Briggs & Stratton 627cc engine info/no theory, just the facts!

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Jay Dub

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We call this "Experimental Aviation" for a reason. If you are a theory person or a "thrower of wet blankets armchair engineer", please don't reply to this thread. We only want to know what does or does not work by experience in the air not by some idea in between your ears. Just the facts ma'am, just the facts on the Briggs & Stratton Vanguard 627cc engines that have flown or are flying.

A lot of these engine threads become theory threads with "armchair engineers" saying why it can't be done, or people throwing "wet blankets" on ideas like "TV will ruin everything", or "it's not as good as certificated", or "stick with Rotax or Hirth", and showing spreadsheets to try to prove their theory. Naysayers keep quiet, what we do know is that others are experimenting and flying them successfully, albeit with some issues, and learning how to make it better. I want to know in the real world what has and hasn't worked so far so this can be somewhat replicated by others.

Who flew, what was their setup, and what worked and what didn't work:

The first person I heard of was Kevin Armstrong "Factory Fit" from the UK who flew one for 160 hours on a trike. He even flew it across the English Channel so I'd guess he trusted it a bit. He did several things with his engine and freely shares what he did. In a nutshell, and this may need to be updated as I'm going off of memory, he put in some racing parts such as SS exhaust valves, HD valve springs, high ratio rockers, high comp pistons, forged connecting rods, homemade tuned exhaust, hot cam, light flywheel, Ace Aviation redrive 1.8:1 ratio, carb off of 993cc 61 series B&S with the jetting option above 5000’ (pn845273 but you have to open the intake for the butterfly to clear), and the governor removed. He estimated it made 35-39hp at or above 4500 RPM, and used between 5-6.2 litres/hr (1.3 to 1.6 gallons/hr) of auto fuel. It came in at 40kg (88lbs with the exhaust) or 32-35kg (70-77lbs) w/out exhaust. Even running it fast and hard he kept the fan cooling and the CHTs never got too hot so the heat rejection worked well. There are several videos of him flying this engine. For some reason this setup was prone to carb icing using the Briggs big carb and he had to land several times because of it. Eventually the cam broke (he had been running the engine at 4k rpms continuous for about 2 hours that day) and that's when he went to work on the Chinese ATV engine (Bombardier clone). He thought the cam breakage was due in part to the heavy springs and the high ratio rockers. Many thanks to Kevin for his work on this engine as I think he might be the forerunner in developing this. I appreciate that he shares not only the good but also the bad. I gleaned that one might not need the "hot rod" parts as it will help longevity to not use them unless you are trying to more than double their factory rated power.

Kleber in Brazil has flown the 627 and 993cc Vanguards. The 627 was on a trike. From what I understand he learned a lot from Kevin but also went down his own path and tried to keep things simpler. He also was using the Ace Aviation 1.8:1 redrive on the 627. He kept the engine mostly stock but he did pull the stock 2bbl carb off and used 2 intake runners and used 2 CV Carbs off of Honda Twister 250cc engines and he said any 32mm bore motorcycle carb should work. He has not experienced the carb icing problem that Kevin did. Kleber took unnecessary things off (I don't know what) and said the weight was 38kg (84lbs) in the single carb version, and 40kg (88lbs) in the dual carb version. He said the static thrust was 115-120kg (253-264 lbs) @4150 rpm. He used props 58/34 up to 64/32 and they worked well. Like Kevin, I think there is more to this story and I would love to hear more. I am guessing, but do not know for certain, that he must have used a "high rev kit" because the valves float easily at higher RPMS and maybe a timing key.

The latest person I found who has run the 627s, and I would love to know a lot more, is from Roman Weller in Germany. Roman designed and built the Weller Rebell ultralight. It comes in under EU 120kg (264lb) weight limit. Check out YouTube and search "Weller Rebell" and you will hear some Briggs 627's and they appear to fly well. He started with the 627, then tried a Verner 3V radial but there was too much vibration so we went back to the 627. On YouTube you can find videos of both engines. I don't know if he made kits of this airplane, or sold plans or not but there are several examples flying on YouTube and on the net. I don't speak German so I used Google translate and this is what I learned about Roman's engine. It appears he runs his mostly stock from the specs in his flight manual paperwork. At 4400 RPM he estimates 21.5kw (29.2hp). He is using a redrive, perhaps his own design, running Poly-V-belt at a ratio of 2.22:1. This seems to run a really low prop speed as at 4400 engine RPM the prop is only turning 1982 RPM. Again, I'd love to see his redrive and learn what he has done to his engines as they appear to work and work well. They sound "lopey" almost like a radial when they taxi but sound like a small block Chevy on take off.

