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

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Jay Dub

Well-Known Member
Joined
Dec 17, 2019
Messages
105
Location
SE WY
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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