Overbored Throttle Body and Intake Manifold

22RE | 3.0 V6 | FAQ

22RE Kit

Feb 25/02

Anyone who has driven a Toyota 4x4 with a 22RE knows that it's very underpowered; this is especially noticeable at highway speeds when heading up a steep grade like the Coquihalla Hwy or Hwy 97 west out of Kelowna. Other areas where a power boost is desirable is for passing and while towing a trailer. On the trail, more power is nice when crawling up a steep climb, and for spinning the tires in mud to clean out the voids. Personally, I really notice the lack of power when I'm fully loaded for a week's worth of camping, complete with tools, spare parts, and a navigator, or when I'm climbing a hill while towing my ATV and trailer.

One popular method of improving engine performance is to increase air flow, through the use of a low-restriction air cleaner and an overbored throttle body. Overbored throttle bodies are available from a few different sources in the USA, for approximately US$250.00. Basically, the stock 55mm bore is increased 3mm to 58mm, allowing increased air flow at open throttle. This increased air flow is necessary to allow your other engine mods to perform at peak efficiency. While the idea is sound, the intake manifold bore is still only 55mm, so performance gains cannot be fully realized. Mark Ergetowski of Metal Action in New Westminster, BC, has the solution we've all been looking for, a 3mm-overbored throttle body and a 3mm-overbored intake manifold.

Overbored throttle body and intake manifold assembly Throttle body bore Throttle valve open

Mark bores out the throttle body to 58mm, then replaces the throttle valve with a larger unit to properly seal against the larger diameter bore. He flattens the throttle valve (a.k.a. the butterfly valve) pivot, which further reduces the restriction and provides additional air flow. He then bores out the intake manifold to 58mm, so that the increased air flow is not restricted by the stock 55mm intake manifold bore.

We installed one of his setups in my truck, a 1985 Xtra-cab with a 22RE that was rebuilt 10 months ago, cylinders bored .030" over. Other mods I've done include a Shadbolt M1144 cam, a K&N FilterCharger air cleaner (drop-in element), and 2.25" cat-back exhaust with turbo muffler. I have a factory exhaust manifold and stock catalytic converter.

The first order of business was to see how the truck performed in it's present form. Since I had a 5-speed manual tranny, we measured accelleration times in 3rd gear from 60km/h to 80km/h; this would eliminate any variables due to shifting. We did three passes; the results were 6.76 seconds, 6.87 seconds, and 6.83 seconds; this averages out to 6.82 seconds.

We then pulled the truck into Mark's garage and re & re'd the throttle body and intake manifold; removal of the old setup took 29 minutes, and installation of the new setup took 50 minutes. We spent another approximately 30 minutes setting up the throttle valve position, TPS (throttle position sensor), and idle. These times included pauses for photos and chatting, and the entire operation was performed with standard hand tools.

Stock throttle body and intake manifold Throttle body and intake manifold removed Overbored throttle body and intake manifold installed

Back out to our test track; we did three passes with the following results: 6.40 seconds, 6.40 seconds, and 6.27 seconds. This averages out to 6.36 seconds, or a 6.8% improvement. Apparently it takes about 5-10 hours of driving for the CPU to reprogram itself, so we'll repeat this test in a few days.

During the next few days, I noticed that when I was in traffic, launching off the line was quicker. The throttle response and acceleration had improved, and the engine just seemed to pull a bit better. When I took the truck out onto the highway; I felt a definite improvement between 3000-4000 RPM, when passing cars on an uphill grade in 4th gear.

A few days later, we returned to our test track for a re-test; we did several passes, with the following results: 6.10 seconds, 6.15 seconds, 6.03 seconds, and 5.98 seconds. This averages out to 6.07 seconds, or an 11% increase in performance over stock. Not bad for less than two hours work!

If you are looking for more power for your 22RE, I highly recommend this setup in combination with the afore-mentioned mods (air cleaner, cam, and exhaust). While you have the intake off, you may also want to port-match it; we didn't do this as we were testing the overbore only.

3.0 V6 Kit

July 16/02

Mark now has a kit available for the 3.0 litre V6.

The 3.0 kit is similar to the 22RE kit; it includes both the throttle body and the upper intake manifold. The factory bore is 60mm; the new throttle body is bored out to 63mm, and the intake manifold's tapered "snout" is machined to match.

All work has been done on a CNC machine, with tolerances far exceeding OEM specs. The flap has been made out of aerospace aluminum alloy, and the throttle-body shaft has been ground to maximize airflow.

