# Briggs vanguard conversions

Discussion in 'Firewall Forward / Props / Fuel system' started by Hephaestus, May 12, 2019.

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1. Aug 28, 2019

### pictsidhe

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On the inteks, the journals are al the same size. The flywheel side are all the same. The PTO has multiple versions. The 1inch PTO is a really bad idea to use. The 1 1/8 looks rather borderline for DD or PTO mounted flywheel. That depends on what grade iron/steel the crank is made from... There are significantly stronger tapered shaft versions, which I'm having trouble finding drawings for. The drawbolt is a bit skimpy on those, but I think I can make it work.

Briggs really likes making a few core versions with as many common parts as possible, and changing just a few external parts. I compared some old 14 and 15hp OHV engines once. The only difference in the parts list for both engines was the shroud. They were clearly the same stamping, bar the paint and sticker...

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2. Aug 28, 2019

### pictsidhe

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Hephaestus. Any chance of you weighing your long block?

3. Aug 29, 2019

### Hephaestus

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@pictsidhe it was 92lbs with pallet dry.

It's gone down to the land of mudboats, crawdads, airboats... Should have it back around Christmas ready to run with dyno stats.

4. Aug 29, 2019

### Vigilant1

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Thanks for the report. So I understand: you looked at the parts listing for various 810cc engines and compared the part numbers on the various bits as a clue to the commonalities between the designs.
Your info on the heads/camshaft might have an error? The 49V is listed twice.

EFI: All the EFI versions of the 810cc (49ci) engines are Vanguard engines, and these have a unique cylinder head
49E: Vanguard EFI, 28 HP. Representative price: $1600 49M: Same as 49T? 49R: Vanguard, non-EFI, 26HP. Representative retail price:$1150
49S: "Professional Series", 26HP. Representative retail price: $925 49T: "Professional Series", 27HP. Representative retail price:$999
49V: Vanguard, 24 HP, Representative retail price: ??

5. Aug 29, 2019

### pictsidhe

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You didn't weight the long block when you had it apart? Weight is an absolutely vital number for the rest of us. More important than the hp your tuner claims to get out of it! My Intek 656 long block, not including flywheel, stator, coils but with the oil filter was 47lb. Basically all the core parts whose weight will change little. with everything but the muffler and starter it was 77. A 656 is going to be very close in weight to the 810.

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6. Aug 29, 2019

### Hephaestus

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No, I decided in the end to let a pro do the playing... He's confident he can get a continuous reliable 50hp out of it at under 70lbs wet with intercooler and turbo.

Many of the airboat/hovercraft guys swear by him, no bad reviews that I can find other than some timeframe issues... And given I don't even have an airframe for it today - I'm ok with that.

Shipping down to Louisiana did suck though

7. Aug 29, 2019

### Vigilant1

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In the B&S lineup of V-Twins, the 810cc seems to be in the sweet spot in HP/LB (at least in as-shipped weight) and also in price. Maybe horiz shaft engines fetch more money-- 23 HP 627cc horiz shaft engines are hundreds of dollars more expensive than an 810.

8. Aug 29, 2019

### TiPi

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Hi everyone,

I have just joined this forum and found this thread. Quite proud to find that my work has already made it’s way here. I have been in contact with a number of the contributors on this thread on other forums or directly. Lots of good info floating around

The Spacek SE33 is the result of my research into a suitable engine for my SD-1 Minisport. When I ordered my kit back in 2012, I did a lot of research into a suitable engine. The prototype SD-1 was built using the Trabant engine (2 cyl 2-stroke), a local engine from the Czech Republic. One of the first builders used a Hirth F33 (single cyl 2-stroke), he changed it soon afterwards to a B&S 38-series (inspired by the Luciole). Spacek offered this engine as well as the Hirth F23 (50hp). A couple of French blokes built SD-1s with Kohler CH750 engines and Igor added that model to his line-up (SE31). Due to the weight, it wasn’t that popular (CofG). The Verner JCV-360 was the best weight/hp 4-stroke at that time. I didn’t like a number of aspects on this engine (now out of production). Crunching the numbers with the then available performance info from the flying SD-1s, I figured that the ideal engine would have 33-35hp, direct drive (and weigh under 40kg FWF, which includes engine, prop, engine mount, exhaust & cowling).

