Technical Articles Relating To Off-Road Vehicle Development

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3.4L V6 Tacoma Engine Conversion

Published by Trails Less Traveled on November 9th, 2006



We outlined some goals for the project on the drive home. First and foremost: this was supposed to be a practical, reliable daily-driver. Secondly, we had to build the truck with a realistic budget in mind. It seemed reasonable (to us) to spend about as much money rebuilding this old truck as we might pay for a newer, nicer, used truck. After all, if everything went as planned, we would end-up with a custom-built vehicle that would suit our needs perfectly. After bringing the drivetrain up-to-date, the stock suspension was next on our list of things that needed to be updated; so we ordered-up a long-travel IFS kit from Total Chaos with RaceRunner coilovers. In the rear, the idea was to keep it simple by using Deaver leafsprings with another pair of 2.5” diameter remote-reservoir RaceRunner shocks mounted under the bed. 33×10.5” BFG tires would get us anywhere we wanted to take this tuck and we knew they would handle great on-road.

You can see where this is headed. A quick Internet search turned up a promising ad: 1989 V6/5spd SR5 4Runner with a blown head-gasket and an asking price of only $900. We would have bought it in almost any condition at that price, but the truck was actually in pretty good shape. There were a few minor dents and one softball sized spot of rust on the rear quarter-panel from a leaky rear window washer reservoir. The interior was in pretty bad shape but we knew that finding inexpensive replacement parts wouldn’t be difficult.

The 1st generation Toyota 4Runner (‘84-89) was one of the all-time, best-styled, most functional SUV’s ever made. It was almost a perfect formula: a rugged chassis and dependable drivetrain components, two doors, four seats and a removable hardtop. The only thing missing was an engine. Sure, those older Toyota trucks might run forever, but don’t expect to get anywhere too quickly. Toyota’s 2.4L 22RE 4-cylinder engine (introduced in ‘85) peaked at about 100hp and 130lb-ft of torque. There was a turbo option (22R-TE) available in limited numbers from 1986-1987, which bumped the power up to 135hp and 173 lb-ft of torque, but it was only available with an automatic and there were some reliability issues with the turbo units.

Toyota introduced their 3.0L V6 (3VZ-E) in 1988, but the lack of power (150hp), poor fuel economy and tendency to blow head gaskets didn’t go over well with Toyota owners and the 3.0L quickly earned a reputation as somewhat of a lemon. Most off-road enthusiasts would opt for the trusty 4-cyl over the often-troublesome V6, feeling that the improved reliability and fuel economy was worth the small sacrifice in power.

In late 1995 (1995.5 model year) Toyota introduced the all-new Tacoma platform and with it came a revised and enlarged V6 engine (5VZF-E), based on the older 3VZ-E but heavily improved. The new engine grew to 3.4L of displacement and the power output jumped up to190hp and 220lb-ft of torque, all while achieving similar mileage as the previous offering. Over the past ten years, the Tacoma V6 has also proven itself to be much more reliable.

Externally, the 3.0L and the 3.4L are very similar engines. They share common engine mounts, oil pan and bell-housing bolt patterns. These similarities open up the door to a relatively simple engine-swap. Although the exhaust crossover, air-intake and battery are all located on the opposite sides in the newer Tacoma, the only real obstacle is the adapting the new engine’s wiring harness to the older chassis wiring-harness.

Mike Caskey, the owner of Off-Road Solutions, realized the potential of this engine-swap early on and began developing conversion packages ranging from basic kits that include the wiring harness and a few essential components to comprehensive kits that come with EVERYTHING required to complete the swap. All of their kits include step-by-step instructions and Mike welcomes customers to call his tech line for any additional assistance.

*See the Parts Included sidebar for a list of parts included in the complete 3.4L conversion kit from ORS.

We called a few Toyota salvage yards and determined that complete 3.4L engines with the wiring harness fetch anywhere from $1,500-2,500, depending on the mileage. We ended up sourcing an engine out of a wrecked ‘97 4Runner with about 70K miles from Central Foreign Auto Supply in Denver CO for $2,000, including all of the small parts that we needed and the shipping charges to CA.

*See the Parts Needed sidebar for a list of parts required to complete the 3.4L conversion.

