# Briggs vanguard conversions

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#### Armilite

##### Well-Known Member
I've read through 17 pages of messages and have tried to keep all of the info straight but it gets quite confusing with the conversation going in 10 different directions pertaining to half a dozen different engines......
I'm not seeing the point of spending $700-$1,100 on an engine and then throwing everything away except the cases ....and then spending $2,000 replacing all of the parts that were just tossed from a brand new engine. So here's a few questions that will hopefully get answered without too much information drift. So where does it stand at this point....??? 1. Is 35-40 hp possible from a "stock" engine......no turbo,crank replacement,pistons and rods replacement,valves replacement or cam replacement......"stock" off the shelf engine..strip it down,bolt it up and fly ? 2. Reduction or direct drive ? A. Reduction : gearbox or belt ? B. Direct : pusher or tractor.....which end to mount prop on.....will the crank stay in the block without a thrust bearing ? 3. Weight of engine after all unnecessary parts are removed... A. With electrical system...alt,starter and battery ? B. Without electric system...no alt,starter or battery and just hand prop it ? C. Flywheel.....needed or not ? 4. Horizontal or vertical shaft ? Kevin >>>>> 1. No, there isn't a Stock Single or V Twin Engine I would just put on a Plane that makes 35-40hp. 2. Belt Reduction is Best. I haven't seen a Good Gear Drive Conversion yet, but may be possible. 3. Your going to have to figure that out, each Type of Engine will be different. 4. Yes, you want Electrics, with Electric Start, use a Lithium Battery. 5. Horizontal is easiest to convert. There is a 35-40hp@3600rpm EFI V Twin Engine's out there, but you still need to Modify them for Airplane use. READ POST #336 of this Thread. The Big V Blocks you need to lose as much Weight as you can. For Durability for these Singles & V Twins! 1. Valve Train, use Needle Bearing Roller Rockers, HD Valve Springs for Max rpm used, HD Valve Locks & Keepers, use HD Chrome Moly Push Rods, Billet Lifters, Stainless Valves. Even if using Stock 3600rpm, Upgrade the Parts. 2. Billet Rod. 3. Billet Cam 4. Billet Aluminium Flywheel. Stock Flywheel is Good for up to 5000rpm, but you Save a lot of Weight with the Billet Aluminum Flywheel. 5. Use a Good Full Synthetic Oil, like Mobil 1 ($7.88 qt) if Non-Filtered, means you have to change it more often. If Filtered I would use Mobil 1 Gold ($8.96 qt) 15,000 mile Oil, Walmart has it the cheapest in 5qt Containers. Some V Twins have Oil Coolers, I would use a Bigger one than Stock. Most Engines come with a break in Oil that needs to be changed shortly after Break-in Period they Specify. That would be a good time to Open the Engine and do the Mods needed for Airplane use, like Disable Governor, Disable Low Oil Sensor, Install Hi Rev kit, etc. Good Time to deburr and Polish all internal parts. 6. Use the different Engine Coatings to reduce Heat. 7. Take Out Heavy(4-5lbs) Balance Shaft & Balance the Engine Assembly. 8. Since most Airports only carry 100LL anyway, Design & Tune it to run that Fuel. Solves any problems from Detonation or Old Bad Fuel. A Vegas Carts 625 Single,$850 is 626.3cc and rated 23hp@3600rpm. It could make your 35-40hp easy with the mods I listed.

The Small Block V Twins go up to 627cc 23hp@3600rpm!
https://www.vanguardengines.com/na/en_us/engines/horizontal-shaft-engines/small-block-vtwin-horizontal-shaft.html

The Big Block V Twins go up to 993cc.
https://www.vanguardengines.com/na/en_us/engines/horizontal-shaft-engines/big-block-vtwin-horizontal-shaft.html

Big Block Engines:
Vanguard® 25.0 Gross HP* 896cc
Vanguard® 27.0 Gross HP* 896cc
Vanguard® 29.0 Gross HP* 896cc
Vanguard® 31.0 Gross HP* 896cc
Vanguard® 33.0 Gross HP* 896cc
---------------------------------------
EFIVanguard® 35.0 Gross HP* 993cc
Vanguard® 35.0 Gross HP* 993cc
EFIVanguard® 37.0 Gross HP* 993cc
EFIVanguard® 40.0 Gross HP* 993cc
Vanguard® 40.0 Gross HP* EFI - Marine 993cc

Compare these 993 Engines probably just different CAM used.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
So where does it stand at this point....???

