With the messiest part out of the way, it was time to finish up the firewall forward portion of the inspection. Fortunately, Saturday 3/23/24 was a rainy and nasty day, so I didn't have to worry about missing a flying day.
The first thing I did today was to clean and inspect the gascolator. This airplane is equipped with an Andair Gascolator that is, in my opinion, superior to the standard gascolator that just uses a screen at the top of the bowl. This one uses a filter cartridge that is a much finer mesh than the standard gascolator screen.
Where it mounts on the firewall doesn't leave a lot of room for getting the bowl on and off nor for getting to the safety wire holding the bowl nut in place.
In order to get the whole assembly out, all I have to do is disconnect the two fuel lines and the sump drain line. The unit is held to the firewall with two AN4 bolts.
The first condition inspection I did on this airplane, I tried to do this with the gascolator mounted to the firewall and it didn't go well. First, the safety wire was very difficult to get off, not to mention back on, the nut holding the bowl on. Also, since there is very little room to get one's hands in there, it is further complicated. I did manage to get it out and get the filter checked / cleaned. Getting the bowl back on was another story.
The O-ring around the bowl appeared to be in very good shape so I decided to reuse it, even though I had new ones on hand. It was very difficult getting the bowl back on and I must have nicked the O-ring in the process. It turned out, after chasing down other issues (that's a whole other story) I found that the gascolator was leaking and I had to take it apart again to get a new O-ring in it.
Since then, I take it out and do it on the bench. The first time I pulled it out, the bolts were safetied with wire. As mentioned previously, not good access to get in there, so I put it back in using Nord-Lock washers. Makes the thing much easier.
With the unit on the bench, it is time to remove the safety wire and loosen the nut holding the bowl on. Since this has been around for over 20 years, the nut itself is a trifle scuffed up (unfortunately, a few of those scuffs are mine), so it is difficult to loosen the nut without shedding blood. Fortunately, a cheapy rubber strap wrench does the trick. It doesn't need a lot of torque, so a big tool is not needed.
This time, like all of the other times I have done this, there was absolutely nothing on the screen or in the filter bowl. It is, in fact, so clean that I have been sorely tempted to skip this step one year, but since it is the only filter in the fuel system, I just can't bring myself to do so.
With the gascolator reinstalled, I tackled Mag. timing next. The airplane has LASAR mags and they are timed a bit differently than regular mags. The process for checking them is maybe a bit easier than with regular mags, but if they have to be adjusted its the same procedure to adjust them. In this case, once again, they were bang on 25 BTDC.
Since I had to pull the spark plugs out to clean them, I decided to take this time to borescope the cylinders. I started with number one, and all looked good.
After feeling confident looking at number one, I moved to number three since it's right next door. On this one I suddenly got a sinking sensation when I got a look.
The green bit in the photo above got me excited in a negative way. I knew I had heard about green spots on exhaust valves and how that was a bad thing and that by the time you had an obvious green spot it was too late and it needed to be replaced. Ruh-Roh.
As I was still out at the airport and didn't have the time nor the bandwidth (literally, virtually no reception in the hangar at all), I asked Carl if he would do some research for me and he came through very well. He started by sending me the poster that the AOPA puts out about valve health.
As soon as I saw that I noticed that what was depicted as a burned valve didn't look anything like what I was seeing. More importantly, I wasn't seeing what they were showing as very bad.
Next he sent me an article by Mike Busch in the AOPA magazine about valves. Once again, what Mike was showing did not look like what I was seeing. Apparently, what causes that to happen in Lycomings is that the rotator cap on the top of the valve stem ceases to rotate the valve, letting it develop a hot spot, so at the least lapping in place followed by replacing the rotator cap might be needed.
