Small Block vs Big Block Speed Difference? What is Better?

SquidBonez

Member
It seems like every Honda clone powered machine on YouTube (be it go kart, mini bike, or mini buggy) runs a small block if they want to really go fast. At least from what I've seen online - by and large - built small blocks are faster than most big blocks. There are tons of videos of people hitting 70+ on small block mini bikes, but very few videos on people hitting high speeds on big blocks. Does anyone here have experience with big block engines? How do they compare to small blocks on the old "butt-dyno"? I would think that the extra power and torque from big blocks would make it no contest - even with the added weight. I know speed is overall determined by gear ratio & RPM, and that big blocks don't rev as high, but you can gear a big block more aggressively than a small block thanks to the extra power & torque they provide. Torque converter options are also more limited for big blocks (there's no "Juggernaut 30 series" equivalent for big block engines...maybe the 780?).

Ultimately, I'm just trying to decide if I should go big block or small block on a lightweight mini buggy I'm building. I currently have the parts to build a Stage 2 Predator 212 coming in, but I'm just wondering if I should stick with a small block or pay the extra money and upgrade to a big block. I'm looking for something that will do well at high speed (rally-style) driving on dirt roads and grass fields. Would it be better to use a lighter, less powerful, but higher revving small block, or a heavier, more powerful, but lower revving big block? I already have a Juggernaut torque converter for my 212, but if I go big block I will change out to a 40 series.
 
Not exactly sure what sort of a mini you are building but if you have the space, a larger motor in mild tune would certainly last longer. Why not something out of an atv dirt bike or snowmobile?
 
Not exactly sure what sort of a mini you are building but if you have the space, a larger motor in mild tune would certainly last longer. Why not something out of an atv dirt bike or snowmobile?
Well I'd be getting billet parts regardless of which motor I use (not taking the chance). And I'd rather use a clone motor in the meantime simply because I know how to work on them and where to get parts for them. Like I said, I already have the parts for a Stage 2 Predator 212 that I'll be putting on a "test mule" kart to see how it performs. If I like it I'll swap it over when I build the buggy. If not I'll go big block. Just hope a Comet 40 series handles a modified big block as well as the Juggernaut handles the modified small block.
 
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You will be limited by that series 40 TC. Some built small blocks will make upwards of 30hp. Some built big blocks will do that and more. The series 40 is rated up to 18 HP. You can build the 212 up to that but it will cost a little bit for the billet parts but not as expensive as building a flathead or Animal. It will take a good bit of work to get 18 out of that engine but it definitely can be done. I’d probably that route. Another option is to buy a 3” bore Tillotson clone block and build that with billet parts. Big bore small block.
 
Adapt one off a snowmobile .
I could out run my buddies big block sometimes with my 327 .
It was maxed out were the big block was not struggling .
Heavy off road vehicle I would just go big block .
 
They do pretty well on snowmobiles. And since this would be an off-road kart, I would absolutely be going with one.
Jack shaft with the disc clutch on the Jack shaft.
Snowmobiles have a clutch, unlike a yard kart torque converter
 
Jack shaft with the disc clutch on the Jack shaft.
Snowmobiles have a clutch, unlike a yard kart torque converter
Go kart "torque converters" are just simple CVT transmissions. Snowmobiles use CVTs as well. What they often call "clutches" are just drive/driven pulleys. Using a jackshaft with a clutch disk still wouldn't be better than a Juggernaut CVT, because the whole point of a CVT is to give you a range of gear ratios. A jackshaft/clutch would still give you just one fixed ratio.
 
It seems like every Honda clone powered machine on YouTube (be it go kart, mini bike, or mini buggy) runs a small block if they want to really go fast. At least from what I've seen online - by and large - built small blocks are faster than most big blocks. There are tons of videos of people hitting 70+ on small block mini bikes, but very few videos on people hitting high speeds on big blocks. Does anyone here have experience with big block engines? How do they compare to small blocks on the old "butt-dyno"? I would think that the extra power and torque from big blocks would make it no contest - even with the added weight. I know speed is overall determined by gear ratio & RPM, and that big blocks don't rev as high, but you can gear a big block more aggressively than a small block thanks to the extra power & torque they provide. Torque converter options are also more limited for big blocks (there's no "Juggernaut 30 series" equivalent for big block engines...maybe the 780?).