Overbored throttle body Overbored upper intake manifold Stock 3.0 litre V6 Lots of hoses to disconnect

We installed a kit into Norm's 1991 4Runner; stock except for a K&N drop-in replacement filter. As with the 22RE test, we did six passes from 60km/h to 80km/h to eliminate any variances due to shifting; the 4Runner averaged 4.73 seconds.

We pulled the 4Runner into the shop and swapped in the new kit; this actually took a few hours because the overbored kit was for a 1990 engine, and Norm's 1991 had a couple different coolant or vaccuum fittings, and we had to make all the hoses match up. So when you order your V6 kit, you'll have to supply Mark with the exact date of manufacture or you might end up tapping a hole or two, and changing some fittings. Nothing difficult, mind you, but it will take time and you'll have to pick up the fittings if you don't have them on hand.

We then took it back out to our test track; we did another six passes averaging 4.20 seconds, which works out to a 12.6% improvement. Norm had a big grin on his face! After a few days, we'll retest to see if the computer has allowed any further improvement.

Frequently-Asked Questions

Mark understandably gets a lot of questions about this setup, so to help him out I've posted his FAQ here. If the answers you seek are not found below, email Mark and he'll be happy to help you out.

For pricing or additional information, you can contact Mark at
Metal Action; phone (604) 519-0676, or email .

Be sure to tell him you heard about it here!

What's the reason for the modification?
The modification increases the venturi diameter by 3mm; this increases the air flow through the venturi, thus increasing the charge in the cylinders. More mixture means more power.

What kind of performance improvement can I expect?
That depends on the condition of the engine (mileage, maintenance, etc.). For an engine in good condition, the expected power increase is about 10%.

What is the increase of the venturi cross-section area?
For the 22RE kit, the venturi itself is 11.2% larger, and there's an additional .85% gained by grinding off additional material from the butterfly shaft, so the total increase of cross-section area is about 12%.

For the 3.0 V6 kit, the venturi itself is 10.2% larger, plus 0.3% from flattening the butterfly shaft, for a total increase of cross-section area of 10.5%.

Does the power/torque curve change after installing?
There are no dyno results available at this time; however my personal feeling is that both torque and power curves remain the same in respect to their shape, but the respective values after installing the kit are noticeably higher throughout the entire RPM range.

Are there any other restrictions in the intake system?
This system includes modified throttle body AND intake manifold. BOTH are overbored 3mm, thus ensuring an optimal and unrestricted airflow into the engine. However, a high-flow air filter insert is recommended because of the higher flow ratio achieved.

Can I purchase just the throttle body?
The throttle body and the upper intake manifold have BOTH been modified; they have been designed and tested as a set. They are not available separately because mounting a modified throttle body on a stock manifold will NOT increase the engine power as expected.

Are both pre-1989 and 1989+ 22RE intake styles available? What's the difference?
Both styles are available. The pre-1989 style is angled down at the front, while the 1989-and-later style is straight, or horizontal; this accompanied a throttle linkage change.

Pre-1989 intake 1989 and later intake
Left: Pre-1989 intake          Right: 1989+ intake

Will my gas mileage be affected?
That depends on your driving pattern. Just like on a non-modified vehicle, a heavy foot will mean a large bill at the gas pump. Remember that the maximum power gain is only at full throttle (ie. hills, passing, etc.). Moderate use of the gas pedal will keep the gas consumption down even with this kit installed.

Do I need to use a higher-octane gas?
No; we used standard 87-octane pump gas for all tests.

What is the life expectancy of the kit?
The life expectancy is the same as the factory setup. The modifications are done to very high tolerances, using aerospace-quality materials.

How difficult is it to install?
It's quite easy for a mechanically-inclined person with basic hand tools. Disconnect the hoses and connectors, unbolt the old throttle body and intake, install the new throttle body and intake, reconnect the hoses and connectors, and set up the throttle valve position, TPS (throttle position sensor), and idle.

Can I use my stock fuel pump and injectors?
Yes; no other mods are required.

Will I still pass AirCare with this setup?
Yes; this mod will not affect your AirCare readings.

Do I need to adjust my mass air sensor?

I've heard of a 4mm-overbore; do you do this?
No, a 4mm-overbore is pushing the limits of the casting. Some throttle bodies can handle it, others cannot; you won't know if your throttle body wall is too thin until it develops a crack one day.

If you use silicone to form gaskets, it must be labelled "sensor safe", or you can damage your oxygen sensor.

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