We should note that while upgrading from the 3.0L to 3.4L is fairly straightforward, swapping a 3.4L into a 4-cylinder truck is a little bit more involved. New engine mounts will have to be fabricated and some parts, like a 5-speed transmission, will have to be sourced from a 3.0L donor vehicle.


We started by removing the hood to gain access to the engine compartment. Then we got to work disconnecting all of the vacuum hoses, wiring harness connections and accessories that needed to be removed before pulling the engine.

The stock radiator can be reused with the 3.4L and IWC Replica Watches
depending on the year of truck, the radiator fan and shroud can also be reused. Some earlier models used a fan that had a ring connecting the fan blades around the circumference. ORS told us that these older fans often become brittle and shatter. They suggest upgrading to the later-style 3.0L fan with individual blades (part#: 16361-65020). Our old fan is pictured on the left next to the new fan on the right. The yellow, chalky surface texture told us that our fan was ready to crumble.

Make sure to position a floor jack under the transmission before attempting to remove the engine. After double-checking to make sure that we’d removed everything connecting the engine to the chassis, we attached the engine to the hoist to the engine and unbolted the engine mounts and the bellhousing bolts.

All of the exhaust crosssover hardware was so badly corroded that we just cut the exhaust pipe about 1’ downstream from the collector and after some minor coaxing, we engine lifted free.

After the engine was resting safely on the ground, we removed the bell housing stiffening brackets to be reused with the new engine.

After the engine was removed, we set about cleaning up the engine compartment engine compartment. First, we sprayed everything down with biodegradable degreaser and then wiped all of the grease, oil and dirt from the frame and sheetmetal. After that we brushed some rust inhibitor onto the frame rails to eliminate a little surface rust in a few areas. After a final wipe-down, we masked and painted the framerails in sections.

The stock battery tray doesn’t need to be removed, but ours was rusty so we drilled out all of the spot-welds and painted the inner fender.

The stock power-steering lines are not reused, so we removed and discarded them.


With the 3.4L supported by the engine hoist, we began by removing the dipstick and tube, engine mounts, oil pan and pickup, clutch and pressure plate. All of these parts will be replaced with new parts supplied in the ORS kit. The stock 3.0L oilpan can be reused, but ORS sent us a new one so that we could store the old engine without opening the bottom-end to contaminants.

Our kit included a tap, plug, drill bit and adapter to relocate the oil dipstick tube. Some 3.4L blocks already have a hole drilled in the proper location, while others will have to be drilled. The location is very obvious and the instructions are specific.

The 3.0L oil pressure sender needs to be reused in order to get an accurate reading at the gauge. Luckily it bolts right up to the 3.4L, but the connection does need to be spliced to work with the new engine’s wiring harness. ORS also supplied us with a fresh OEM oil filter that we went ahead and installed while the engine was out.

We used the supplied liquid gasket to lay a thick bead around the rim of the new oil pan and then we attached it to the 3.4L block.

We bolted-up the replacement rubber-insolated engine mounts to the stock 3.0L perches and moved on to the clutch assembly.

The 3.0L flywheel needs to be reused. It should be inspected and machined before installing the new clutch assembly. Getting the old pilot bearing out is a little bit tricky if you don’t have the proper bearing puller. We packed heavy axle-grease into the center hole until the void behind the bearing was completely filled. Then we took a bolt that was exactly the inside diameter of the bearing hole and gave it a quick tap with a mallet. This slowly forced the bearing out. We continued adding grease and applying pressure with the mallet and bolt until the pilot bearing came free.

We used a socket with the same outside diameter as the pilot bearing’s outer race to drive the new pilot-bearing in place.

We installed the new clutch using a universal clutch alignment tool, with has proven to be a much better value than buying a different clutch alignment tool for each vehicle that we work on.

A large flat-blade screwdriver can be used to keep the flywheel from turning while tightening the bolts on the pressure-plate to the proper torque specs.

Then we removed the old throw-out bearing, greased the input shaft, slid the new throw-out bearing into place and reattached the shifter fork.

There’s really not much to write about installing the new 3.4L engine that wouldn’t also apply to reinstalling the 3.0L V6. We used a ratchet-strap to adjust the angle of the engine and a floor jack to adjust the angle of the transmission.

