[craigw85]

Hello RV'rs! I'm a new adopter of a wonderful RV-6. With my new (to me) airplane (that's getting painted at the moment) came a Lycoming engine manual. I'm trying to figure out exactly which of the many engine graphs apply to my aircraft. I see there is a difference between an IO-360-M1A and IO-360-M1B engine in the charts. Looking at the placard on the engine, this is what I see:

Aero Sport Power IO-360-M1
Eng. No. 0546-SP
Fuel-Oct Min: 100LL
Normal Rated: 180 H.P. AT: 2700

What is the difference between the M1A and M1B?

Thanks guys! (and a shoutout to the many wonderful RV'ers in the socal area that made my dream of owning an RV a reality!)

--Craig

 

[Tracer 10]

Difference between M1A and M1B

Kevin Horton
04-02-2007, 08:41 PM
Start with the big picture, and ask yourself a few basic questions:

1. Do you want a heavy, 200 hp, angle-valve engine, or a lighter, 180 hp, parallel-valve engine? The IO-360-A series engines are the heavy, 200 hp, angle-valve ones. The IO-360-B and -M series engines are the lighter, 180 hp, parallel-valve ones.

The IO-360-A series engines have the fuel injection servo on the front of the oil sump, and they get the smooth front lower cowling.

2. If you want the 180 hp engine, where do you want the fuel injection servo? If you want it on the bottom, with the induction air inlet in a scoop on the lower cowl, then you want an IO-360-B series engine. If you want the smooth front lower cowling, then you want one of the IO-360-M series engines.

As to the difference between an IO-360-M1A (no such thing as an IO-360-M) and an -M1B, you should be able to find that on the FAA Type Certificate Data Sheet. Go to the FAA Web site (http://www.faa.gov/), click on Licenses & Certificates (http://www.faa.gov/licenses_certificates/), then click on Type Certificate Data Sheets (TCDS) (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/MainFrame?OpenFrameSet). Type "IO-360" in the Search box, click Go, and look for a result from Lycoming. The crazy FAA web site will then give you a quick web IQ test, as it presents you with a useless series of pages, each with a magic link that you must find to get to the next page in the series. The FAA will eventually tire of this game, and one of the links will actually give you the TCDS. I won't put the URL here, as they seem to change them every few days, just to drive us normal folks nuts.

Once you are in the TCDS, look for a section near the end that lists the differences between engine models.

 

[WenEng]

Main difference...

?....What is the difference between the M1A and M1B.....
--Craig

IO-360-M1A = Similar to IO-360-B1E except front inlet fuel injector, prop governor on front of crankcase and retard magneto.
IO-360-M1B = Similar to IO-360-M1A except has a rear mounted propeller governor and impulse magneto.