rv969wf
Well Known Member
First of all I have mostly built water cooled race engines and a few air cooled engines. My question: Does anyone know the best / optimum CHT to operate a Lycoming IO-360A1B6 Angle Valve 200HP + with 10:5:1 compression. Reason I'm asking this is because this engine has CHOKED / tapered cylinders up towards the combustion chamber. The reason for the CHOKE is to bring the cylinder bore up to the size of the rest of the cylinder at operating temp because the top of the cylinder expands more than the bottom. One example is a Cont..520 series cylinder which will expand 19 thousandths at 475F degrees CHT and at room temp the top of the barrel is 6 to 8 thousandths smaller than the bottom. I'm aware that the CHOKE is the first thing to wear out on a cylinder. Cold starts is a killer on the CHOKE area in the cylinder along with ring and piston ring groove wear issues. I have talked to Lycoming / engine builders XYand Z and I get every answer in the world. I've been told anywhere from 325, 375, 425F CHT is when the cylinder is true and straight. Jeeze that's a 100F spread and 100F variation can make a few thousandths difference, which is best?? I'd like to hear some feedback from Experienced engine builders / pilots that have good hard data and not a thread return like: (Well I run mine at 325F or I run mine 425F with no problems). If I split the 325F and 425F I'm at 375F. I'd just like to know what is Ideal for maximum cylinder, ring, piston ring groove life. Thanks AJ
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