I am sorely tempted to pull the jugs on my O-320-A3A and replace my 7.0:1 pistons with 8.5:1, along with the heavy wrist pins of course. My research and prior posts here have made me comfortable with the idea of doing so on the narrow deck engine as long as I don’t go any higher compression that 8.5. I do have some considerations though before I do any such work. The elephant in the room is the engine itself. It is a 1978 overhaul with approximately 1900 hours on the bottom end now. I’m a cheap ******* so I hadn’t planned to overhaul it as long as it isn’t making metal or otherwise showing signs of age.
Obviously, if I buy a set of pistons and start pulling jugs it’s kinda up in the air what the inside will look like. It could be fine, and I install my new pistons and go have fun with my (relatively) cheap 10 HP upgrade. The alternative is that things look not so nice inside, particularly the cam and lifters.
In this hypothetical, let’s assume I pull a jug and find the cam is shot. At this point a case split seems inevitable. The question now is how to proceed. Unfortunately, I do not have any of the logs for the engine before the builder of my plane bought it in the 80s. As best I can tell, it was pulled from an Apache at 200 odd hours and then rehung on my RV-4. I can’t say what run it is.
As I see it, option 1 is to overhaul it entirely and work with what I got. This option includes either sending it off or learning to overhaul it myself. It seems this will probably be the highest cost option.
Option 2 would be an IRAN depending on how everything looks. Take it apart, clean it up, replace seals and toss it back together. Given the age of the engine it will probably end up close to a full overhaul.
Both options 1 and 2 provide the opportunity to properly convert the case to long stud and use hold down plates per the book.
Option 3 would be to get a replacement engine and sell/trade mine as a core. A mid-time engine could end up being the cheapest option, or it could end poorly given the “Pandora’s box” that are used (but not run out) engines. This option is complicated by the fact that I have a conical engine mount, limiting myself to attempting to find another ancient 320.
Are there options I’m not considering? Really all these problems can be solved with money (which makes it not a problem, right?) but I’d appreciate the opinions of others who have perhaps done this calculus before.
Obviously, if I buy a set of pistons and start pulling jugs it’s kinda up in the air what the inside will look like. It could be fine, and I install my new pistons and go have fun with my (relatively) cheap 10 HP upgrade. The alternative is that things look not so nice inside, particularly the cam and lifters.
In this hypothetical, let’s assume I pull a jug and find the cam is shot. At this point a case split seems inevitable. The question now is how to proceed. Unfortunately, I do not have any of the logs for the engine before the builder of my plane bought it in the 80s. As best I can tell, it was pulled from an Apache at 200 odd hours and then rehung on my RV-4. I can’t say what run it is.
As I see it, option 1 is to overhaul it entirely and work with what I got. This option includes either sending it off or learning to overhaul it myself. It seems this will probably be the highest cost option.
Option 2 would be an IRAN depending on how everything looks. Take it apart, clean it up, replace seals and toss it back together. Given the age of the engine it will probably end up close to a full overhaul.
Both options 1 and 2 provide the opportunity to properly convert the case to long stud and use hold down plates per the book.
Option 3 would be to get a replacement engine and sell/trade mine as a core. A mid-time engine could end up being the cheapest option, or it could end poorly given the “Pandora’s box” that are used (but not run out) engines. This option is complicated by the fact that I have a conical engine mount, limiting myself to attempting to find another ancient 320.
Are there options I’m not considering? Really all these problems can be solved with money (which makes it not a problem, right?) but I’d appreciate the opinions of others who have perhaps done this calculus before.