ohmygahitscoby
Hardcore RCTalk User
Alright, so I see some engines that are like .15, .12, .21, etc. Does this mean that only one of the engine above will fit or can a .21 engine fit if you already have a .12?
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Engine Size?
- Thread starter ohmygahitscoby
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Cupooterluvr
Hardcore RCTalk User
That's the displacement of the engine. I think you can stick a .15 in a .12 space, but .18 is pushing it and .21 isn't going to fit because that's getting into the big block range.
Depends on many factors. As a rule, engines from .12 to .18 are all the same sized block and are interchangeable. .21 to .32 I believe are also the same size. But the block on a .21 is bigger than on a .12 so if you're thinking of putting a big block engine in a small block space, you'll probably need a conversion kit, if they're even available. Or at least be a decent machinist to hack one together in your garage...
ohmygahitscoby
Hardcore RCTalk User
- Thread starter
- #4
Oh okay. I heard that the Mugen MT.12 is a big block, so can I fit a .21 engine into my car?
jetmechG550
RCTalk VIP
No it's not a big block but what car are we talking about?
ohmygahitscoby
Hardcore RCTalk User
- Thread starter
- #6
Oh. It's a Mugen MTX-3.
jetmechG550
RCTalk VIP
small block, .12 if you are racing, .15 for a basher but you can prolly fit an .18 without too much trouble though it's overkill.
ohmygahitscoby
Hardcore RCTalk User
- Thread starter
- #8
I'll stick with my .12 for now. When my .12 dies I'll ask my LHS what could I use that could fit my engine (That they have there).
Technically... big block/small block is all relative to the diameter of the cylinder and the distance of piston movement. If the piston moves less (or the same) distance up and down than the pistons diameter, then I believe it's a big block... Don't quote me on that last part... I can never remember which ratio is BB or SB. I just pretty sure it's directly related to the ratio.
The TRX 2.5, it's diameter is the same as the piston throw, so technically, it's a big block. There are some other small crank case engines that are like that for a specific purpose. I think it adds more torque.
Regardless... typically in RC when a reference is made to small block vs big block, it is a reference to the size of the crank case housing itself.
It's easier to see/understand when you see the enignes side by side.
This is a photo of a 21 big block compared to a 18 small block:
Link to photo
The top engine is a Omega 21, the lower engine is an OS 18 CV-R. Notice how much shorter the crank case is and how much slimmer the area is where the piston goes. The heads are almost the same size. If you looked at them both from the back or front of the engine, you would also see how much fatter the 21 is. This size difference of the crank case is what requires a conversion kit of some sort or a manufactured engine mount. You would also need a different exhaust as most big blocks run a much larger exhaust port.
The TRX 2.5, it's diameter is the same as the piston throw, so technically, it's a big block. There are some other small crank case engines that are like that for a specific purpose. I think it adds more torque.
Regardless... typically in RC when a reference is made to small block vs big block, it is a reference to the size of the crank case housing itself.
It's easier to see/understand when you see the enignes side by side.
This is a photo of a 21 big block compared to a 18 small block:
Link to photo
The top engine is a Omega 21, the lower engine is an OS 18 CV-R. Notice how much shorter the crank case is and how much slimmer the area is where the piston goes. The heads are almost the same size. If you looked at them both from the back or front of the engine, you would also see how much fatter the 21 is. This size difference of the crank case is what requires a conversion kit of some sort or a manufactured engine mount. You would also need a different exhaust as most big blocks run a much larger exhaust port.