Seeing these examples, it seems like this might be a good replacement for the 377 and 447 Rotax models that are no longer made although they are a bit heavier but not a lot more. This is called "Experimental Aviation" for a reason, some are not afraid to experiment.

Are there any other successful flying Briggs 627cc engines that you know of or do you have any more information on the above 3 gentlemen that have successfully flown the Vanguard 627? Again, I just want this thread to be about what is working and what isn't working in real life on the 627 Vanguard, not theoretical discourses. I'd rather this be a smaller thread rich with real-world info and not a 70 page thread of theory and why it won't work that someone has to spend 2 days reading through trash to gain any nuggets of wisdom.

Thanks,
Jay
 
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Vigilant1

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He estimated it made 35-39hp at or above 4500 RPM, and used between 5-6.2 litres/hr (1.3 to 1.6 gallons/hr) of auto fuel.
Just to keep with your 'just the facts" request: If one of these engines is burning 1.6 gph, then it is making no more than about 23-24 HP. Figure on a BSFC of about .43-.45 lb/hr/HP for small 4-stroke air cooled pushrod engines.

Are there any other successful flying Briggs 627cc engines that you know of ...
Yes. A modified version of the B&S 38 series engine is fitted to some MC30 Luciolle aircraft. You might want to check with folks flying them to get a direct report.
 
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Vigilant1

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Also, the B&S Series 38 engine is the basis for the SE24 engine fitted to some SD-1 aircraft. They claim 24 HP in a direct-drive setup (prop mounted on the flywheel end of the crankshaft, a modified version of the flywheel with all the ignition, alternator, and starter ring retained). It apparently performs well in service, though 24 HP limits the payload and climb rate of that aircraft quite a bit.
Here's a web site showing their kit:
http://sdplanes.co.uk/sd-1/engines/se24-24hp-4stroke/

The SD-1 flyers might be able to put you in touch with someone flying behind one of these engines.
 

Jay Dub

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Good information and glad to see we're looking at what is working. I contacted a few more people to get more information from people that are flying with the Vanguard 627cc. I edited my original post because Kleber let me know what carbs he used.

I contacted Roman Weller in Germany, the designer of the Weller Rebell, and he gave me some information. First, one of his engine conversions has 1000 hours on it with no degradation in performance noted. He also told me they started buying Bautek engines (unfortunately the company is going out of business in January 2021 for other reasons) and one of the Bautek 627s has over 2300 hours of flying on it. This speaks volumes to the longevity and integrity even when they are "hotrodded" a bit.

What did Roman do on his conversions? This is all through Google Translate so the wording is a bit different and some is not so easily deciphered. The following changes were made to the engine:
Rev limiter removed
Flywheel turned off / milled off and balanced approx. 4.6kg weight
Feather key made for early ignition 1mm (step on feather key). (Google translate probably means advance timing key and just didn't know it haha)
Turn off the cylinder heads by 1.5mm, the bearing blocks of the rocker arm must therefore be underlaid with a 1.5mm insert so that the 1.5mm be balanced by the twisted head.
We made new valve spring plates because of the preload of the springs and installed them.
The reduction here is 2.29: 1 large wheel D 149mm, small 65mm.
I built a wooden propeller D1.75m H 0.9m.
The maximum speed was around 4300 rpm. on the engine.

Other notes from him state:
Most people cruise at 3300-3400 rpm.
We have a consumption of 4.3l / h (1.1gph) up to approx. 7l / h (1.85 gph).

Bautek info from their website via Google Translate:
Briggs&Stratton, 2 cylinder, 4 cycle, 630 ccm engine 38hp @4100 RPM
Poly V-Belt drive with reduction 1:2,25 or 1:2,0

Tuning Specifications:
New engine, complete disassembly, cleaning
Cylinder heads performance enhancing machined
Valve seats and channels optimization, compression test
Valve springs fitted with new alu-plates
Flywheel turned
Flywheel grooves changed for more ignition advance
Push disc static balancing
Suction elbow shortened, fit and weld
Standard-camshaft regrinding
rpm-limiter removed
Auto deco modified
Carburetor worked-over and new jets installed
Motor-complete assembly, control of tolerances
Adjustment of timing and valve play
Adjustment of magnetic ignition for each cylinder
Attachment of muffler, gearbox and air filter

Some more info on several successful 627s flying and what was done.
 

