Cyinder Base Nuts for 0300

[auxtank]

I’ll be removing and replacing a couple of cylinders on my 0300A soon. The illustrated parts list shows 3/8” and 7/16” flanged nuts (part numbers 531003 and 531001) used to attach the cylinders to the case. There are no plain washers, lock washers, or pal nuts shown. From prior experience I know that these nuts are sometimes a little banged up because it can be difficult to get the wrenches to fit well. Therefore, I am considering having new nuts on hand to go with the new cylinders. I will be ordering some replacement stainless hardware for the exhaust, spiral exhaust gaskets, and a few other odds and ends from Aircraft Spruce. They do not appear to stock these part numbers or any flanged nuts. Is it acceptable to substitute AN (or MS) washers and nuts in this location? If so, is industry practice to use a plain washer followed by a lock washer and the nut or to use a plain washer followed by a nut with a pal nut on top of that? To tell the truth, I can’t remember if this engine had the flanged nuts in this location on the last cylinder I repaired or not. Thanks in advance for any input.

Gordon Sandy
Juneau, Alaska
N4002V (Ragwing)

[GAHorn]

You should order new flanged nuts from http://www.cessnaparts.com/ or another TCM parts supplier. Ordinary AN hardware will have the incorrect hex size and will be difficult to get cyl-base-wrenches to fit between the barrel and the nut. In other words, no ...do not make AN hardware subtitutions. My 2 cents.
Pal Nuts have been discarded by TCM, and or no longer called for, but lots of folks still like them.

[auxtank]

George,

Thanks for the input. I took a look at the flanged cylinder hold-down nuts yesterday, and they don’t look too bad. Their good condition and the fact that new ones run about $22 for a set of 6 ($44 for the two cylinders) has made me decide that I can most likely take these off without damaging them.

If my memory serves me correctly, some cylinder wrenches are not ground thin enough, so they hit the cylinder and don’t fit down around the hex of the nut as securely as one would like. I’ll see if the owner of the wrenches minds if I grind them a little if I run into this problem. The two new ECI Titan cylinders should be here today or tomorrow and I hope to get into a hangar this week.

If anyone is interested, I decided to order new cylinders to keep the down time to a minimum. The two problem cylinders (1 and 6) tested low at the annual with leakage at the oil filler. We inspected for cracked rings and, not finding either cylinder to be scored, treated them to a little Marvel Mystery Oil bath. This did improve the compression in the lowest cylinder, but 20 hours of flying in the last couple of month (including some time on a search near Sitka for a missing Beaver with 5 onboard) did nothing to further improve their compression. In fact, they were a bit lower when I retested them.

Also, the cylinders, because they are on their second run with a total of 2800 hours, have a good chance of showing cracks or being un-repairable for other reasons. Rather than spend time and money shipping them out and having them inspected––only to find out that they have serious problems, I was advised that new cylinders would be the way to go, and I agreed.

By the way, ECI recommends running-in replacement cylinders with AD oil. “Because the lower end of the engine is already well broken in, AD oils will keep debris from break-in in suspension so that it can be filtered out and not reach the critical bearing surfaces” (from their website). Specifically, they recommend “a multiviscosity ashless dispersant (AD) oil such as Phillips X/C 20w-50.” Thanks again for the input on the flanged nuts. This forum is a great resource.

Gordon Sandy
Ragwing, N4002V
A blue heeler (Willie) and a border collie (LuLu)

[GAHorn]

I have never needed to grind the cyl base wrenches, but I did grind a 5/8" combination wrench to speed up assembly somewhat.
The ECI recommendation regarding AD oils escapes my logic. All the oil runs thru the filter and will capture big pieces anyway whether or not AD oil is used.
Problem with their logic as I see it is: AD oils will keep the dirt in suspension even thru a shut-down and will therefore continue to recycle the stuff through all those parts again and again and ....
I'd darn sure stick some magnets on my spin on filter (if you have one) during any break-in. In fact, I keep magnets on my filter all the time, and when I change oil there sure is a lot of gray ferrous material stuck exactly at the place the magnets were located when I cut the filter open.
(I have an aircraft specific magnetic band on my filter, STC'd/PMA'd by RAM Aircraft of Waco, TX, but there are plenty of other such products available on the market. The best ones use "rare earth" magnets of superior strength, but any ordinary magnet will do a good job. Cheapie 25-cent rectangular and circular ones from Radio Shack held in place with tie-wraps around the filter work pretty well also. Just don't move them or relocate them between oil changes or you'll allow the previously trapped particles to be set free.)