So, from the beggining.
A few years ago, a project was carried out as proof of concept for an opposed piston 4 stroke engine. The researcher took two very basic engines and mounted them opposed to each other and went to a dyno bench to get some results. The idea was to see if the performance would be better than the two engines separate. They used a gear drive which was not the best way since it was a little complex to build and tune. It was noisy, leaked some oil and ultimately was operating the its limit.
Then, I started a new project to follow in the footsteps of that initial project. The idea is to get a baseline from a stock engine. Then, get two engines and mount them opposed to each other, sharing one cylinder. Finally, swap the crankshaft with a geared drive and see what are the performance difference of each configuration. The idea is not to see what is the maximum performance but to see the impact of each modification. As such, the goal is to modify the engines the least so that only the configuration modifications impact its performance.
Since the final configuration is an opposed piston engine, a flathead engine had to be used since the valvetrain can be used with little to no modification. I ended up having to buy vertical engines since no other option was available.
In the meantime, I ended up building a dyno bench based on an electromagnetic brake. I could have built it to test the engines in vertical position but I was asked to instead build it to test engines in horizontal position for our tests. And the engines would have to be modified from vertical to horizontal position.
A considered using a 90º gearbox but in the end we abandoned that solution to reduce complexity, mechanical losses and not easily finding one.
Now, I have the dyno bech built and ready to test the engine. I'm still considering testing the engines in vertical position but my professor keeps telling me that he prefers to modify the engines and use the dyno bench in the horizontal position. And the gearbox is a deadend, by the way.
So, now I'm strongly inclined to modify the engines. Right now, I have several options.
I removed the governor (I will cut the rod inside the crankshaft). The carb we wanted to install a 19mm carb since the intake port is 19mm to be able to tune the carb and more easily install a throttle cable. The choke is built into the carb so that's a plus since we'll only use it in the beggining to start the engine.
The exhaust is to be kept stock. One pointing up and the other down. We'll use a fan to help in cooling and clearing the gases coming off the exhaust that's pointing down.
To lubricate it, one of the engines will have a small aluminium piece to splash the oil when it's running. The other, the rod itself will hit the oil splashing it. My professor says that since it's only for testing purposes, it's not a big issue as the engines will only operate for short periods of time (30 min if it can't run any longer).
So, I wasn't going to mess with the lubricating holes in any way. Just move and install a new carb, keep the exhaust, install a dipper to splash the oil if tested in one orientation and leave it be (for the stock engine).
For the opposed piston, I chose to use a timing belt with a tensioner since it's simpler, requires little to no maintenance and is, in my view, preferable to installing a gear train to connect both crankshafts. By syncronizing the crankshafts, I guarantee that the spark and valve timings, and power output is connected and syncronized.
The adapter connecting both engines is an aluminium piece that was designed to be able to install a M10 spark plug, one close to each exhaust port, which will be connected to the magneto. It was also designed to keep the compression ratio the same as stock (6:1). In fact, the engines will operate both as flatheads and OHV, in a way. And there's communication ports between each cylinder which is not a complete hole to be able to keep the combustion volume.
I've been looking at the engines and am wondering if I should not put some JB Weld on the crankcase breather hole and install a breathing plug to put the oil in the engine. The reason for thinking about deleting the stock breathing crankcase hole is to avoid oil accumulating in the valve springs are and, ultimately, going up the breathing tube.
Once again, the idea is to get a baseline of a stock engine, then modify them in different ways and measure the internal cylinder pressure, obtain torque and power curves and compare them. So I only need the engines to work fine, not achieve the best performance possible.
I'll leave some pictures to help understading my explanation.
So, my main issue is regarding the horizontal modification. How to ensure proper lubrication, solving the issue with the oil level which will be low, specially when the camshaft is over the crankshaft (As I said before, I was thinking about letting the rod and counterweights splash the oil and for the other orientation I was considering installing a dipper). Also which carburetor is suitable to make the engine work fine (if PZ16, PZ19, PZ20, PZ22 or something else). Finally, if the crankcase breather tube will give me any issues.
PS: For the carbs, I'm considering using a cable that is used in scooters for the oil pump and throtle which has one end for the throttle and when you pull it, it pulls two cables at the same time. The main jets are something that I want to take into consideration. Also, my goal is not to increase rpms. In fact, it may be a good thing to not go over the stock rpms of the engine to not stress the parts and demand even more lubrication of the moving parts.
And thanks for all your input! I really appreciate all the help you're giving me and all the experience you're sharing.