# 810 Briggs Rabbit Hole - New Head Branch

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#### Hot Wings

##### Grumpy Cynic
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but the price for that is still unknown.
IF - we don't run into any odd problems (like hydraulic lock after shutdown or having to add an oil control rings) then the extra $'s to convert to inverted is going to be minimal compared to an upright version. By minimal I'm thinking <$500 for a purchased kit for DIY conversion of a stock engine to inverted. The rest of the conversion should be comparable in cost to an upright.
Of course the engine mount, ducting, and addition of a dry sump tank will be different.

Purpose built heads? ??.......if they ever exist. Right now just a classic example of Vaporware.

Motivational? More so for me than I had expected. Not a good thing for my overall productivity.

#### Vigilant1

##### Well-Known Member
IF - we don't run into any odd problems (like hydraulic lock after shutdown or having to add an oil control rings) then the extra $'s to convert to inverted is going to be minimal compared to an upright version. By minimal I'm thinking <$500 for a purchased kit for DIY conversion of a stock engine to inverted. The rest of the conversion should be comparable in cost to an upright.
Yeah, I was also including the nonmonetary costs, just unknown challenges of flipping it over. Just because none of my own projects ever go as smoothly as I imagine they will. Like, given all the oil flailimg around in that case and all the rotation going the same way, won't a lot more oil end up in one piston skirt rather than the other? What does that mean for balance/vibration? See? -Probably nothing to worry about at all, but that's because I haven't imagined the truly important boogeymen laying in wait.
I think TiPi said that the MiniSport folks were working on a heads-down version, maybe they'll discover any landmines first.

#### Hot Wings

##### Grumpy Cynic
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More bits to see what fits where. Equalizing intake port length with a single carb is going to be a challenge.

Cooling ducts may be completely off for a stock head.

#### TiPi

##### Well-Known Member
Log Member
now you will make the Lancair drivers jealous, having the same frontal look but at a fraction of the cost
Tell me about trying to get the intakes the same length. I have pretty much given up on that and will live with the 21mm difference. I'm still considering the removal of the choke plate which would open up the possibility of adding different length intake trumpets to the carb intake and balance the intake tube length this way. At WOT, no problem. At idle, the different volume (throttle plate to valve) might have some small effect.

#### Vigilant1

##### Well-Known Member
Warning--Likely dumb question: Would it practical or useful to can't/skew the carb a bit, approx 45 degrees, so that the back of the carb body is perpendicular to a line between the two intake flanges and the runners would be the same length? It might look unusual, but . . .
Again, I'm pretty sure this would have been considered, but I specialize in making the obvious points.
Edited to add: I see from the next post by Hot Wings that this idea was already considered.

#### Hot Wings

##### Grumpy Cynic
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Tell me about trying to get the intakes the same length.
Haven't given it much thought other than to notice that they are different length due to the cylinder stagger. My first thought was to put the carb at 90 degrees to the ports centerline - canting the carb with respect to the longitudinal axis/twist around the yaw axis - thus allowing the tubes to be the same length. This means one tube then has slightly more turn than the other. Still not ideal and makes fabricating the bits harder.

My long range goal is to use EFI so staggered throttle plates seem like the ideal solution?

After several iterations it looks like the stock exhaust flange location and an intake flange rotated 45 degrees is the best compromise for for all 4 orientations of the engine. All the machining, except the intake flange face, is then simple 90/180 degree setups.

#### WonderousMountain

##### Well-Known Member
The 90° carb seems like a good idea,
Canting it might not be as good of a
look. An offset might acheive the same
without making the builders answer for
hot Wings particular genius without par.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Probably overthinking the different intake runner length between the carb and the head?
Just make the upstream runner a bit longer on the proper side. Aircraft run at basically one RPM and near full throttle so there won't be much difference if the throttle plate is of a centimeter or so from the other.

#### pictsidhe

##### Well-Known Member
A bit of kinking of the short runner should get you close. If you don't, it's less than an inch, may not make a measureable difference.

