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

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Jay Dub

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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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TLAR

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Thanks for starting this thread Jay, I don’t have any facts to share, just a keen interest in what you are doing.
May I ask your opinion on a related matter. What would be the perfect high wing airframe for this engine?
Personally I would like to see Bob Barrows design an aircraft for this engine.
Pops knows him, maybe we can get Pops to ask him.
Maybe I will write him a letter and ask if he would.
Maybe MAP would design one Pro Bono for the Experimental folks.

If we all chipped in the Engineer could make some cash and we get a fully developed ultralight
 
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patrickrio

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I'd be in for $100 just to see what solution came out of MAP's Brain for this. Watching her videos, She even simplificates and adds lightness to her words as if they were also engineered. pretty impressive.
 

GeeZee

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This is great stuff. Trying to pause the Dino vid at 3400 rpm (ish) it’s looking like good power output (and closer to torque peak). so I’m thinking direct drive. Yea I know I’d be leaving HP on the table but hopefully reliability would go way up and it almost sounds like it’s idling at that RPM ;) So if we could talk these guys into an aviation version how about a new billet crank with a significantly larger dia output shaft (dia to be determined by how much the bearing could be increased on the case). the crank could be a bit longer as well to get the prop hub away from the engine a bit. The case is apart for machining the big bore anyway so it shouldn’t add much to the cost. cost of redrive vs billet crank might be a wash.
 

karmarepair

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A new crank you're looking at $1000 in quantity, if you could get someone to make it.

But I'm with you on the POSSIBLE advantages of direct drive. A bigger cam, some intake changes, compression increase (thin copper head gasket vice stock thicker composite gasket), ignition advance, maybe some intake changes. Less weight and money and total thrust than a redrive, but COULD be better overall VALUE.
 

Victor Bravo

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Sorry for the drift. I went through this same path for a Kolb Firestar a few years back. Exact same path.

Wound up using the HKS-700, and because I had the wrong gearbox (3.5 to 1) the airplane never performed well enough for flying it at a municipal airport in mixed traffic.

FWIW, the SUM TOTAL of what I learned is that the right option for the Firestar really is the 50 HP Rotax or 55HP Hirth 2-strokes.

Other stuff "will work" but everything else comes with a bunch of baggage that combines with the limitations of the Kolb airframe, and complicates the living s**t out of the entire process.
 

GeeZee

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Dan W of SPA Panther sells a billet crank for the vair. We could talk to his vendor. If someone drew it up in CAD then it could shipped out to any number of the CNC machining centers for a quote. Not at all sure about what it would cost or if we would need the extra strength but there’s a small commercial forge a few miles from me.
 

patrickrio

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I'd be in for $100 just to see what solution came out of MAP's Brain for this. Watching her videos, She even simplificates and adds lightness to her words as if they were also flight engineered. Laconic and impressive.
 

Jay Dub

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TLAR, I'm a big Bob Barrows fan. I almost built the original Bearhawk several times and still have plans 767. That 4 place is quite the performer. As a former bush pilot I really liked what the "Helio Courier expert" with JAARS had to say after flying one with the Lyc 540 in it. His words were something like "I've never flown anything that can perform even close to a Helio but this thing is pretty close." I did build some aluminum fuel tanks for my buddy's Bearhawk and did some welding on his fuselage for him. I wonder if the Vanguard 993 would work in the Bearhawk LSA? I kind of doubt it but I haven't kept up with the Patrol or LSA much. Do you know what power the LSA version requires?

Forget billet, if I'm buying a crank I'd want a forged crank. Many people don't know the difference between forged, billet, and cast but that difference is huge. For those that don't know cast is melted metal poured into a mold of some sort (sand, steel, or investment wax). Billet is taking chunk of metal and cutting it all up by machine to make the part. While billet is typically stronger than cast it is not nearly as strong as forged because the machining cuts through the grain structure. Forged is heated metal (think 2100F, very orange colored hot steel) to make it "plastic" (the term in the industry as I worked in the forging industry) or a bit soft. It's not really soft but it's not hard metal either. Then the plastic or soft metal is slammed between a die or a series of dies to move the metal out then finished in a "finish die" to the desired shape. This makes the grain structure follow the die lines and is much stronger as it has been compressed into the die, squeezing the grains tighter. I wonder if the Vanguard 40hp EFI engine has a forged crank as some of the Vanguards come with forged cranks like the 810cc vertical shaft? I know Briggs did make a lot of changes when they made the 993 40hp EFI. It is their "hot rodded version."

