I am requesting input from all of you that have knowledge in the area of putting 9:1 pistons in a low compression (150hp) O-320. The answer below from Sacramento Sky Ranch (www.sacskyranch.com/lycoming.htm) indicating that if you do not have nitrided cylinders (which I do not) it is a bad idea. Others who I trust say "it is not a certified engine, it is not going to hurt anything on a wide deck as long as you don't go above (9:1).
Really curious as to what all you smart people have to say.
Sacarmento Sky Ranch article below.
What is the difference between one Lycoming engine model and another
The "Same Engine" Myth
Questions that frequently are asked of Lycoming sales personnel, engineers, and technical representatives indicate that there is a myth regarding Lycoming piston engines. This myth seems to be prevalent among aircraft owners and aviation writers. In the minds of these individuals, each Lycoming engine series is essentially the same. For example, all 360 cubic inch displacement engines are inherently the same except for differences in fuel metering or turbocharging. The idea that these engines are the same is false. A few specific examples may help to put this myth to rest.
Lycoming builds 0-320 engines that produce 150 HP or 160 HP. The 150 HP O-320-E series engines operate at a compression ratio of 7.0:1. The 0-320-D series has high compression pistons which raise the compression ratio to 8.5:1, and increase rated output to 160 HP. Those who believe that the pistons are the only difference in these engines will be disappointed when they plan to upgrade their 0-320-E to the higher horsepower by simply changing pistons. Many models in the 0-320-E series were designed for the purpose of keeping the cost down. Thousands of these low compression engines were built with plain steel cylinder barrels instead of the Nitrided barrels used in the 0-320-D series engines. They also had two narrow bearings instead of one long front main bearing. The engines were certified at 150 HP and were not intended to withstand the additional stress of higher horsepower.
Really curious as to what all you smart people have to say.
Sacarmento Sky Ranch article below.
What is the difference between one Lycoming engine model and another
The "Same Engine" Myth
Questions that frequently are asked of Lycoming sales personnel, engineers, and technical representatives indicate that there is a myth regarding Lycoming piston engines. This myth seems to be prevalent among aircraft owners and aviation writers. In the minds of these individuals, each Lycoming engine series is essentially the same. For example, all 360 cubic inch displacement engines are inherently the same except for differences in fuel metering or turbocharging. The idea that these engines are the same is false. A few specific examples may help to put this myth to rest.
Lycoming builds 0-320 engines that produce 150 HP or 160 HP. The 150 HP O-320-E series engines operate at a compression ratio of 7.0:1. The 0-320-D series has high compression pistons which raise the compression ratio to 8.5:1, and increase rated output to 160 HP. Those who believe that the pistons are the only difference in these engines will be disappointed when they plan to upgrade their 0-320-E to the higher horsepower by simply changing pistons. Many models in the 0-320-E series were designed for the purpose of keeping the cost down. Thousands of these low compression engines were built with plain steel cylinder barrels instead of the Nitrided barrels used in the 0-320-D series engines. They also had two narrow bearings instead of one long front main bearing. The engines were certified at 150 HP and were not intended to withstand the additional stress of higher horsepower.