Jay Dub

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Vigilant1

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Good information and glad to see we're looking at what is working. I contacted a few more people to get more information from people that are flying with the Vanguard 627cc. I edited my original post because Kleber let me know what carbs he used.

I contacted Roman Weller in Germany, the designer of the Weller Rebell, and he gave me some information. First, one of his engine conversions has 1000 hours on it with no degradation in performance noted. He also told me they started buying Bautek engines (unfortunately the company is going out of business in January 2021 for other reasons) and one of the Bautek 627s has over 2300 hours of flying on it. This speaks volumes to the longevity and integrity even when they are "hotrodded" a bit.

What did Roman do on his conversions? This is all through Google Translate so the wording is a bit different and some is not so easily deciphered. The following changes were made to the engine:
Rev limiter removed
Flywheel turned off / milled off and balanced approx. 4.6kg weight
Feather key made for early ignition 1mm (step on feather key). (Google translate probably means advance timing key and just didn't know it haha)
Turn off the cylinder heads by 1.5mm, the bearing blocks of the rocker arm must therefore be underlaid with a 1.5mm insert so that the 1.5mm be balanced by the twisted head.
We made new valve spring plates because of the preload of the springs and installed them.
The reduction here is 2.29: 1 large wheel D 149mm, small 65mm.
I built a wooden propeller D1.75m H 0.9m.
The maximum speed was around 4300 rpm. on the engine.

Other notes from him state:
Most people cruise at 3300-3400 rpm.
We have a consumption of 4.3l / h (1.1gph) up to approx. 7l / h (1.85 gph).

Bautek info from their website via Google Translate:
Briggs&Stratton, 2 cylinder, 4 cycle, 630 ccm engine 38hp @4100 RPM
Poly V-Belt drive with reduction 1:2,25 or 1:2,0

Tuning Specifications:
New engine, complete disassembly, cleaning
Cylinder heads performance enhancing machined
Valve seats and channels optimization, compression test
Valve springs fitted with new alu-plates
Flywheel turned
Flywheel grooves changed for more ignition advance
Push disc static balancing
Suction elbow shortened, fit and weld
Standard-camshaft regrinding
rpm-limiter removed
Auto deco modified
Carburetor worked-over and new jets installed
Motor-complete assembly, control of tolerances
Adjustment of timing and valve play
Adjustment of magnetic ignition for each cylinder
Attachment of muffler, gearbox and air filter

Some more info on several successful 627s flying and what was done.
It seems possible there is some misunderstanding or mistranslation between the parties here. Or, maybe not.
- If the highest fuel consumption Roman is seeing is 1.85 gph, that is consistent with the production of about 25 HP. And that output is also about what we might expect from a 627cc engine at about 4000 RPM, maybe running at slightly higher than stock CR.
- 38HP is the output of an engine sold by Bautek, which is reportedly (per Wikipedia, for what it is worth) based on a "1000cc' B&S engine. They fit this to their Skycruiser trike. B&S doesn't make a 1000cc engine, but they don't make a 630 either. At any rate, 38 HP from a 1000cc engine (or, more likely 993cc) is realistic for aviation service. Those 54 series B&S engines are heavy.
- Bautek also reportedly fitted another B&S derived engine to their PowerTrike Light trike. The displacement isn't given by Wikipedia, but the reported output was 30 HP. A 627cc engine run at 4000+ RPM and high CR might do that, for a little while.

HP numbers should always be viewed with suspicion unless the engine has been run with a calibrated club. That will help us stay with 'just the facts. '
 
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TiPi

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What did Roman do on his conversions? This is all through Google Translate so the wording is a bit different and some is not so easily deciphered. The following changes were made to the engine:

Jay, if you can send me the original in German, I can refine the translation (I'm a bi-lingual mechanical engineer with some French as well).

Cheers, TiPi
 

Jay Dub

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- 38HP is the output of an engine sold by Bautek, which is reportedly (per Wikipedia, for what it is worth) based on a "1000cc' B&S engine. They fit this to their Skycruiser trike.
I wasn't quoting the data from Wikipedia but rather directly from Bautek's own website regarding the Skycruiser right here. They state it's a 630cc engine (which might be how Briggs markets the engine in the EU) and the numbers I posted. They are claiming an engine weight of 29.8 kg (66 Lbs) so that can't be the 993cc Vanguard as I don't think you could get a 993 down much below 90lbs. If they are seeing a climb rate of 590 – 790 ft/min the 38hp figure seems reasonable. Could those hp numbers be inflated? Of course, any time you see marketing you can know most all hp numbers are inflated by one method or another and the same is true for fuel burn.