VB, while I have known the Klob (as my friend Chuck Slusarczyk, the designer of the CGS Hawk, used to call them), I have never known them well and their quarks. I wanted to get back into flying again so I wanted to go this route for the folding wing as I don't live near any airports. I'll probably use a remote paved road since I live in a remote area. I'll trailer it, unfold it at a dirt road intersection, fly, then fold it and trailer it back home and put it in my garage. I learned they don't put any washout in the wings and there is little dihedral (my Hawk would mush rather than stall with the stick fully aft and the engine at idle but I hear the Klobs have little warning then stall without a buffet). I picked up a partial 1994 Firestar 2 kit a year ago really cheap and will be picking up an entire 2014 Firestar kit in a few weeks. The partial kit came with a Rotax 447 with 12 hrs on it and a 2 blade Ivoprop, ground adjustable. I'm replacing the seals in the 447 and so it will be like new but it's a 1994 model. I always thought my single seat Hawk Arrow (3rd one made IIRC) with the 447 really performed well. I'm concerned that the Firestar isn't going to perform as well for a few reasons. The biggest reason is I don't fly at 750' msl as I now live at 4600' msl. I'm guessing the 40hp is going to be closer to 34 hp most days but closer to 30hp on the really hot summer days. While I flew a buddy's Hawk with the 503 DCDI, I don't like the excessive fuel burn. If a 993 Vanguard with a redrive would put out ~50hp for takeoff (which it appears it can easily do), I'd like to put it on the Firestar. Since you went down a similar road, I'd love to pick your brain about that idea since you went down a similar road in the past. I know the big issue for you was the gear reduction had a bad ratio for your application but I'm sure you learned other things too. I do not plan to use the piano hinge and will use eye bolts like the Hawk. It's quite possible I'm overlooking some major issues with the Klob. If you'd be willing, I can PM you my phone number to discuss when you have some spare time and it matches my spare time.

Thanks,
Jay
 

TLAR

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Jay
Just want to make sure you know about the Bob Barrows Ultralight!!!!!!!!!!!!
It is coming, just have to abide by Bobs timetable
Truly good times are in the pipeline!!!!!!!!
YouTube
Bob Barrows Electric Ultralight Flying Machine
 

Geo

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Hi Ya all, I'm new to this web site. I'd like to add to some of the notes that caught my attention. The engine outs with the 447. We had a guy retired and bored thought it would look better to mount the fuel pump stationary on his CGS hawk he was 5 rows of potatoes short of making the runway. The fuel pump is meant to hang on the fuel lines as not to tranmitt the vibration from the engine. this will dampen the action of the diaphram of the fuel pump it won't keep the carbs full and you go lean burn the piston. Also oil to fuel mix can be a problem check the material the sleeve is made of!! Kawi has a nickasell sleeve it does not retain oil like the graphite flakes in cast iron like the rotax has. 32oz to 5 gal gas is the recommended for Kawi. I know of 2 seizures due to wrong mixtures. I have 500 hours on the little eagle with a 440 Kawasaki engine belt drive reduction. Some years ago toward fall here in Wisconsin as the temp dropped she didn't purr right?? After much screwing around while talking to a friend I slid the needle thru my fingers I could feel the wear on the needle jet, not to mention how much wear would be on the jet seat. a new needle and seat and a trip to nappa i got a small o-ring to slip over the needle clip to hold everything stationary. as for the belt drive i increased the distance between the pulleys so ya have more contact arc on the engine pulley and put the bolts from bottom up in the pillow blocks to prevent the thrust load across the threads. Thats enough..........Geo.
 

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Jay Dub

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Jay
Just want to make sure you know about the Bob Barrows Ultralight!!!!!!!!!!!!
It is coming, just have to abide by Bobs timetable
I watched the video. Bob's such a nice guy, it was good to see him on video.

I'm already starting a Kolb Firestar but I think you are right, Bob's little plane might be a good platform for one of the Vanguards.

Jay
 

Jay Dub

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Facebook has a VTwin aircraft conversion group with lots of information
That's fine. Some of us aren't participants of Facebook for many various reasons. Me included and I have no plans to join fakebook. I know I'm not alone.

I wish people that started groups on FB would realize there are many of us that won't be a part because of how those platforms are run and or monetized.
 

Pilot-34

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That's fine. Some of us aren't participants of Facebook for many various reasons. Me included and I have no plans to join fakebook. I know I'm not alone.

I wish people that started groups on FB would realize there are many of us that won't be a part because of how those platforms are run and or monetized.
I feel the same way but yeah I don’t wanna donate enough money for them to start their own website.
 

karmarepair

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Facebook has a VTwin aircraft conversion group with lots of information
I was a member of that group, then I wasn't, and now I can't even find it in Facebook. The guy who set it up did not seem to know what he was doing, but it did have some good information.

There is an Io.group about the same subject, for the volume of posts is quite low.
 
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