My research then led me to the B&S 49-series. After studying the available info, I concluded that this engine is the best compromise available. I ordered a 49M977 from the US, also in 2012. I managed the get Igor interested enough so that he ordered an engine as well and started his conversion. It was released in 2016 at the Aero in Germany. He encountered a few issues along the way, especially with the oil supply. He tried a Kohler oil pump, check valves and ended up adding an electric priming pump (pre-lube, only activated prior to starting the engine)

My design for the conversion was to turn it up-side down, for the following reasons:
• Keep the prop axis high with no cylinders sticking out the top
• Have the oil pump lower for easier priming
• The projected engine cross section should fit within the firewall outline (no bumps and sticking out bits)
Spacek SE33 features:
• Lightened OEM flywheel (2.0-2.5kg taken off)
• Alu prop extension bolted to flywheel
• PTO stump cut off
• OEM carburetor repositioned, custom intake pipes
• Oil reservoir in bottom of crank case
• Oil dipstick added near governor shaft bore (governor removed & plugged)
• Electric oil priming pump added (to prime/pre-lube the oil pump after prolonged non-use)
• I believe the oil lines are supplying a small amount of oil to the heads for the valve & rocker lubrication
• Currently experimenting with a “heads-down” version
• Prepared a couple of “XP” versions (Xtra Power), gaining about 2-3hp through light porting and valve seat blending
49-series features:
• Best weight/displacement/hp ratio in the 30+hp range
• Forged crankshaft & conrods
• Large PTO-side bearing area (long bearing)
• Sturdy front cover & main case design
Briggs & Stratton 49-series Engine Models:
• 49M977: Professional series, 1-1/8” crankshaft, cyclonic air filter
• 49M877: Professional series, 1/1/8” crankshaft, cartridge air filter
• 49G575: Professional series, tapered crankshaft, LPG/NG (generator model)
• 49T877: Commercial series, 1-1/8” crankshaft, cyclonic air filter, replaced 49M977
• 49S877: Professional series, 1-1/8” crankshaft, cartridge air filter, replaced 49M877
• 49R977: Vanguard series, 1-1/8” crankshaft, external cyclonic air filter, carburettor
• 49E877: Vanguard series, 1-1/8” crankshaft, external cyclonic air filter, EFI
• 49J677, 49L977, 49V677 are also out there, no spec sheets that I have found and very little information. The 49M, 49T, 49S and 49R are the mainstream engines.
• Most engines are available with either a 1” or 1 1/8” shaft.
Problems to overcome when turning the engine from vertical to horizontal:
Oil supply:
I don’t believe that there is enough space between the crank and oil level for sufficient oil quantity. The oil level needs to be well clear of the lowest point of the crank/big end to avoid hitting the oil (results in oil foaming, additional heat and loss of power). A splash plate might help but the best way is to have an external sump extension (if used upright) or dry sump system (upright or heads-down)

Oil pickup: the original configuration has the oil pump submerged in the oil. The pump design is not suitable for lifting oil (self-priming). 2 ways of fixing this: external priming pump (electric) or dry sump tank with oil level above oil pump inlet.
The oil pump inlet also needs to be modified for an external supply, the original inlet is at the bottom of the sump with a small screen clipped in.

Oil scavenging:
• Using the Rotax 912 concept: use the blowby to move the oil from the sump to the tank. Well proven and simple concept. Draw-back is that there is a slight pressure in the crank case (oil leaks, power loss) and a longer exposure of the oil to the blowby gasses.
• Adding an external pump: too complicated unless a second pump could be piggy-backed to the original pump.
B&S have released a “Vanguard Oil Guard” system, essentially a dry sump system with an external oil tank and filter. Primary purpose is to have enough oil volume to go from 100h oil changes to 500h oil changes. This option is only available on B&S owned equipment brands so far, no engine parts list available yet. What I have found out is that they do use a scavenge pump and the normal pressure pump. This end cover would be ideal for a pumped dry-sump setup. Hopefully B&S will release parts info in the near future.

