# check out this lawn mower engine (kohler engine)

Discussion in 'General Experimental Aviation Questions' started by oldcrow, Jan 9, 2020.

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1. Jan 14, 2020

### litespeed

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I don't really see 70 hp on a big block as a big ask especially if machine can do with a much lower amount.

50 % would probably be fine for cruising around and bigger power would be short periods. If cooled well it should not be a issue, add some quality internals, a bigger sump volume,a quality light weight motorbike oil cooler , a good flow job and balance, quality carbs- two not one. Add higher comp pistons, springs and retainers, coat the head internals and piston crown for heat, pick a cam to suit your rev range and torque curve. Make a quality header set and it should be able to make the 70 hp and not be a worry for a aircraft. And add a quality (not cheap) ignition system that makes lovely fat sparks.

70hp a litre max is not real big, in fact no more than a stock Moto Guzzi made. At 60 % its making 42hp at 70 % 49hp. So the 49hp with a quality build and parts should be fine as long as the heat is managed. That is more than a big block is max power approx but I expect it would actually spend time doing a lot less in a aircraft with Duncan.

If 50hp was Ok, then thats say 35hp cruise, so a hot one will hardly be working its guts out. A well modded one should be smoother, use a bit less fuel for a given power, run cooler and be much more reliable.

Would you scream around at max power? not likely. At reasonable loads and revs when replacing a normal but heavier version with a light , smooth and efficient version with more usable power- it should be a good thing.

The only downside is labour and parts costs to do it right, but still that is not excessive.

If it cant cruise at 40 hp all day, I would be very surprised.

2. Jan 14, 2020

### pictsidhe

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The hot version of the big twin was 50hp. That conversion was done by a competent engineer. i have little doubt that he could have squeezed more power out of it, if he thought it was a good idea. I have yet to hear of a reliable aircraft conversion running around double the stock power. There are, however, plenty of people who haven't tried it who are saying that it shouldn't be a problem...

3. Jan 16, 2020

### litespeed

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Touche....

4. Jan 22, 2020

### D_limiter

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The DA-11 is a pretty little plane, emphasis on little. Useful load is only 200lb, which is not useful for my 200lb plus carcass.

I’m fascinated by the v-twin conversions, because they are mass market engines with modern engineering at a reasonable price. I would love to see a working conversion on a aircraft. Are there any, or is it still premature?

5. Jan 22, 2020

### Jay Dub

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Kevin Armstrong in the UK put about 160 hours on a Japanese made Briggs vanguard 627.He didn't use a reinforced cam and it broke. He put in a specially made cam (and recommends a reinforced one after his forced landing), changed rods and pistons, HD valve springs, SS valves, etc. He wasn't well received here on hba but I've contacted him and he has a lot of development information. He has many YouTube videos under his name. He is now using a liquid cooled Chinese atv engine and that is working well. I respect him highly and can't understand why he wasn't well received here.

A guy named Kleber in Brazil made a few 627s using info from Kevin but he doesn't change much of the internals other than HD valve springs, dual mikuni carbs, and a tuned exhaust. Both Kevin and Kleber estimate 35 to 39 HP with their respective mods. They say they burn around 1.2 to 1.5 gph cruising around.

Parazoom also uses the 627 on their machines. It's being done. It seems many here will tell you why it can't be done reliably but people like Kevin, Kleber, and Parazoom are doing it and sharing weak areas to be aware of. It's called experimental aviation for a reason. If you want certified parts, then fly certified airplanes. If you're willing to experiment with the possibility of a failure, then experimental aviation might be for you.

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6. Jan 22, 2020

### litespeed

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despite the naysayers above, who happily condemn any suggestions of the ability to reliably use a modded version.

Well a 627 cc 23hp engine with slight mods for reliability is at 39 hp making Guess how much extra?

70%, just like I said a big block one, could do with even better mods for flow, cooling , stronger and better balanced parts can be done.

It is not rocket science, but simple mechanical engineering.

And a big block is not likely to be running around at anything like more than 65=70 % load for anything than a few minutes.

The facts in the air tend to indicate it is not a huge problem.

7. Jan 22, 2020

### lr27

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I think the Columban Lucille usually uses a converted Briggs, and I've seen ads from some company in Europe that sells them already converted. The engine in the Da-9, as I recall, has only 21 up. V-twins get a lot bigger than that.

8. Jan 22, 2020

### Vigilant1

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Yes, these engines are in common use, and getting more common. The search function here at HBA will produce many examples of folks discussing these engines, doing the work to convert them, and some accounts of folks who have flown them. The most common planes that use these engines in direct drive mode are the MC30 Luciole and the Minisport SD-1. Slower draggier aircraft (ultralights, trikes, etc) typically use these engines with a PSRU.

