How does CCs affect blade power and torque?

[Craftsman Garage]

I put a predator V twin on my push mower, it sounds like that is what the OP needs

 

[Skippydiesel]

Sorry if this has been mentioned, earlier (several pages would not open for me).

Torque is a measure of the ability to do work - GYM 123 put it very well.

Combustion chamber capacity (cc or cu") is but one component of the engines' ability to deliver torque. Most of the old B&S yellow industrial engines, deliver way more torque for the same capacity (often lower hp) as a modern B&S because of longer conrods/larger flywheel/ possibly higher compression.

The comment "There's no replacement for displacement' is still valid ..." no longer holds good, with the possible exception of drag racing. A small high revving engine, (often high compression) transmitting power through gear box can & does deliver more torque, usually for lower fuel consumption.

The great unwashed (general public) just want something, that makes a noise, boast about the hp. That's why small motors almost always have HP boldly displayed on the side.

 

[Auto Doc's]

140 CC's size engine is approximately 9 HP at 3600 RPM. Most mowers are rated at a top speed of 3600 RPM.

Sounds like you are trying to mow thick tall grass, this engine will not handle that for very long.

Even a 20 HP engine would have a bit of a struggle.

I suggest a bigger mower. Putting a bigger engine on that small chassis will be too much work for no gain, and they don't make blade adapters for bigger engines like that. The push mower decks are light pressed steel in most cases, and a larger engine would destroy the mounting areas in a short time.

Spend the money and look at the commercial grade 36" self-propelled walk behind mowers.

 

[Tiger Small Engine]

140 CC's size engine is approximately 9 HP at 3600 RPM. Most mowers are rated at a top speed of 3600 RPM.

Sounds like you are trying to mow thick tall grass, this engine will not handle that for very long.

Even a 20 HP engine would have a bit of a struggle.

I suggest a bigger mower. Putting a bigger engine on that small chassis will be too much work for no gain, and they don't make blade adapters for bigger engines like that. The push mower decks are light pressed steel in most cases, and a larger engine would destroy the mounting areas in a short time.

Spend the money and look at the commercial grade 36" self-propelled walk behind mowers.

140 CC engine is about 3.5 to 4 horsepower.

 

[Gym123]

Sorry if this has been mentioned, earlier (several pages would not open for me).

Torque is a measure of the ability to do work - GYM 123 put it very well.

Combustion chamber capacity (cc or cu") is but one component of the engines' ability to deliver torque. Most of the old B&S yellow industrial engines, deliver way more torque for the same capacity (often lower hp) as a modern B&S because of longer conrods/larger flywheel/ possibly higher compression.

The comment "There's no replacement for displacement' is still valid ..." no longer holds good, with the possible exception of drag racing. A small high revving engine, (often high compression) transmitting power through gear box can & does deliver more torque, usually for lower fuel consumption.

The great unwashed (general public) just want something, that makes a noise, boast about the hp. That's why small motors almost always have HP boldly displayed on the side.

I haven't seen small engines that were anything but normally aspirated, so displacement still matters. These don't have super/turbochargers or gearboxes that multiply torque in the way cars & trucks do, so crankshaft offset and piston diameter are about the best ways to increase torque.

However, the 'powers that be' in some places want small engines to go away and they're not at the same level of technical development as cars, trucks and other vehicles, so we're stuck slogging through tall grass with 'less than commercial' mowers.

 

[Gym123]

140 CC's size engine is approximately 9 HP at 3600 RPM. Most mowers are rated at a top speed of 3600 RPM.

Sounds like you are trying to mow thick tall grass, this engine will not handle that for very long.

Even a 20 HP engine would have a bit of a struggle.

I suggest a bigger mower. Putting a bigger engine on that small chassis will be too much work for no gain, and they don't make blade adapters for bigger engines like that. The push mower decks are light pressed steel in most cases, and a larger engine would destroy the mounting areas in a short time.

Spend the money and look at the commercial grade 36" self-propelled walk behind mowers.

These are a bit like crotch rocket engines- wind it out and the power is there (measurable) but there's not much torque behind them.

I bought a bagger attachment for the Ariens 42" and the seller had replaced their 46" with a light commercial model because the cost wasn't much higher, but the build quality and performance were better.

As I read about these, it seems that some of the manufacturers are using the Ron White reasoning for giving diamonds to women- "Diamonds, this'll shut her up". Here- give them this, it will work. For awhile.".

 

[StarTech]

The working torque is something that is determine by the ignition timing as if too late at high rpms then the fuel just burns off producing less power even though there is a lot rpms. This the problem using fix timed ignition systems as there is optimum timing point for max torque. And small engines definitely have their limits.

Sometimes it is valve timing or opening up how the engine breathes. I have taken old L head 12.5hp engine and shifted the camshaft by one tooth and therefore shift the torque curve to the higher rpm end making the engine more powerful at the 3600 rpm end. This was on an old Murray rider that was a gutless wonder before the change.

Something we not able to do here is change the grind on camshafts and have variable duration lifters. I took a small 265 V8 and got it where I had plenty of torque and with nearly 23 MPG average with a highway MPG of 32 mpg. It came from the factory rated for 16 mpg highway. I even seen it to get 45 mpg tailgating a 18 wheeler on the interstate.
Now this something I don't recommend anyone doing unless you are in contact with the rig driver.