1. Is 35-40 hp possible from a "stock" engine......no turbo,crank replacement,pistons and rods replacement,valves replacement or cam replacement......"stock" off the shelf engine..strip it down,bolt it up and fly ?
2. Reduction or direct drive ?
A. Reduction : gearbox or belt ?
B. Direct : pusher or tractor.....which end to mount prop on.....will the crank stay in the block without a thrust bearing ?
3. Weight of engine after all unnecessary parts are removed...
4. Horizontal or vertical shaft ?
At this point it's all just talk. There are a couple of us that really 'need' this engine. I'm one. Here is my plan - to fit the 2 planes where I plan to use it.
1) Possible - from the Big Block 1L engines. For the 810cc that I have.....maybe.
2) This depends on the airplane, not the engine, unless you plan to spin it much faster to make Hp. One of my planes is prop diameter limited, the other has a much higher cruise speed. So both of my planes will use direct drive and maybe spin the engine in the low 4000 rpm range. The fast one will use a CS prop.
2 - A) If I was to use a PSRU it would be belt. Much easier to design and source OTS parts
2 - B) One of my planes is a tractor the other is a pusher. Thrust bearings are not a problem. 30 hp = only about 150 pounds of thrust direct drive.
3) I have a weight budget of 90 pounds, with electric start. I don't expect any problems for the tractor. The pusher with it's 20 inch shaft - maybe.
4) 810cc vertical for me. It's the best compromise between weight, Hp and cost. Conversion to horizontal is trivial - compared to amount of overall modification needed.

Other thoughts related to your original line of questioning:

5) EFI or not. EFI is a really good idea overall. The stock B+S EFI is just fine for ground use. It has 2 features that make me think it may not be the best idea for aircraft. It has a single point failure mode if it looses signal from the Hall crank sensor. This is going to be hard to work around. The other is the way the system shuts the engine off it it senses low oil pressure. The work around for this is not too hard but introduces other failure modes that need to be considered.

6) Which end to put the prop on?
The PTO end has much better bearing surface with regard to gyro loads. It also has a smallish shaft stub with just a key way to prevent twist. There have been reports of breakage here when used with a belt type PSRU.
The flywheel end has a purpose designed tapered shaft to transfer torque, but half of the bearing area/length for gyro loads.

I'm going with the flywheel end - for both the pusher and the tractor version. Why? Torsional resonance. I did some quick napkin grade math and the stub on the flywheel end of the crank with a normal weight prop in place of the flywheel has a resonance just above the max rpm of the engine. Because the PTO end shaft is double the length, and the same diameter, putting a direct drive prop there puts the resonant frequency well into the operational range. It looks like the B+S engineers picked the shaft diameter to be 'just big enough' without wasting material.

If I were to build the best of both worlds I'd probably cut the PTO end for a taper fit and add on a 'third' bearing like the Corvair's 5th bearing. But that costs more money...........

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#### BBerson

##### Light Plane Philosopher
HBA Supporter
If this is for the Quickie single seat, I think it had a 750cc (?) Onan.
So the 810 should do it, especially if high rpm works. Sometimes low rpm and a big prop works better overall.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
If this is for the Quickie single seat, I think it had a 750cc (?) Onan.
So the 810 should do it, especially if high rpm works. Sometimes low rpm and a big prop works better overall.
Yes, one of the planes is my Quickie. It's been setting for FAR too long without a viable engine - NO 2 Strokes!!!
The last version was a 998cc rated at 24 Hp. Most were of the 720cc to 800cc size. All same bore, different stroke.
EPA killed them off. Were made for a few years after in Canada under the Linimar name.