After got the engine into position, we bolted-up the engine mounts and started the hardware for the bell-housing support brackets.

The teeth on the 3.0L’s starter won’t mesh properly with the 3.4L flywheel, so one of the mounting holes in the 3.4L starter must be enlarged to 7/16” to adapt it to the 3.0L bellhousing.

Reattaching all of the various vacuum lines, fittings, hoses and cables was very straightforward. We were even able to retain the stock vehicle’s cruis-control.

It’s worth mentioning that this high-pressure power-steering hose was cut to the ideal length and indexed perfectly. Halfway through our installation, we really started to appreciate these little details.

ORS also included a stainless braided flexible clutch line and custom bracket to replace the deteriorating 16 year-old rubber clutch line.

We installed an open-element K&N air filter assembly (intended for V6 Tacoma application) to gain a little more performance and simplify the installation. The K&N kit includes brackets to attach the high-flow cone filter to the factory AFM and we were actually able to use the supplied brackets to support the intake system.

Next we reinstalled the 3.0L radiator, shroud and new-style fan. Then we plumbed the lines and filled the radiator with coolant.


The ORS wiring harness is the heart of the kit. It adapts the entire 3.4L engine harness to the factory wiring harness inside the cab of the truck. Each harness is custom-made to fit customer’s specific vehicle and engine combinations. This is time consuming and labor intensive, but ensures a straightforward and trouble-free installation for those of us that are electrical idiots. All of the plugs and wires in the harness come pre-labeled to avoid any confusion.

We disconnected and carefully pulled the old engine-harness through the firewall grommet and then fed the new harness back through the grommet and into the cab. Then we matched up the correct fittings and the wiring harness installation was almost completed.

The 3.4L ECU is bolted in the same place as the stock ECU using the stock brackets. Plug the ECU into the wring harness and attach the ground wire to the truck body.

ORS supplies a formed sheet-metal battery relocation tray that needs to be welded to the driver side inner fender well. We used a wire wheel to strip the paint away and carefully positioned the battery tray, checking to make sure that it was level. We stitch-welded the battery tray into place using a small 110V Miller MIG welder and .023 solid wire with shielding gas, being mindful not to burn though the thin sheetmetal. Then we laid down a few coats of primer and paint to prevent rust. Note: it’s a good idea to paint the backside of the tray before installing it.

We installed an Optima red top battery for some extra juice and a universal battery tie-down kit from the local auto parts store. Only one main wire from the new harness has to be connected directly to the battery.

All of the gauges will read properly with one exception. The stock tachometer must be modified to recognize the 3.4L ignition signal. We removed the gauge cluster from the dash to access the rear side of it, where we exposed the circuit board.

It is not necessary to remove the tach from the guage cluster (we’ve only shown it this way for clarity). An included 10k ohm resistor is soldered between two contacts is all that is needed to make the tachometer get a correct reading from the engine. The first picture shows the resistor being soldered and the second picture shows the completed job. The instructions are very clear, explaining exactly how to do this. We buttoned up the instrument panel and reinstalled it in the dash.


The 3.4L intake manifold sits about 1 to 1-1/2 inches taller than the 3.0L and in order to reinstall the hood we either had to choose install a 2” body lift or cut a small hole in the hood to clear the engine. We went with option number two.

In order to determine the shape and size of the hole we closed the hood as far as it would go with the new engine and then peeked under the hood to made a few marks with a felt pen. Then we lifted the hood and played connect the dots.

We made the first rough cut about an inch inside of our marked cut-line and slowly enlarged the hole until we had created just enough clearance for the 3.4L intake manifold and throttle body to poke through the hood. We’re eventually planning to make some type of enclosed hood scoop, but we think it looks fine like this too.


With the engine installed, wired and plumbed, the last thing we had to do was re-route the exhaust system. As we mentioned earlier the truck was designed to have the exhaust running down the driver side and the crossover pipe for the 3.4L comes together on the passenger side. There are a few solutions, depending on whether your vehicle has a solid front axle or IFS. It’s possible to use the stock 3.4L crossover and route the exhaust down the passenger’s-side of the vehicle. Another option is to install tubular headers and have a custom exhaust and crossover made. The third option—and the one we chose—is to have a custom crossover made that routes the exhaust down the driver’s-side just like the stock 3.0L. We should be clear that this requires working in a very tight space and should only be trusted to a qualified exhaust expert. We towed this truck straight to Muffler Bob at Cal-State Muffler in Milpitas, CA, who did an outstanding job for us.

