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Briggs & Stratton 993cc "Big Block" engine conversation thread

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Jay Dub

Well-Known Member
Joined
Dec 17, 2019
Messages
105
Location
SE WY
In order to try to keep the "just the facts" thread on the Briggs Vanguard 993cc thread to just the facts, I wanted to make a conversation thread for people to make their comments and throw their ideas out.

After seeing what Midwest Horsepower did on the dyno with the 993 I'm thinking I would start with the carb version of the 35hp model. I'd then change a few things but with OEM parts from the 40hp EFI engine that is hotrodded from the factory. I'd use the 40hp cam, steel pushrods, and heavier OEM pink valve springs, and valve retainers and keepers (although the retainers and keepers might be the same in the 35hp model). I would also add a dual carb system as I think it would probably produce close to 48-50hp at sea level easily using OEM parts with the dual carbs. Since the 40hp EFI 993 is 40hp at 3600 RPM but that it has the parts for max RPM of 4750, I'd like to see what that produces stock at higher RPM and I'd love to see MHP run one stock on the dyno. By using the OEM hotter cam and valve train from the 40, you are keeping with what Briggs R&D developed while keeping the engine in a "long life" configuration. Keeping the CDI and a carburetor system would keep it simple for reliability (except carb ice might be an issue). Kleber in hot and humid Brazil says he has never had a carb ice problem on the 627's and 993's he's built and flown. Kevin Armstrong, "Factory Fit," did have carb ice issues several times with his 627 build.

I'm looking for an affordable 4 stroke for a Kolb Firestar. The 993 is a bit heavy but with the 725lb max gross I think I could work with the 993 for my application. I tried contacting Dick and Sharon Starks to find out how they've liked the Valley Engineering "big bad twin" generac engine on Sharon's Kolb Twinstar. I saw several videos of airplanes they have at their airport flying the BBT and they seem to perform well. I'd like to know how well they've lasted and if they are happy with them.

I'm thinking I will be going down this road later this year. I know some on here are not fans of the Ace Aviation redrive but after corresponding with Kevin Armstrong and Kleber, I am not too concerned about it and will probably go with one. They both have plenty of hours on theirs and I haven't heard of a single problem. Kevin is now running one on his Goakin 80hp v twin without any problems with the redrive. Looking at the airboat redrives I like the Ace one better from a machining fit and finish perspective. This is experimental aviation after all and to each their own. Hey, I flew 450 hours with a 447 and had my share of engine outs. I have nearly 2000 hours behind a Continental TSIO520M that I had to put down due to engine problems too (I had to land but an airstrip was within reach so no crash landings). I could have a redrive failure if I had to I guess.

Jay
 
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