08-10-2019, 02:59 PM
Hi Tom,
I know we all like doing this putting our own bit of magic into the engine but frankly it doesn't make any difference. Flow bench testing has shown that the port is if anything already too big. If it's running OK as it is I'd be tempted to leave it alone, especially if you're wanting to do it insitu but taking the wing off? At most three angling the seats with a bottom 60 degree cutter to narrow the seat is about as far as you need to go and could be just about done without taking everything out. I tried building the ports on one of my engines with plastic metal as they did in the 750 days, even with a twice blasted port I subsequently found a bit missing though it seemingly hadn't done any damage. If you're wanting a bit more; try the things Jack French advised in In Sheeps' Clothing, it's a good read.
Dave
I know we all like doing this putting our own bit of magic into the engine but frankly it doesn't make any difference. Flow bench testing has shown that the port is if anything already too big. If it's running OK as it is I'd be tempted to leave it alone, especially if you're wanting to do it insitu but taking the wing off? At most three angling the seats with a bottom 60 degree cutter to narrow the seat is about as far as you need to go and could be just about done without taking everything out. I tried building the ports on one of my engines with plastic metal as they did in the 750 days, even with a twice blasted port I subsequently found a bit missing though it seemingly hadn't done any damage. If you're wanting a bit more; try the things Jack French advised in In Sheeps' Clothing, it's a good read.
Dave