Bob bent up a beautiful 2-piece crossover, reusing the factory flanges. He routed the 2.5” exhaust down the driver’s-side, placing the first O2 sensor right before the high-flow catalytic converter and another O2 sensor right after it. From there, the exhaust flows into a Dynomax muffler and out through a turn-down just over the rear axle. The whole exhaust system is routed high and tight, with plenty of support built into a few key brackets.


We were careful to reinstall all of the smog equipment from the 3.4L engine, with the exception of the charcoal-filtered evaporation canister from the ’89 4Runner, which we reused because it fit the engine compartment and we reasoned that it would work just as well as the new one. We didn’t have any problems passing a California smog test (visual inspection and tailpipe sniffer).


After filling up the gas tank and checking all of the fluids, we turned the key and the truck fired right up. It sounded great, but the RPM’s were high. After attaching a vacuum line that we missed, the truck idled nice and steady. No warning lights and all the gauges displayed healthy readings. So-far-so-good. A quick trip around the block confirmed that our new engine was running great.

Since completing the conversion we have logged over 8,000 trouble-free miles, including several road trips through Los Angeles that took us over the long, steep Grapevine and we’ve powered over it repeatedly at 70mph in 5th gear. We also took the truck on a 1,500-mile journey into Baja California consisting of all imaginable types of driving. We have observed fuel economy to the tune of 17-20mpg with 33” BFG Mud-Terrain tires and couldn’t be any happier with the way this project has turned out.

It didn’t take very long for enthusiasts to embrace the powerful 3.4L engine. TRD released a bolt-on supercharger that brings power output to 260hp, as well as a set of tubular exhaust headers and a stainless steel cat-back exhaust system packaged with a Borla muffler. URD also sells a fuel upgrade kit designed to maximize performance of the TRD supercharger. The URD kit couples larger fuel injectors, fuel pump and a fuel controller to custom-tune the fuel maps for each application and improve the lean condition that some TRD supercharged 3.4L engines suffer from.


Parts Included:
• Conversion Wiring Harness
• Power Steering Lines
• Engine Mounts/Brackets
• Radiator Hoses
• Spark Plugs
• Oil pan
• Oil pan liquid sealer
• Oil drain plug w/gasket
• Oil sump assembly
• Oil sump gasket
• Oil dip-stick w/tube, adapter & O-ring
• Oil filter
• Oil pump housing plug
• Tap
• Fuel hoses
• Clutch hydraulic hose & relocation bracket
• Radiator hoses
• Clutch disc & pressure plate
• Clutch release bearing
• Clutch pilot bearing
• Alternator drive belt
• Power steering drive belt
• A/C drive belt
• Battery relocation tray
• 8 gauge battery relocation cable
• Fusible link wire
• 10k ohm resistor
• Large hose clamps
• Small hose clamps
• Hose routing clips
• Wire loom routing clips
• Misc. vacuum hose
• Heater hoses
• Zip ties
• Detailed Instructions

Parts Needed:

• 5VZ-FE longblock
• Exhaust manifolds and crossover pipe (or tubular headers)
• Intake manifold
• Intake plenum with throttle body
• All items on engine related to fuel injection
• Alternator and brackets
• Power steering pump and brackets
• A/C compressor and brackets
• Spark plug wire set
• Cylinder coil packs (3)
• Engine wiring harness
• Igniter assembly
• Intake system- tubing, air box, air filter (or aftermarket intake system)
• Evaporative canister (optional, needed for CA smog)
• Evaporative vapor pressure sensor
• Evaporative vapor pressure VSV
• Evaporative purge VSV
• Starter assembly
• Air flow meter
• Flywheel with mounting hardware
• Oxygen sensors (2)

Reused 3.0L Parts:
• Radiator
• Fan assembly
• Fan clutch assembly
• Engine to bell housing stiffening brackets
• Oil-pressure sender
• Evaporative canister (optional)


Off Road Solutions
Central Foreign Auto Supply
Cal-State Muffler
Trails Less Traveled

This article was originally published in Off-Road Magazine


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