harness.

Fueling

Fueling these cars is almost exactly like a K series. The J35A8 from the factory is a returnless style setup, I opted to convert to a return style setup.

What’s needed:

Fuel Filter Banjo Fitting (M12x1.25 Banjo to 6an)

6AN Hose Ends

EFI -> 6AN Fitting6an hose6an hose ends

6an >¼” barb fitting

¼” fuel hose

Fuel pressure regulator

Pretty straightforward. You connect the banjo>6an fitting to the fuel filter. Run a hose from the fuel filter to the inlet side of the regulator. Attach the EFI>6an fitting to the factory hard line off the engine. Run the other side of the regulator to the fitting you just attached to the factory hard line. 6an>¼ barb goes to the outlet side of the regulator, and run a hose from the return side of the regulator to the factory return hose.Clutch Line

This one is super simple. Buy a K Swap braided clutch line and use that. Direct bolt on.