#### pictsidhe

##### Well-Known Member
There are taper shaft 627s and 810s.
For direct drive, forget trying to use the keyway, you need the prop adaptor clamped down to the crank. A keyway will not work. Taper lock fitting will work on a straight shaft, but be heavier ans weaker than using a tapered crank.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Shrink fit hub is used on the smaller VW. Should work for these even smaller v-twin. I like the flywheel tapered end because it is somewhat larger. But yes the bearing surface is shorter, so maybe it will last 2000 hours instead of 4000 hours. Realistically, a 200 hour before overhaul is all I need. The valves generally need re-seating from lack of use.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
There are taper shaft 627s and 810s.
Generally for generator use - which is another indicator that B+S understands the resonance and torque transfer problem. They cost more, but are worth it if you intend to drive from that end.

Point of note: The original Quickie Onan conversion used the straight shaft - with a -4 cross bolt for the prop flange. I'm surprised I never heard of a crank/flange failure.

#### Vigilant1

##### Well-Known Member
5) EFI or not. EFI is a really good idea overall. The stock B+S EFI is just fine for ground use. It has 2 features that make me think it may not be the best idea for aircraft. It has a single point failure mode if it looses signal from the Hall crank sensor. This is going to be hard to work around. The other is the way the system shuts the engine off it it senses low oil pressure. The work around for this is not too hard but introduces other failure modes that need to be considered.
Work around--just a synthetic pulse at the desired RPM to replace the signal from the CAS? If pilot selects, say, 2000 RPM (rotary knob?), the synthetic signal starts at about 10 pulses per second (600 RPM) and over the course of a few seconds ramps up to 33 pulses per second (2000 RPM), so a windmilling/stumbling engine can be "caught" and brought to the right RPM.

Or, the carbs for these engines are cheap enough that a simple one could be placed inline in the induction airstream controlled by the EFI throttle. Turn off power to the EFI, open the mixture valve to the carb, and you're back in business.

The PTO end has much better bearing surface with regard to gyro loads. It also has a smallish shaft stub with just a key way to prevent twist. There have been reports of breakage here when used with a belt type PSRU.
And we do have at least one (short, incomplete) report of a crankshaft break with a Predator (HF) 670cc engine in a direct drive airboat:
Ibuilt a 2 man air boat with one of these motors. I used direct drive with a 2 blade prop and I got 125-130# of static thrust with mine and would push it about 30 MPH. The only problem is their 22 Hp only use a 1" shaft to others use a 1 1/4" shaft for 22 HP and I broke my shaft off. I had used it for one summer with no problems the next spring I fried it up in my yard and the shaft broke off so direct drive I WOULD NOT USE. your set up looks very good to use good job.
No info on which end the prop was mounted or if the stock flywheel (with ignition parts, starter, etc) was retained. My >assumption< would be that the most obvious course was taken: Mount a prop to the PTO shaft and retain the stock flywheel at the other end.

As far as direct drive, thrust bearings, axial loads if prop attached directly to an existing flywheel: We do have some SD-1s flying like this, so that's something.

I'm going with the flywheel end - for both the pusher and the tractor version. Why? Torsional resonance. I did some quick napkin grade math and the stub on the flywheel end of the crank with a normal weight prop in place of the flywheel has a resonance just above the max rpm of the engine. Because the PTO end shaft is double the length, and the same diameter, putting a direct drive prop there puts the resonant frequency well into the operational range. It looks like the B+S engineers picked the shaft diameter to be 'just big enough' without wasting material.
If I were to build the best of both worlds I'd probably cut the PTO end for a taper fit and add on a 'third' bearing like the Corvair's 5th bearing. But that costs more money...
Hey, get on with this project already! I can't wait around complaining forever!

#### BBerson

##### Light Plane Philosopher
HBA Supporter
I scanned through the 196 page manual. It looked like the oil pump was on the bottom (for those models). I suppose because the same basic design is used for both horizontal and vertical.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Hey, get on with this project already! I can't wait around complaining forever!
Just as soon as I get all of my spring cleaning finished, a new fence built, and my shipment from Canada arrives.

