One of the last ends to tie up was the protection of the electrical connections inside the Futaba connectors used on the Hall sensor cables going to the ignition modules. This involved making a pair of protective covers by shrinking a length of heat shrink tubing over the connector while leaving a bit of overhang on its open end. A mating male connector, used during the shrinking process, prevented the open end from closing up. The cover slides over and protects the seams between the mated connectors on the ignition modules. Silicone was used to seal the cable to the rear of the tubing.
The step that I've been dreading since the beginning of this project was filling the engine with coolant. The are 76 coolant seals in the engine, and 52 of them are inaccessibly buried in the head assemblies. Although I vacuum tested those assemblies just after the heads were married to the cylinder blocks, my gut never made its peace with this particular feature of the engine's design.
I slowly filled the whole system with about 1-1/2 liters of automotive anti-freeze while checking for leaks, and then I left the engine sitting for several hours. Placing the coolant reservoir at the rear of the engine so it was level with highest point in the coolant loop was a great help, but another half inch or so of height would have been even better. If I had it to do over again, I would add a second filler cap to the top of the header tank at the front of the engine.
Sure enough, a bit of seepage showed up near the front of the starboard head assembly and also near the rear of the port assembly. With the engine filled with coolant but still no prop, I attempted to start it with the carb settings untouched (or so I thought) from my previous accidental start. I got a few pops and then nothing. After several seconds of cranking, raw fuel began pouring out of the carb's intake. My first thought was that I had an issue with the fuel loop. If the pump pressure is too high, excess fuel can be forced out of the bowl vent and create a similar symptom. However, after additional testing, I realized the flooding occurred only while the engine was being cranked.
I was about ready to remove the carburetor (Perry 9400) when I noticed the starboard coolant return hose rubbing against the high speed needle. I could see the hose changing the needle setting as the throttle was moved back and forth. The o-ring friction that's supposed to stabilize the needle setting against vibration wasn't adequate against the moving silicone hose. A simple tie-wrap solved the problem. The remarkable thing about all this was that the throttle had been moved many times since that hose was installed, and yet somehow the needle ended up at just the right setting to allow the engine to start up so easily the very first time.
At this point the needle was sitting at 2-1/2 turns open from its fully closed position which happens to be close to the recommendation in the application note that came with the carb. I went back over my notes for my last radial build that used a very similar Perry carb. That engine had run best with a needle setting 3/4 turn from fully closed.
I reset the needle to 3/4 turn and let the engine sit for a few hours to dry out before attempting a restart. This time the engine started up and ran although a bit rough. I could tell from the exhausts that the cylinders in the starboard bank were firing only intermittently. This time my wife was videoing the run on her iPad.
[ame]https://www.youtube.com/watch?v=2lw-6he7qFY[/ame]
While running there's no oil or smoke coming out of the exhausts - a very good sign, but the coolant leaks opened up some as the head temperatures rose. After shutdown, about a teaspoon of coolant dripped from the engine.
After allowing the engine to cool I made another run. This time I could feel the throttle response beginning to show up, and the engine easily rev'd up even though the starboard cylinder bank was still only intermittently firing. Before quitting for the evening I was able to eliminate the Hall sensor and ignition module as the source of the problem. The problem seems to be in the starboard distributor, and I may have a small phasing issue with the rotor.
I was pleasantly surprised to see the engine which has so much internal gear friction run as well as it did without the benefit of prop momentum. The electric starter also seems to be holding up.
My next step is to figure out the distributor problem and accumulate additional running time before adding the prop. I'm hesitant about adding the prop because I'm not comfortable with running the engine inside my shop with it installed. The engine is very heavy and is going to require a back-breaking effort to navigate it through my crowded shop and get it outside. I want to minimize the number of times I'll need to do it. I then plan to replace my wife's video with one in which the engine is running on all cylinders and with its prop.
The coolant leaks, though have really let the air out of my sails. Most of the engine will have to be torn down to properly address them. Frankly, I think chances are high that if I decide to do it, I will just move the leaks around instead of eliminating them. I'm also very concerned about separating the heads from the cylinder blocks without damaging either or both. I'll need to think more about this before deciding if it's the way I want to spend my winter.
In any event, I've taken a few photos of the final assembly as I don't expect the project's external appearance to change. But who knows? I made need them this winter. - Terry
