DIY: Install a 3.5 RL engine in your 91-95 Acura Legend

Mike Diaz

Junior Member
How to install a 96-04 3.5L Acura RL engine into a 91-95 Acura Legend
Things you need:
96-04 RL block (EDIT: 02-04 RL engines were rated with more horsepower & Torque, but it was related to muffler and ECU changes, not engine design. This will not benefit you with Legend electronics and exhaust.)
RL heads
RL driver side valve cover
RL intake manifold
RL throttle body
RL timing belt covers
RL egr valve
RL passenger side front engine mount
RL exhaust manifolds and 02 sensors (optional, but I used them)
RL fuel rails, fuel pressure regulator, and fuel damper (optional, but I used them)
RL timing belt and tensioner
RL balance shaft belt
Legend Coil packs
Legend passenger valve cover & sensor
Legend wiring harness
Legend injectors
Legend alternator
Legend power steering pump
Legend A/C compressor (if equipped)
Legend differential
Legend front driver side engine mount
Legend front passenger engine mount
Legend axles
Any Legend transmission will bolt up to the RL engine. Only one bellhousing bolt will not line up. Ignore that one bolt.

You do not need:

RL differential
RL injectors
RL wiring harness
RL coil packs
RL ECU & ignitor. (Anything that isn't connected to the engine)
Buy an engine stand and mount the RL engine to it. Then strip the engine down to the Block, heads and the driver side valve cover. Yes, the intake manifold should get new gaskets. Get your passenger side, front engine mount cut and welded so that the RL engine mount side bolts to the engine, and the Legend mount side, bolts to the rubber mount (see pictures for 91-93 Legends).
Now is the time to clean and paint your engine if you want. I used High temperature low gloss black paint on the block and heads, and VHT gray wheel paint on the valve covers, intake manifold, and the timing covers, and it turned out good. You can do any color, just make sure it's quality high temp paint. This may also be a good time to change the spark plugs (NGK or Nippon Denso only), timing belt, water pump, balance belt, and tensioner.

Get new intake manifold gaskets and reinstall your intake manifold with new gaskets. Install the LEGEND injectors and the RL fuel rails (optional) on the intake manifold. The intake manifold will have vacuum tubes running off by each injector, cap those off. (I didn't, and those blue tubes that are capped off are the end result. I plan on capping them off at the injector housing when I pull my intake manifold again).

Install the LEGEND differential on the side of the oil pan, then install the LEGEND starter.

Once the engine is bolted to the transmission , you can install the LEGEND coil packs and the LEGEND wiring harness. Here's where it gets tricky. There's a few splices that must be made in the LEGEND wiring harness.

First, on the coolant connector tube that runs between the upper radiator hose and the heads, those two sensors are switched around, you'll need to extend the wires on both of those sensor plugs about 6-8 inches so the wires will reach the opposite side.

The oil pressure sender plug down by the balance shaft will need to be extended about 4-5 inches. Also, on that plug, since the power steering belt is so close to the timing cover, you have to run the wire out and zip tie it to the lower radiator hose and then plug it in (see pics)

The intake air temperature sensor that used to be on the front of the intake, is now on the rear of the intake. You'll have to extend that wire out about 10 inches to reach around the back side of the engine.

Swap the Legend valve cover onto the passenger side of the engine and use the original Legend sensor in the rear of that valve cover.

Go out and buy a small roll of vacuum tube ($10-12) and run your own lines where needed. Most of the original lines will match up. IF YOU GUT YOUR INTAKE MANIFOLD: You won't use a few of the lines if you gut the intake manfold. These unused lines lead up to the vacuum solenoids behind the passenger headlight and will get capped off at the solenoid.

The crank/cam position sensor behind the driver side cam gear has a plug that does not match the Legend wiring harness plug. You have to cut and match up all the wires, solder, then heat shrink the wires. The wires are the same color on each side, so matching them up is easy.

It's time to install the 3.5L engine! You will find that only one of the passenger side bell housing bolts will not bolt up to the 3.5L block. Don't worry, it won't cause a problem, just leave it with no bolt in it. Automatic Transmission: don't forget torque converter bolts - Manual Transmission: Don't forget to reinstall the slave cylinder and clutch fork.

Almost done. Next, you're going to take the Legend fuel line that runs from the fuel filter to the engine, and you're going to slowly bend it upwards, so it will match the RL's fuel rail (see pics). Bolt it down to the fuel rail with the fuel damper behind it. Make absolutely sure you don't kink this line. If you decide to use the Legend fuel rail, you will use your Legend fuel line

IF YOU USED THE RL FUEL RAILS: Last thing, on the RL's fuel pressure regulator, the vacuum line running off it is smaller in diameter than the Legend. Buy a vacuum line size reducer and some hose, and use a small hose clamp. Make sure it won't leak.

