Parts/Engines & fuel/Engine parts/O.S. 21TM-T .21 Engine w/T-Maxx Manifold
O.S. 21TM-T .21 Engine w/T-Maxx Manifold
O.S.

O.S. 21TM-T .21 Engine w/T-Maxx Manifold

Part # OSM122404.5(8)
Where to buy
$269.99
AMain Hobbies
Seen Oct 12, 2026
$269.99Buy
Prices are as last seen at the store; stock is not tracked.

About this part

The O.S. 21TM-T .21 Engine w/T-Maxx Manifold is a great option for those looking to get a little more out of their Traxxas T-Maxx or. A LC3 glow plug is used with this engine for improved power, better fuel economy and durability. The carburetor used offers easy handling as well as high end performance. 

Features:
  • Great option for the Traxxas T-Maxx 2.5 and 3.3
  • Uses a LC3 glow plug for outstanding performance
  • Carburetor offers easy handling and top end performance
  • Includes Traxxas style manifold
Specifications:
RPM Range: 3,000 - 35,000 rpm
Recommended Fuel: 10-30% nitro content, 20% for break-in
Width: 1.5 in (39 mm) at mounting tabs
Carb Type: 11K three needle slide valve
Height: 4 in (101 mm)
Stroke: 0.590 in (15 mm)
Plug Type: LC3
Length: 2.1 in (53.6 mm) from backplate to drive hub
Displacement: 0.213 cu in (3.49 cc)
Bore: 0.669 in (17 mm)
Total Weight: 8.57 oz (243 g)
Type: 2-stroke glow powered 1/8 scale monster truck engine
Crankshaft Type: Threaded
Crankshaft Threads: M7x1
HP: 1.77 HP (1.8 PS) @ 29,000 rpm

Includes:
  • (1) O.S. 21TM-T .21 Engine
  • (1) LC3 Glow Plug
  • (1) 2.5 Manifold
  • (1) Manual
CA Residents Prop 65 Warning WARNING: This product can expose you to chemicals including Di(2-ethylhexyl)phthalate (DEHP), which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov Details...

Reviews4.5 · 8 reviews

Brandon LieferVerified owneron O.S. 21TM-T .21 Engine w/T-Maxx Manifold

Quality is great however you will need to buy a different air cleaner setup to put in a T Maxx nitro 3.3.Everything was easy swapping out the stock 3.3 for this little powerhouse except a couple small things. 1) you will need a dremmel to grind a little bit off the base if you want to hook up the factory rpm sensor . 2)you will need a new air cleaner setup or a reducer as the carb hole is bigger than factory (I used the os 203 kit on one and a losi m8 on the other ) and they both worked equally as well ) 3)It was hard for me to tune because id never tuned one before …I ran 4 tanks for break in then it took me another 4 tanks to get a tune I was semi satisfied with and another 2-3 to get it where i felt it was really dialed in! 4) you will need a GOOD wheelie Bar as this little Basxxxd has some serious power and or responsive characteristics compared to stock! I can’t keep the front down it wheelies at 1/3 throttle and has enough axx to flip this dude on accident frequently!!! 5) Tell your significant other to be prepared because it will create a definite chubby!

4 found this helpful
Barry BrannonVerified owneron O.S. 21TM-T .21 Engine w/T-Maxx Manifold

Best upgrade I did on my T-Maxx. Tuning is straight forward. Idles great. Low end torque is insane. Would recommend to anybody and purchase again.

3 found this helpful
Andries Buskenson O.S. 21TM-T .21 Engine w/T-Maxx Manifold

Love love love my OS TM engines!! Fantastic small blocks that scream and have way more torque then any other small block ever made

3 found this helpful
Michael AnderlieVerified owneron O.S. 21TM-T .21 Engine w/T-Maxx Manifold

I purchased this engine for my Tmaxx 3.3 and these OS .21 TM engine is the best .21 size engine you can buy and install and run in Tmaxx’s. Its starts and idle very easy i followed the break in using Adam Drake method. Since the instructions dont give whole lot information. But once that done i tuned the engine and wheelies every time. Its built so well and all the parts seemed to be machined rather then cast which is nice. Only small complaint is the back plate uses Phillips screws instead of Allen hex but other then that This OS engine is the way to go for Any Tmaxx.

2 found this helpful
Sebastian NieruczkowVerified owneron O.S. 21TM-T .21 Engine w/T-Maxx Manifold

The most amazing upgrade for the t-maxx. Direct drop for real , and make the t-maxx well tuned a weele king! 100% recomendable! make nitro great again!

1 found this helpful
What reviewers say

Reviewers generally rate this O.S. 21TM-T .21 engine highly for the T-Maxx, praising its torque, idle, and build quality, and noting that installation was largely a direct swap. Several reviewers mention needing a different air cleaner or reducer because the carburettor bore is larger than stock, and one needed a small grind for the RPM sensor. Tuning took some owners many tanks, particularly those new to tuning. Phillips-head back plate screws are mentioned as a minor complaint by one reviewer and as a problem by another, who reported stripping them and being unable to use the engine. Most reviews are five-star; the single one-star review is the main dissent.

  • + Strong low-end torque
  • + Good idle
  • + Machined parts and solid build
  • + Direct swap into T-Maxx
  • − Needs different air cleaner or reducer
  • − Tuning takes many tanks
  • − Phillips back plate screws
  • − Screws can strip easily
Summary generated from the reviews above.

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