Some specs that I collected along the way:
• Cooling air required: a rule of thumb is cfm of cooling air required is the same as displacement in cm3. This is derived from engineering data available from Honda and Kohler (much more forthcoming than B&S) and my measurements of the air flow on my engine.
• Oil flow: oil pump displacement is 35ml/rev, equals 12 lt/min at 3,600rpm
• Carburetor: 28mm butterfly, 22mm venturi throat, pretty average to poor quality finish in the air passages
• Valve lift: 6mm EX and IN, 1.3 ratio rocker arms (8mm valve lift), exhaust lobe has excessive ramps (EGR effect) and the cam is rather large on lobe separation (119°)
• Starter motor: standard is the starter motor with the detached solenoid (Bendix is self-engaging). The HD starter motor is required for any increase in compression ratio (solenoid starter). Don’t have weights yet for each.
Valve train:
if you are sticking with direct-drive, the only mods recommended are to install steel pushrods to the intake valves and maybe change the valve retainers to billet aluminium (ARC). Valve springs are good for 4,500rpm

This engine is capable to delivering 35hp at 3,600rpm with some work in the carburetor and intake area. I will post pictures and details when I have done my mods, incl flow bench and power numbers. If the prop is pitched for 3,500-3,600rpm on take-off (WOT rpm at climb speed), the cruise rpm will be 3,200 to 3,250 (3,000 for just pottering around) and that engine will be happy all day long.

For a Part 103 (or any other slow and draggy) aircraft, a direct-drive engine is not really suitable. The climb/cruise speed needs to be used as one of the key design criteria for the prop (dia, pitch and prop rpm), then work out from that if a direct-drive engine is suitable or a re-drive is required the get the most suitable prop rpm for the application. The SD-1 is fast enough to use direct-drive at 3,200rpm with a good enough prop efficiency

Prop on PTO or flywheel end: not that relevant from the engine perspective. The PTO end has a much longer bearing and a very sturdy end cover. If the engine is mounted on the provisioned holes in that cover (incl mounting a re-drive), should be no problem as all the forces will transition from the prop-shaft-bearing-cover-mount (or re-drive). The forces applied to the join between cover and case are what the engine has been designed for. Using a different mount could affect the seal between the cover and case.
BUT: all the research and evidence that I have found indicates that a rotating mass at both ends of the crankshaft (prop on one end, flywheel on the other end) is a WHEN, not IF the crank will fail. In order to use the PTO end, the flywheel needs to be removed or lightened sufficiently so that the rotational inertia is no longer an issue. Basically replace it with an aluminium disc to carry the ring gear, ignition magnet and possibly the alternator magnets (alternator is the easiest item to relocate to the PTO end)

OK, this was a rather long introduction of myself.
Here is the link to my new engine website, still work in progress: tipis-ul-engines.mystrikingly.com

I learnt a lot from the VW, 1/2VW, Jabiru and other engine conversion sites and forums and intend on using all that info to build a reliable engine with as simple as possible mods.

Cheers from Down-Under, TiPi

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9. Aug 29, 2019

### TiPi

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The only difference between a 1" and a 1.125" crankshaft is the PTO end. Main bearings are the same. I also believe that all flywheel tapers are the same. There are 4 different flywheels available but that has more to do with the alternator and ignition coils (EFI).

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10. Aug 29, 2019

### TiPi

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I think B&S is streamlining some of the parts:

My understanding of the difference in head P/N is the EX valve (better quality for EFI and Vanguard)

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11. Aug 29, 2019

### Vigilant1

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TiPi,
Wow--thanks very much for the great information, you're clearly in the lead on this. Test clubs, CHT monitoring, a purpose-built flow bench--you are obviously approaching this project in a disciplined way. Welcome, and thanks for the contribution.

When I first stumbled on your site, I thought the engine and basic instructions for modifying it had come from MiniSport and that you were making some modifications (dry sump, etc). Now I understand this has been very much an independent effort on your part.

Per your research so far, will the ability of the heads to shed heat be the limiting factor in continuous HP? And, with proper baffling and in aircraft use (prop blast and cruise-speed dynamic pressure available, no dedicated blower), what are you expecting the max continuous power to be (with reasonable CHTs--maybe 350 F (175 C) to 375F (190 C)?

Are you happy with the decision to go with the 49M engine rather than the 49R engine?

Your web page indicates you intend to use an aluminum flywheel, and that the prop will serve as the required rotating mass. Have you decided to mount the prop on the PTO end?

Comment: Spacek's overall approach (prop extension bolted to a modified existing flywheel which retains all the stock functionality) is certainly an economical way to go, and does keep all the rotating mass on one end of the crankshaft. I think many people look at the prop extension and that flywheel-side bearing and have some questions, but if it proves out in long periods of actual in-flight use, then there's not much grounds for objection.

