How does CCs affect blade power and torque?

[Piros1]

I think you have had enough answers regarding cutting your grass, you let it get to long, etc so I’m not going there. Also as stated you could install a much larger engine to do the job but your deck won’t handle it. I think all this is covered. But you asked about more CC’s. CC’s is metric and stands for cubic centimeters kind of like CI (cubic inches) in US terms. The more CC’s your engine is the larger the displacement kind of like a Chevy 327 compared to a 427. So in theory everything being equal a 170 CC engine should have more power than a 140 as would 220 CC have more power than a 170. The issue becomes mounting the engine to your deck and the length of the shaft protruding through your deck and will your blade and hardware mount to the larger engine. By the time you are done you may be money ahead to find a good used mower to your liking. It is doable provided your hardware and the engine are a match up. I don’t think it will solve your issue with your existing mower and conditions. The deck design of any mower has a lot to do with how the grass is discharging out the shoot. I do think that if you are planning to swap your 140CC engine for a 170CC engine you will notice lift or no difference and I feel personally you would be wasting your time and money.
I wish you the best and good luck on your decision.

 

[jimbir]

I want to get a mower engine and swap onto my little 21" 140cc Craftsman. I let my yard get way too high and went to mow it, but it was barely able to handle it, and I had to push it 2ft, backtrack 3, then go forward slowly.

Anyway, I was looking at a new mower, but they're all 150 or 170 or 163 cc (for the well rated ones. There's several 200ish cc ones for outrageous money, or with like 2 stars.

So, I'm curious. How much does engine CC actually do? Will I notice a difference between my 140cc and a 150? What about 163 or 170? Where would I need to go to buy a bigger engine that I could just swap onto the mower?

Depending on the blade diameter, the most common engine CC ratings are 159 and 196 for walk behind mowers. These numbers divided by 15 gives you a rough idea of its horse power at maximum rpm. (Back in the old days, this was what was on the engines label telling you what it was rated at.) This answers your question in the simplest terms. If you care to read below, you’ll find the rest of the story below:

What you need to efficiently cut grass (work) is torque and this is dependent on engine rpm. The higher the rpm, the higher the torque the maximum level of which is also dependent on the number of CC’s. Lawnmower engines typically are regulated to run around 1500 rpm by the governor at no load (it’s not doing any work,). At this speed the engine is producing about 40% of its rated torque. When you start to cut grass (load), the engine begins to slow down. The governor senses this and opens the throttle causing the engine rpm and the torque to increase the necessary amount to cut the grass. (You will notice an increase in engine noise.) It will open the throttle until the engine is producing it’s maximum rated torque. Any significant increase in the load after this will cause the engine to stall.

Indecently. A 21” mower with a 140CC, Though that’s a little light, should be able to cut grass 4 to 5” tall. If your mower has a lot of miles on it, I’d take the cover off and make sure the governor linkage is free to move.

I welcome that If anyone notices any significant mistakes in the above to correct me.

 

[millardkl@hotmail.com]

I want to get a mower engine and swap onto my little 21" 140cc Craftsman. I let my yard get way too high and went to mow it, but it was barely able to handle it, and I had to push it 2ft, backtrack 3, then go forward slowly.

Anyway, I was looking at a new mower, but they're all 150 or 170 or 163 cc (for the well rated ones. There's several 200ish cc ones for outrageous money, or with like 2 stars.

So, I'm curious. How much does engine CC actually do? Will I notice a difference between my 140cc and a 150? What about 163 or 170? Where would I need to go to buy a bigger engine that I could just swap onto the mower?

Power just may not be the best answer. Deck design and blade efficiency may make a big difference. We also don't know if the present engine is working at its optimum.

 

[Chuckers]

My yard is a swamp. It hasn't rained for 3 days and there's still standing water...

Sounds like you need to take the money you want to spend on an engine/mower and put it toward fixing that drainage issue instead.

 

[aussielawny]

Put a B&S 850 engine on it

 

[7394]

Put a B&S 850 engine on it

Yea that's the ticket...

 

[DinosaurMike]

Sounds like you need to take the money you want to spend on an engine/mower and put it toward fixing that drainage issue instead.

Chuckers has the best post in all 6 pages.
Forget about engine HP and Torque. I don't recall if you have a push or self-propelled mower. My discussion is for a push mower. You need to raise the deck to cut tall grass. The top of the deck should be equal to or lower than the grass height. I can think of two options. 1. You could try figuring out a way to install larger wheels. You might need longer axles to do this because the cutting area of the deck is wider than the wheels area. 2. Here is an idea way outside the box which is serious even though it sounds ridiculous. Figure out how to add outdoor plate style casters to bolt-on wood or metal crosspieces for high grass. Just remove the cross piece assemblies for regular mowing.
Next best choice is a wheeled string trimmer with a high-lift kit. Again, serious although it sounds ludicrous.
One of my friends has a problem with standing water after winter snows melt or after periods of lots of rain. He is waiting for me to design/build a pontoon or hovercraft tractor.

 

[4getgto]

The guy is trying to mow a lawn that's like a swamp and standing water. Ain't a mower out there to this regardless of torque and horsepower. Either let it turn into a marsh and enjoy the frogs or wait till it dries out..

 

[Little Fish]

First thing, make sure your blades are sharp. Not like a knife edge, but close. And you want the tip as close to a 90 degree edge as you can get it. Not rounded or curved, that will just push the grass aside. The tip cuts 99% of the grass. Considering how fast the blade spins, the mower moves hundredths of an inch from the time one tip is in front of the mower thill the opposing tip is in front. Then balance the blade. This is just as important as sharpening the blade. An out of balance blade will not spin as fast, and will bog down much easier.

I did that. You're right that the tip cuts most of the grass initially, but then the other parts come into play for mulching and throwing it into the bag.
Even after sharpening, it was not very good. Definitely improved, but not great.

Torque and hp typically go hand in hand but you’re definitely looking for more torque. Hp=faster blade but not necessarily more power Torque=more powerful blade. Or Hp is how fast you hit the wall, Torque us how far you push the wall. Look for an engine with the most torque that will physically fit and work. It’ll help with what you’re looking to do. Now whether you’re deck will handle it in the long term is hard to say. Keep mounting bolts tightand watch for tearing and warping on the deck. Most likely you’ll be fine with the small amounts we’re talking. Shoot for something in the 8ftlb range and it’ll help for sure.

Thanks! Any recommendations on where to find one? And are all vertical shaft engine shafts the same (so I could just swap the B&S to whatever I find without adapters)?

 

[Chiefwebb]

I'm late to this discussion but wanted to add my 2-cents about replacement engines. About 30 years ago I had a small engine repair shop. I found that the vertical shaft B&S engines that Craftsman placed on their push mower decks were unique due to PTO shaft length and blade mounting. They forced most customers to have to get their replacement engine from Sears/Craftsman. Briggs & Stratton would not sell the engine to even repair shops. So if you are planning to replace your engine on a Craftsman deck be mindfully of that.