Don't worry about it
RV4er said:
I have a narrow deck O-320 w/o the cylinder hold down plates that has been converted to 160hp. In researching STC?s for this conversion, the ones I have found are for the wide deck O-320?s only. Now I?m beginning to have concerns whether I should change my engine back to 150hp or not. Do any of you have the narrow deck 160hp and if so what has your experience been?
Well if it is done, done right, leave it alone is my advice. What I'd recommend is modify your operations a little if you are worried, such as only use full power sparingly, meaning limited time on takeoff or climb only; than either throttle back or don't fly WOT below say 3,000 feet. At 3,000 feet and above you would be should be well below 150 hp.
In a nut shall manually limit the HP to 150 with the throttle, verses lowering the compression. A little full power 160 HP is not going to kill it. Personally I would not ring-it-out racing WOT at sea level for hours. However that's my conservative attitude. I know a lot of narrow decks get bumped up and heard of no big issue. As long as the power is lower (manually) the stress should be similar as if the compression was lower, ie 150 hp.
If done properly, meaning the cylinders have the right choke and so on, than it should be fine; don't worry about it. Obviously a STC does not mean goodness, or I should say lack of STC mean its not acceptable. We just don't care about STC's but it is a good idea to research and find all the info you can.
I'm not sure if there's a narrow deck STC for 150 to 160 hp bump. However I do recall some of the 160 HP STC upgrades listed a max power time limitation. Thats where I got the idea of manually reducing power with the throttle hand. I had the same choice with a O320 narrow deck and decided to stay with the 150 HP, but I did not see a big issue at the time.
Last suggestion, keep an eye on it and do good maintenance, like regular oil changes and keep the temps (CHT/OilT) in limits. You may want an occasional oil sample analysis base line and than every other. If it ain't making metal, than it'll give you even more confidence your engine is healthy. There's nothing wrong being a little paranoid. Good Luck, G