He then gave me another article by Mike Busch on the subject. Figure 2 in that article had a photo of the whole upper dome of the cylinder showing both valves with a caption that read, in part "...the exhaust valve (left)..." Wait, what? Have you figured it out yet? Note in that figure that the exhaust valve is the SMALL one. I thought the exhaust valve was the big one. Nope, I even looked it up in the Lycoming parts catalog, that Carl also sent, and it clearly shows that the intake valve is the big one. So, all this time I thought I was looking at an exhaust valve problem, I was looking at the intake valve. After a little checking, I could find nothing about colors on intake valves. Carl was able to answer that as well. He said "I’m pretty sure that intake valves (and their seats) don’t get hot enough to burn their edges since they are closed when the exhaust gases leave the cylinder. They are also cooled by the fuel/air mixture flowing past them when the intake valve opens." Well, yeah.
So, based on all that, my exhaust valves actually look pretty good. I was even able to get a couple of pictures of the cylinder wall on a couple of cylinders clearly showing the cross hatch still intact.
After lunch I was still a bit anxious about what could be going on with my valves, but I figured I needed to press on because the rest needs to be done anyway. The next odious task was to clean the spark plugs.
As you can see from the above photo, I am using the fine wire plugs. They are about twice the cost of the massive electrode plugs, but they last at least twice as long. They also, at least in my experience, don't seem to foul as easily as the massives do.
There were a fair number of lead balls in a couple of the bottom plugs, but not too much. There were a couple of oily bottom plugs also, but not as bad as I have seen before, on this engine.
The only thing I don't really care for about the fine wire plugs is that they are a little harder to clean. Once again, thanks to Carl for cluing me in to the fact that you can't use an abrasive blaster on the fine wires, so they have to be all cleaned by hand. Turns out, this was not entirely true. There is somewhat mixed instructions about blasting, but Tempest, at least, says not to use glass beads on fine wires. Tempest also has a spark plug manual. Champion also has their own cleaning instructions. Anyway, in about an hour, I had them all cleaned and rotated.
I didn't put them back in just yet thinking I may need cylinder access. I will go ahead and put them back in tomorrow.
I took the "snorkel" off too be able to more easily look behind it and also because it has to come out to get the air filter out. It uses a K&N 33-2060 filter. I had been cleaning the one it came with for years and that is a bit of a pain because it has to be cleaned with their cleaner and rinsed with water and then thoroughly dried before being oiled and that has to have time to wick and get throughout the filter before it can be reinstalled. All that usually takes a couple of days.
This year, I bought a new filter so that I would have a spare and not have to clean during the inspection. Now I can clean it and reoil it when I have time so that it will be ready for next year. With the new filter in place, I put the snorkel back on. It was a little more difficult than the old one since it was new and the rubber abound the edges still a little stiff and not formed to the top of the snorkel.
I next did a good visual inspection of the entire engine compartment looking for anything awry or thinking about becoming awry. I also wiped the engine down the best that I could. Fortunately, during this inspection, I didn't find anything that needed to be addressed.
By this time, it was getting pretty late and I was getting pretty tired. The last thing I did was to check the brake fluid level in the reservoir which is mounted on the front (hot) side of the firewall.
I don't really care for the standard Van's brake reservoir, though it is very nearly bullet proof, and quite inexpensive. I make a dipstick out of a long wood handled cotton swab to determine how much is in the reservoir. It was nearly full, right where I left it. This airplane has the standard plastic brake lines which makes it easy to see if there is fluid (or air) in the lines. It is still a good idea to check the reservoir periodically.
I actually prefer the Sportsman method of using a clear reservoir mounted on the cool side of the firewall. It is very easy to see on preflight and shows the fluid level clearly.
The drawback to this method is that there is an open vent hole at the top of the reservoir and much fluid would escape during inverted flight or negative G's, neither being things the Sportsman was intended to do.
Well, that's enough for today, let's see what tomorrow brings.
Sunday 3/24/24 gave me just what I needed to finish up the firewall forward. I started by putting the spark plugs back in, then I pulled the spinner off to inspect / service the propeller. I went into some detail on the servicing of the prop last year. This year with five pumps of grease on each side, I had grease coming out of the opposite hole, so I called it good and put the spinner back on.
The last thing I did was clean the belly. I never quite got around to that last year, so it really needed it. Fortunately, there was nothing ugly hiding under all that gunk.
Now that the hardest / messiest parts are done, I just have to do the rest.