Had a chance to think about the work around for the B+S EFI 'deficiencies' while loading tree limbs. It's not as much of a problem as I first thought. It will require an add on Arduino and second Hall sensor. The added failure modes will be pretty benign and only a problem if they showed up after the main EFI Hall sensor quits. My 810 is a carb version. If I can find a take off B+S EFI, maybe on eBay?, I'd probably go that way for testing.

If the B+S EFI could be made aircraft compatible, then IMHO using a carb would be .

#### Vigilant1

##### Well-Known Member
If the B+S EFI could be made aircraft compatible, then IMHO using a carb would be .
Maybe so. It seems to me that discovering all the failure modes (esp the default factory values in case of sensor(s) failure, and assessing the in-the-air impact of flying in those various degraded modes) is a tall order. It might be simpler and better to just have an independent ECU with it's own sensors (or it's own simple default settings and manual controls). Since we can't read or change the B&S code, it will remain a black box that we can only affect by doctoring the inputs and outputs, hoping we truly understand what it might do.

##### Well-Known Member
Log Member
Bayourepairs.com has its Mud Motors listed at 40,44 & 48 hp verified on a dyno...with a 3 year warranty.
And is also claiming up to 75hp on a big block Vanguard with a 3 year warranty.......
Just ran across the site and thought I would mention it....

Kevin

#### pictsidhe

##### Well-Known Member
Claimed hp, not verified. Tuning shop dynos have 'calibration issues'. Wasn't that the site claiming 86ftlb from a 993 with short intake runners?

Delphi ECUs can be and are reprogrammed.

##### Well-Known Member
Log Member
You're right.....it's not a Briggs.
That site is a mess and I was just doing a quick scan...the attached pic shows where I got that from.....it says Vanguard big block....but the pdf doc says GM 3 cylinder.

Kevin

#### poormansairforce

##### Well-Known Member
Notice that on one of the add pics it claims aluminium con rods.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Delphi ECUs can be and are reprogrammed.
If that is true of the B+S version that would considerably simplify the adaptation to aircraft. The older Kohler EFI modules, also Delphi, are available used on eBay for a 'reasonable' amount. Externally they look identical. If they are reprogram-able, and not just the delivery map, I'd presume that the B+S version is too.

#### spaschke

##### Well-Known Member
it shows the 75hp being the GM motor and the vanguard at the lower hp

#### Hephaestus

##### Well-Known Member
We need to talk rv6ejguy into doing a 2cyl version of his system. Probably would work actually just leaving the extra injector plugs off and tuning it that way.

Well my budget is blown for the next few months... Panel upgrade and interior refit ran into some pricey snags, and another month+ delay... Ok and I might have said "while you have that apart" a couple times - and that's never cheap either...

So Briggs build is backburnered for a while...

#### Vigilant1

##### Well-Known Member
There's more info at the link. The price is $350, it weighs 7 3/4 lbs, and a new heavy-duty starter must also be fitted to use this flywheel/starter ring. If the photo is accurate for this exact model (text indicates the photo may not be 100% representative), then it has fan blades as part of the unit (which we might not need). The video at the link indicates there is ignition advance built into the flywheel, and it appears the center hub is steel (heck, it looks like a prop or prop extension could bolt right to it). There appears to be keyway slot in the item in the picture, I don't know if they all have that. At 7.75 lbs, it might save about 10 lbs of weight compared to the stock flywheel and perhaps provide more HP due to the ignition advance. But, another way must apparently be found to make electricity (weight? Cost?), and new starter is required (weight?,$221).
Right now, if turning the engine no faster than 3600 RPM, I'd be inclined to stick with the stock steel flywheel. After adding another alternator and a heavier starter, it's not clear how much weight would actually be saved with the light one anyway. The cost looks like about $571 ($350 flywheel, \$221 starter), plus whatever another alternator solution would cost. The SD-1 folks have apparently stuck with the steel (iron?) flywheel, and they still say they have gotten the engine down to 70 lbs. One reason to like these engines is that they have proven to be reliable just as they come out of the box.