HBA member TiPi is documenting the rationale behind his engine choice for his SD-1 and the steps he's taking to convert the B&S 810 to run heads down. More here: https://www.homebuiltairplanes.com/forums/threads/b-s-49-series-810cm3-49ci-tipis-conversion-for-aircraft-use.32368/ And here's a thread with questions/answers about his project: https://www.homebuiltairplanes.com/...49ci-for-aircraft-use-tipis-q-a-thread.32382/
Here's a post with a slideshow of the SD-1 conversion of a B&S 810cc engine
About the 22 HP Predator engine from Harbor Freight in the US:https://www.homebuiltairplanes.com/...reight-engine-evaluation-other-v-tiwns.21130/
Kevin posted here under username "Factory-Fit," a search for his posts will be useful to those interested in using these engines with a PSRU. My post here gave some info on his Vanguard 627cc conversion and a link to a video he made. He is a big fan of Ace Redrives, that is for sure. He posted later in the same thread and I think a lot of good information was shared. Others can judge if he was "well received."

Too often when folks quote HP numbers they don't say whether the engine can make that power continuously. Of course these engines can make 1 HP/cu inch and more, the racing mowers do that. Make the mechanical mods and run them at high RPM--not a mystery at all. But at that HP, they can't shed the heat as fast as it is being made, and so the heads get hot, and bad things happen soon thereafter (just like any air cooled engine). Valley Engineering sold their Big Block with HPs up to 50, but they were honest in saying the continuous HP they would make was 32. Maybe some more careful attention to airflow/baffling would allow a few more HP from a big block, but anyone claiming they can make 50 HP for 20 minutes straight, and have the engine last for a few hundred hours---well...

Last edited: Jan 22, 2020
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9. Jan 22, 2020

### lr27

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I think I read someplace that a guy had a way to extend cooling fins. Some kind of aluminum brazing? I'm skeptical, but it would be nice.

10. Jan 23, 2020

### Vigilant1

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Bob Hoover (no, not THAT Bob Hoover) used a newly available (at the time) welding rod to make his "fat fin" VW modification. He claimed that it did improve the ability of the heads to shed heat. It might be useful for these industrial engine heads, the stock fin spacing is quite wide (probably to allow debris to pass through without clogging them, at least not right away).
But none of this is going to be magic. Lycoming, Continental, VW, stock B&S engines--all of these air cooled NA 4 stroke engines have remarkably similar cc/continuous HP ratios despite a lot of investment and a lot of commercial incentive to up the HP if it could be done simply and reliably.

Last edited: Jan 23, 2020
11. Jan 23, 2020

### lr27

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The Briggs in its native habitat is fan cooled, so maybe it doesn't need the fins. OTOH, that habitat,is dusty.

I thought of the right Bob Hoover right away, and then you confused me.

12. Jan 23, 2020

### pictsidhe

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Bob hoover played with welding additional fins on VWs. If you want to achieve VW power, you will need VW size fins.

13. Jan 23, 2020

### Jay Dub

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According to Kevin Armstrong, the vanguard 627 using the forced air cooling never had a cooling issue. His machine used high comp pistons, different valve train, larger carb, etc and still his cht temps stayed good. Free air cooling could possibly be different though.

You must keep in mind, these engines are made to run @ 3600 rpms (some up to 4000 rpms) in stationary environments with the full load of a pump or generator, with dirt and grass clippings stuck in the fins and still not overheat. That's what they are designed to do day after day. Automotive engines are not.

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14. Jan 23, 2020

### blane.c

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Last I checked you could get the 830cc engines with EFI for around $1700 each and some carbureted versions are just under$1000 . The less expensive carbureted versions of this engine are being modified in for example the SD-1 ( https://www.sdplanes.com/ ) and some people in this forum (HBA) are either documenting a conversion or planning/dreaming of using one or more of them in a experimental design. Depending on who's doing the work or the planning/dreaming you can expect 30hp - 35hp @ 3600RPM and weights direct drive north and south of 40 kilo's. Whatever version you buy (3) three of them would cost in the neighborhood of $3000 -$5100 initial outlay for 90hp - 105hp. See FAR's 61.31 (I) EXCEPTIONS (2) (B) ( https://www.law.cornell.edu/cfr/text/14/61.31 ). These could be used for experimentation reasonable safely in multiples (in case one quits) and would provide abundant power for a single place or two place design. Multiples would also provide redundant sources of electrical power for Nav/Coms and other aviation related devices. While further monies would be required to modify the engines it is likely from the sources I have been following that the cost to a experimenter would be less than double the cost of the initial outlay so 90hp - 105hp @ +or- 120 kilo's for less than 10k.

15. Jan 23, 2020

### blane.c

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One of the easiest ways conceptionally of having a three engine plane is to use a canard type (like a any of the Vari-xxxxs for example) modify the design so each canard can carry a engine appropriately outboard of the fuselage and the third engine in the normal place.

16. Jan 23, 2020

### Vigilant1

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That's true. But their stock fans produce quite a bit of both air volume and (importantly) they can produce pressure at the front of the baffling plenum that is greater than what we can get from dynamic air pressure at normal cruise airspeeds (e.g. 100 MPH). That's >not< to say that the engines won't cool adequately in aircraft (they do seem to cool satisfactorily up to about 27 cc/continuous HP, at approx 100 MPH), but careful attention to baffle design is important.

17. Jan 24, 2020

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