Double check all your connections, make sure all your bolts are tight. I use Mobil 1 Synthetic 5w-30. Triple check all your connections, make sure all your fluids are full, and cross your fingers. It may take a couple of cranks to start, since your fuel rails will be empty. If it does not start, check your fuses, relays, connections and PM me.

This swap is not beyond any person with some mechanical experience. Some simple wiring changes, a custom mount, and everything else pretty much bolts right up. Nobody should be scared of this swap.

Email me if you have any questions.

My engine bay

What the mount should look like when it's done (for 91-93 Legends only):

Excuse the following pictures, I drove in the rain a couple days ago, and my engine compartment is a mess

This is the oil pressure sending switch wire that needs to be extended and zip tied to the radiator hose since it can no longer be ran between the timing cover and the belts.

Some of the vacuum lines (I used the RL valve cover, which needs to be swapped back to the Legend valve cover)

A little adaptor I made for the undersized fuel pressure regulator tube (in red). This picture also shows the intake temp sensor (Gray) that had to be moved to the back of the engine.

The fuel line being bent up to fit on the RL fuel rail (OPTIONAL: use your Legend fuel rail and line)

The hybrid mount, painted and installed

These are the two sensors that are swapped (in the thin red circles). You have to extend the wires about 6-8 inches to make it work

A pic of my car on the Dyno:

Scans of my first dyno run. This is untuned (AFC-II set at zeros), with one piece CAI, EGR Blocked, Throttle Body coolant bypass, Gutted and gasket matched intake manifold, gasket matched and lightly ported exhaust side of the heads, ported exhaust manifolds, stock Y pipe, no cat, and 2.5" exhaust from Y pipe back.

Torque curve with air fuel ratio

Max horsepower and torque

Air/Fuel Ratio (terrible)


My dyno thread: Dyno Results for the 3.5L swap - The Acura Legend & Acura RL Community
Pics on the dyno: 2 pics of my coupe on the dyno - The Acura Legend & Acura RL Community
3.5L swap general questions: 3.5 swap questions - The Acura Legend & Acura RL Community
Video of my 3.5L coupe in action: I made a "Legend only" video out of yesterday's vid. - The Acura Legend & Acura RL Community
Thread about my vacuum problems and install issues: Christian, I need your help big time with this 3.5L swap *UPDATE, SHE RUNS PERFECT!* - The Acura Legend & Acura RL Community
Problems when I first got it running: She's alive - The Acura Legend & Acura RL Community
Thread about the mount: For future 3.5L swaps: Here is 5 pictures of what your mount needs to look like - The Acura Legend & Acura RL Community
Honda Tuning working on a supercharger manifold: Honda Tuning Oct2006:Custom supercharger - The Acura Legend & Acura RL Community
Christian's superthread about the 3.5L swap. None of this would be done without him. Dv8's Legend (Chronicles and Articles) - The Acura Legend & Acura RL Community
Member from Thailand with a friend's 3.5L Swap: Hello from Thailand - The Acura Legend & Acura RL Community
HarlemLegendz 3.5L swap: rl swap done - The Acura Legend & Acura RL Community


My name is Byron.
I live 5 minutes from the Akron Horsepower shop. Kinda cool, hopefully I see that car around town.


New Member
If i have a 95 legend coupe will i need to modify the mount on the 3.5 rl motor? Also how did you gut the manifold? Was there any extra plugs from the type 2 air intake system? If so will that effect a chack engine light? Can u use the complete rails and injectors from the 3.2??- thanks for the great info- i greatly appriciate it!!

Mike Diaz

Junior Member
If i have a 95 legend coupe will i need to modify the mount on the 3.5 rl motor? Also how did you gut the manifold? Was there any extra plugs from the type 2 air intake system? If so will that effect a chack engine light? Can u use the complete rails and injectors from the 3.2??- thanks for the great info- i greatly appriciate it!!
Yes, the mount on the passenger front side of the engine is totally different on the 3.5L engine because of the addition of the balance shaft. It still has to be welded.

You can either reuse the TCS or eliminate it by removing the intake tubing and just leaving them unplugged. You will have a TCS light on the dash if you do this. You can use the Fuel rails from the 3.2L but if you do that, you should use the 3.2L intake manifold because the fuel rails bolt to the manifold


New Member
the legend lover

Okay i got it now, mr, diaz, i need to know, i have the 2000 rl motor, trans, computer, everything, i need to know what should i put in my legend to get the best performance and how to put the motor in my legend just for basic driving. But i want the torque and power.