Ultimately, I'm just trying to decide if I should go big block or small block on a lightweight mini buggy I'm building. I currently have the parts to build a Stage 2 Predator 212 coming in, but I'm just wondering if I should stick with a small block or pay the extra money and upgrade to a big block. I'm looking for something that will do well at high speed (rally-style) driving on dirt roads and grass fields. Would it be better to use a lighter, less powerful, but higher revving small block, or a heavier, more powerful, but lower revving big block? I already have a Juggernaut torque converter for my 212, but if I go big block I will change out to a 40 series.
in my opinion I'd go with the big block. less mods necessary for equal or better performance. more torque=more fun
I may be biased since I have a built tecumseh star motor
 
First down side I see is a Predator 420 costs about 3 times as much as a 212 out of the box and performance parts run about double that of small block parts. Then add on the fact that it weighs double also. A 301 Predator might be an option but those parts run in the same price range as 420 parts. I seem to recall someone posting that they had problems keeping big blocks together when racing but don't quote me on that.
 
I've seen quite a few Kawasaki Ninja 250 engines on eBay in the 500$ range. The put out 29.9 HP from the factory. The down side is they're water cooled and I don't know how much of hassle it would be to set up the carbs, electronics, and what not to get everything working.
 
Go kart "torque converters" are just simple CVT transmissions. Snowmobiles use CVTs as well. What they often call "clutches" are just drive/driven pulleys. Using a jackshaft with a clutch disk still wouldn't be better than a Juggernaut CVT, because the whole point of a CVT is to give you a range of gear ratios. A jackshaft/clutch would still give you just one fixed ratio.
Just because the torque converter doesn't lock you into a fixed ratio does not mean it's speed potential is infinite. There is a lot of slippage and although eventually you may get locked into its potential output
the fact is that it
does not mean it is fast. A clutch locks in without much slippage then is limited to how much HP the motor makes and gearing decides the speed. A lot is lost in the nearly constant slippage the torque converter causes. You have to remember you are in a go kart racing forum where 95% of us race go karts only and only know one way of doing things. If torque converters were fast and efficient we would all use them. We do not.
 
There is a guy on youtube who has small blocks but they are bored to a big block and he does a bunch of supports on the motor and welds all over on them. He makes the blocks very strong and puts massive pistons in those little blocks.
 
Just because the torque converter doesn't lock you into a fixed ratio does not mean it's speed potential is infinite. There is a lot of slippage and although eventually you may get locked into its potential output
the fact is that it
does not mean it is fast. A clutch locks in without much slippage then is limited to how much HP the motor makes and gearing decides the speed. A lot is lost in the nearly constant slippage the torque converter causes. You have to remember you are in a go kart racing forum where 95% of us race go karts only and only know one way of doing things. If torque converters were fast and efficient we would all use them. We do not.
I get that a clutch is way more efficient on top end (where racing karts spend most of their time), but this thread was created with the intention of trying to find an engine for an off road kart/mini-buggy, where a CVT is required.
 
Really it comes down to how much your creation will weigh more than anything else. And you really would be further ahead waiting on buying all billet parts. What is being marketed as "Stage 2" really isn't much as far as performance parts go and certainly doesnt warrant the cost of a pile of billet parts, other than the connecting rod. If it's heavy just run a big block. Youll be burning up belts trying to get a heavier vehicle rolling with a small block. As far as building something fast enough to be successfully ran like a rally machine the stock big block with improvements as you can afford them would really be the way to roll.
 
Really it comes down to how much your creation will weigh more than anything else. And you really would be further ahead waiting on buying all billet parts. What is being marketed as "Stage 2" really isn't much as far as performance parts go and certainly doesnt warrant the cost of a pile of billet parts, other than the connecting rod. If it's heavy just run a big block. Youll be burning up belts trying to get a heavier vehicle rolling with a small block. As far as building something fast enough to be successfully ran like a rally machine the stock big block with improvements as you can afford them would really be the way to roll.
Most likely well under 400 pounds. Hopefully. Probably closer to 300 actually.
 
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