#### pictsidhe

##### Well-Known Member
An outward-ish exhaust port would be better for flywheel forward mounting and still ok for PTO forward?

#### Hot Wings

##### Grumpy Cynic
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An outward-ish exhaust port would be better for flywheel forward mounting and still ok for PTO forward?
If you mean like this?:

A couple of my untouchable parameters are to keep the major bits in the stick location - unless there is very good reason*. The red lines make machining, and torquing of that one head bolt problematic. I tried ports angled at 45 degrees to the stock (possible and still get to the bolts). It does move them further from the prop arc, but it created other packaging problems with a couple of the 4 possible orientations. The only work around - that I could see - was 2 sets of heads. one with the port twisted 45 deg outboard and the other twisted 45 deg inboard.

As is all of the existing aviation exhaust systems for the 810 will still bolt on.

Initial machining of the twisted intake ports is harder but making the manifold would be easier with parallel surfaces. If this was the only reason I'd probably even leave the intake port in the stock location. Moving it longitudinally also frees up space for a pushrod tube allowing the removal of the wall under the rocker stands - and - the second plug. This frees up lots of room for better air flow and more cooling fins. The pushrod tubes and matching holes are easy to machine and sealed with o-rings similar to the TP IV VW.

For the project that started me on this adventure (Quickie - inverted/flywheel forward) the twisted exhaust port to the inside would be the best, but once all the casting patterns and tooling jigs are built for one ...............it is a "small" step to making several. I can work with stock ehaust port locations for the Quickie.

Pic above also shows equal length intake port runners. Just the throttle plate is offset.

*Admittedly at this point it may well be my subjective assessment.

#### pictsidhe

##### Well-Known Member
Yes, like that. I said 'ish' as I had a feeling there was a head bolt issue. Maybe I should go look at mine...

#### pictsidhe

##### Well-Known Member
Have you picked valves yet?

#### Hot Wings

##### Grumpy Cynic
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Maybe I should go look at mine...
No need to look. By extending the port out a centimeter from as drawn it clears the bolt hole - but increases the length of the aluminum part of the port if not using a steel insert.

edit:* or rotating the flange about 90 deg. Corrected pic

Valves? They could be any size desired but I'm sticking with the stock parts. Easy to source spares and come with the basic engine. Builders can them just swap into the new head ans dell the unused OEM casting on eBay. Tooling for other size seats would not be that much extra work.

Haven't really thought about seats yet. Lots of new technology out there but don't know how much of it is available in the size range we need.

* Wife working from home. "Why is my microphone not working? I can't log on to Discord. What is that beeping? Why can I only see 2 of the 5 people in this meeting?" No appropriate emoticon available.

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#### Hot Wings

##### Grumpy Cynic
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Rained out of painting and other outside work this afternoon so............
Stuffing this all under a cowl for the Quickie is going to take some interesting shapes. The forward intake port is the problem child.

#### TiPi

##### Well-Known Member
Log Member
put the prop on the PTO, problem solved

#### Hot Wings

##### Grumpy Cynic
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Log Member
put the prop on the PTO, problem solved
Yup. But it introduces a couple of other 'problems'.
If I could figure out a simple, light and easy to build mounting system that jwould leave the OEM mounting pads free I'd have to reconsider my current choice of prop on flywheel side.

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#### TiPi

##### Well-Known Member
Log Member
My plan is a "semi-bed" mount, picking up the bottom mounting points at the PTO end. Then make a couple of brackets to mount on the starter motor pad and the 2x 1/4" threaded holes on the opposite side (used to mount the ducting). These mounts would be connected to the bed mount with rubber isolators in compression (or similar to the Rotax 912 style).

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Enough of the head dreaming for a while. Getting close enough to having space to work again I need to get back to the basics. First thing to mod for inverted is the oil system so that is what comes next.

the 2x 1/4" threaded holes on the opposite side (used to mount the ducting).
Those sure look tempting to use but they seem pretty small. I've sketched out a kind of 2 piece mount that uses the top OEM mount holes with the tubes coming up the valley. Not simple, but possible. Dynafocal mounts are on my list as well.

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