YIO-360-A1B6 Question

Hi all,

I'm going through the Non-Certified Lycoming order form and interested in the YIO-360-A1B6 for the extra 20 HP (compared to the M1B) but wondering why the order page says it can only be fit with a C/S prop?

If I'm not mistaken, any engine with provisions for a C/S can have a fixed pitch on it, and 200 HP isn't too much for, say, a Catto prop.

Also curious where the 20 HP comes from. Basic research tells me it's a tuned induction system for an increased compression ratio of 8.70:1 vs. 8.50:1 on the M1B. For $6k, I'm wondering what I can tune myself to irk out the higher 0.20. I'm already planning for EFI.

Happy to learn - I've put an email in to Van's as well.

Welcome Schuyler.

360-A is an angle valve head. Slightly domed combustion chamber, better port angles, higher combustion rate. Externally, cylinder finning is more extensive; easier to maintain cool CHT. Case has piston oil squirters, so generally more oil cooling capacity required. Crank has pendulum absorbers, aka counterweights, which eliminates a bunch of prop restrictions. Weight is more, engine about an inch wider.

Typical power from the 360-A is closer to 195 than the rated 200.

BTW, the parallel valve M1B has the same intake plenum and tuned intake.

Thank you, Dan! That helps a lot.

You're welcome.

If you really want fixed pitch, just go with the lighter parallel valve. The Vans Lycoming deals are excellent, but there is also the 370/375 option from Continental Titan, a parallel valve stroker available with or without pendulums.

That's what I'm thinking. The angle valves might also be more complicated to overhaul and install an EFI into - since that might require sculpting of the cylinders.

Lycoming responded regarding this. The A1B6 can be converted to a fixed-pitch configuration, but it is factory-configured for constant-speed only.

Conversion to fixed-pitch would need to follow these instructions.

For a mere $800 more you can have an IO-390! Just saying...