Your web page mentions that you eventually intend to market parts or even entire engine packages. That's great news, I would think there's a market for an economical aircraft powerplant in this HP and weight range. Even the most die-hard DIY homebuilder would benefit from the ready availability of the required custom bits, some manuals/instructions, etc.

Mark

Last edited: Aug 29, 2019
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12. Aug 29, 2019

### pictsidhe

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What size are the 810 valves? 656 has 1 1/4 and 1 1/16

13. Aug 29, 2019

### Vigilant1

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The chart TiPi gives in post 730 shows the intake valve as 37mm (1.45") and the exhaust valve as 34mm (1.34").

Last edited: Aug 29, 2019
14. Aug 29, 2019

### TiPi

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I still need to confirm this with actual measurements, these numbers are estimates from photos (valve head to bore dia ratios). I haven'y pulled my heads off yet. Had the intake manifold and carburetor off for some measurements and eye-balling.
An aftermarket supplier is listing them as 1.375" (35mm) and 1.22" (31mm). Strangely, the valves are metric (6mm valve stem) in an otherwise mainly imperial engine.

Last edited: Aug 29, 2019
15. Aug 29, 2019

### Vigilant1

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Did these engines start life as a design by Mitsubishi Heavy Industries under contract to B&S? IIRC, at least some of the Vanguard engines were made in Osaka until fairly recently, when production moved to the US. If so, B&S probably didn't care if the internal bits were measured in mm, inches, or cubits, as long as the external taps and fittings were Imperial for commonality with US lawnmower manufacturers.

16. Aug 30, 2019

### TiPi

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There is a significant familiarity with the Generac GN724 engine (same style block, heads etc), the specs are identical to the B&S 40-series. The 44-series is a larger bore (79.25mm) and the 49 a larger bore again (83.81mm). But the engine looks the same. All major dimensions are the same (crankshaft journal and bearings, wrist pin, camshaft bearing etc).
I believe that the 810 (and the 40-/44-series) are a Generac design, this is also the reason that this engine series is unique in the B&S line-up (vertical only).

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17. Aug 30, 2019

### proppastie

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On your site the calculation of the rotational inertia of the prop is much greater than the flywheel (3x)....does any extra rotational mass (flywheel) a good idea?

How much does your conversion weigh?

The horizontal shaft engines are also aluminum? Do they weigh lots more and have other negative factors?

18. Aug 30, 2019

### TiPi

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Hi Mark, Unfortunatley, I was ahead of my build when I bought my engine. I thought it would go quicker, then work got in the way. When I bought my engine back in 2012, there were only a few models available. The 49M977 was the top of the line model (Professional), then in 2014 they renamed them the "Optimum 810" and only the last couple of years where they aligned with the Vanguard and Commercial branding.

CHT: no info available from B&S. Other manufacturers have the following limits:
Honda (GX/GXV): 270°C under the spark plug
Jabiru: 180°C, no more than 5 minutes 180-200°C
VW: 171°C, no more than 5 minutes 171-215°C, max 232°C
SE-33: max 220°C (from German POH)
I'm looking at Jabiru levels if achievable

The SD-1 requires approx 17hp for 70kts, 22hp for 80tks, 30hp for 94kts. The balance to the max output is acceleration and climb speed.

Spacek did have to experiment a bit with cooling baffles but has no problems now. It just requires getting the air to the right places. The SD-1 is relatively easy to cool due to the decent speeds (climb 65-70kts, cruise 80-90kts). Slower planes will need more help (fan), especially in a pusher (trike).

I have a design for an alu flywheel, currently still with the alternator in the original location. To simplify this new flywheel, I might move the alternator to the PTO and have the magnets integrated in the prop hub. That way the flywheel becomes just a disc to carry the ring gear and the ignition magnet (and counter-weight).

19. Aug 30, 2019

### TiPi

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The idea is to remove as much weight as possible and use only the prop as inertia (wooden prop). If you use an extremely light composite prop without the flywheel, you might need to add some mass to the prop end to allow the engine to idle low enough. Big problem with clean aircraft, idle speed too high and you have to stay up till you run out of fuel (or turn the engine off).

If you have a push mower, take the blades off (incl any disc) and try to start it. Just about impossible as the flywheel is not heavy enough (and too small dia).

B&S doesn't have any horizontal engines between the 38-series and the 54-series.

20. Aug 30, 2019

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