However everything else aside, does Roman and also Bautek have several of the 627 engines successfully flying light aircraft and with a lot of hours? Yes they do and you can see them on Youtube flying just fine. To be frank, I'm surprised they are getting as many hours on them as they are. To me that's impressive. I'm trying to document what those that are successfully flying the 627 are doing to them to get the power needed to fly an ultralight or what used to be called "fat ultralights" or even just small slick planes like the SD-1.
 
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Stuffengineer

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Thanks for starting this thread. I too as many others are interested in the application and success of these engines.
I don’t work for EPA so I don’t give a If these engines use 1 or 3 gph. The last thing that should be used to judge the horsepower output of an engine is its fuel usage. Even the club method although easy to do on an aircraft engine is open to error of the club maker. It would be nice to see these engines run on a dyno. That would give you the best possible results.
Taken care of these engines do run for thousands of hours. I work with a lot of them that are abused in dusty conditions with infrequent oil changes and they still continue to give service.
 

Jay Dub

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Jay, if you can send me the original in German, I can refine the translation (I'm a bi-lingual mechanical engineer with some French as well).
Cheers, TiPi
From a PM from TiPi:
Most of the translation is spot-on, here a couple of clarifications:
feather key is the timing key (Woodruff key), offset by 1mm for more ignition advance
the cylinder heads are shaved by 1.5mm, the rocker posts are shimmed by 1.5mm to compensate for the reduced head height (TP: another option would be to shorten the pushrods by 1.5mm, check out "adjusting the valve train geometry")
The "Ventilfederteller" is the valve retainer. I assume they machine their own to increase the valve spring pressure (there is no mention of different valve springs). It is commonly accepted that the OEM valve retainers are not holding up when increasing the rpm so they get 2 flies with 1 hit. I'm using a set from ECCarburetor for my engine.

On the Bautek:
They are building the engine to closer tolerances, the carburetor is bored out at the jet (TP: I think this is the venturi, not the main jet)
They are also re-grinding the cam lobes to change the valve open/close timing (TP: the OEM cam on my engine has a very slow ramp, info I found suggests that this is done as a built-in exhaust gas recyling for emission control)

I have been in contact with another German engine builder who is using the 627cc engine. They have measured between 18 and 22.4hp out of 10 engines. Their biggest issue is the carburetor, same as what I have discovered.
 

Jay Dub

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For the most part it appears most everyone is doing mostly the same such as:
Remove governor
Shim valve springs (in hi rev kit)
Change valve keepers (in hi rev kit)
run a redrive (1.8:1 down to 2.29:1) because running higher engine RPM (4300-4500)
needs a different carb (993 carb, single or dual motorcycle ie 2 32mm carbs)
regrind cam or get a hotter cam for more power at higher RPM (some use stock cam)
Use a 1mm (some say 8 deg) offset flywheel key to advance the timing.
Some lighten the flywheel and get balanced
Some raise the compression by either milling the heads or changing to high comp pistons. (If doing the pistons you need to get the flywheel balanced so head milling might be simpler)

Just the facts, it seems like those that are successfully flying the 627 Vanguard are all doing very similar things, some do very little, others do this and more.

I've come to the conclusion that my Density Altitude in the Summer will not allow me to use this engine in my Kolb Firestar build. I've been looking at the Big Block Vanguard 993cc engines. They will be about 15 lbs heavier than the Valley Engineering Big Bad Twin but I believe one can make similar power. I'll start a new 993 thread.

Thanks everyone,
Jay
 

Jay Dub

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I just started a new thread for conversations on the 627cc Vanguard so we can throw out ideas there and not clutter this thread with drivel.
 

TLAR

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The reduction drive on the valley engineering big twin is pretty heavy. 3 sprockets. Redrives without tensioner/idler sprocket and related tensioning mechanism will be lighter.
How do I know, because I had one and have it reverse engineered.
 

Jay Dub

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I just started a new thread for conversations on the 627cc Vanguard so we can throw out ideas there and not clutter this thread with drivel.
Please keep this just the facts thread to just the facts on what is working on the 627 Vanguard, not Valley Engineering, etc. I started the 627 conversation thread here for conversations and ideas.

Thanks,
Jay
 

erkki67

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Hello Jay
Roman Weller is using an Engine modified by Bautek. It’s a 627cc B/S.
The engine is available with two different reduction ratios 2:0 and 2:2,25.
~38hp
The noise emitted was measured at a level of 57db.
The tuning is carried out by a Gentleman named Dipl. Ing. Gottfried Michels.
rgds Erkki
 
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