M7 235 vs M7 260 Engine horsepower

210TC · Post by **210TC** » Sun Mar 28, 2010 7:12 pm

BTW: How did you get to be a fourth generation Alaskan? I thought Alaska was to young for that.

BUZZ · Post by **BUZZ** » Mon Mar 29, 2010 12:17 am

I guess technically so. My great grand dad was born near fairbanks in 1911 well before Alaska was a state, but still Alaska. His dad came up in the mid 1890's and eventually moved the rest of the family up. Can't imagine being anywhere else.

Kirk · Post by **Kirk** » Mon Mar 29, 2010 2:49 am

a64pilot wrote:There a lot of internal differences between the 260 FI and the 235 FI. Be careful of turning up the prop governor in the 235 too much in the quest for power, it's not made for it.

Very true! This, among many other questions is addressed in Sacramento Sky Ranches FAQ section:

http://www.sacskyranch.com/lycoming.htm

Kirk

210TC · Post by **210TC** » Mon Mar 29, 2010 6:57 am

COOL, I bet very few exist with your roots. sounds like you have a strong family. When my family grew up we went all different directions.

akholland · Post by **akholland** » Mon Nov 02, 2015 11:10 am

can someone please elaborate on the comment about the governor on the 540. will it blow a prop seal or something if it's turned up too high?

Andy Young · Post by **Andy Young** » Mon Nov 02, 2015 12:49 pm

I'm guessing that what that's about is just trying to get too power out of the 235 engine, and thereby stressing the mechanical parts beyond design limits. The 235 and 260 hp 540s use very different crankcases and crankshafts, as I understand it. The 260 horse parts are much heavier duty, to handle the extra rpm and power. The 235 parts are lighter duty. Some people mistakenly think that they can turn a 235 into a 260 simply by spinning it faster, but if one does so, it won't last long...

chris erasmus · Post by **chris erasmus** » Thu Nov 05, 2015 8:54 am

O540 B4B5 engine 235 HP in my Maule. Upped the compression slightly, changed the crank balance weight and a few other things, now at 250 hp. Polish balance and flow engine should add 5 hp minimum
Busy developing a tuned exhaust system for the engine, should gain a further 5 to 10 hp.

Hope to end up with 270 hp in the end and an engine that can run on mogas all day long, desperately need the horses for our hot and high conditions in South Africa

akholland · Post by **akholland** » Thu Nov 05, 2015 9:19 am

what part number crank balance weights did u use and what compression

chris erasmus · Post by **chris erasmus** » Thu Nov 05, 2015 9:29 am

Don't know the technical details, the engine guys took care of all of that, compression went from 7.3 to 8.1

akholland · Post by **akholland** » Thu Nov 05, 2015 11:53 am

Oic. my j1a5d should already have 8.5:1 I'm pretty sure the b model has the heavier counterweights Than the j model which gives the higher rpm rating, not sure though

captnkirk · Post by **captnkirk** » Thu Nov 05, 2015 6:55 pm

https://www.bing.com/videos/search?q=ho ... B86023BD21
ok you guys got me thinkin

akholland · Post by **akholland** » Thu Nov 05, 2015 7:08 pm

U saying my hot rod Lincoln would run low on gas and start a knocking... then red lights a blinking and pappy throw my bail?

gbarrier · Post by **gbarrier** » Fri Nov 06, 2015 8:06 am

Come on, we need sunshine. Gotta get out and fly. We're all going a little MORE crazy.

Mountain Doctor · Post by **Mountain Doctor** » Fri Nov 06, 2015 4:15 pm

DonMc wrote:I would not run below 20'' for extended period of time. Especially in cold weather.

DonMc
N260BD

I read a story of a 182 that iced up and had to make an emergency/precautionary landing by Tieton,, Washington.

The theroy was that he iced up from running at a low power setting, and was unable to melt it with full carb heat, presumably due to the engine not making enough power/heat to clear the carb.

If I'm not going anywhere, and just flying around, I see no need to get there (nowhere) fast so I'll run at the bottom of the green, 2,100 RPM. I lean it till it's ready to quit and then a little rich from thee. This keeps the plugs and jugs clean, and the EGT up. At the low power settings nearly impossible to run too lean. Summer CHT under these conditions is low 300's.

akholland · Post by **akholland** » Wed Nov 07, 2018 11:21 pm

So I found a b4b5 o-540 on barnstormers and Im debating upgrading from the j1a5d. I have been working on my j model for 3 years tinkering and I can't make it kick the low rpm shake. Believe it's got a bad crank dampener bushing and I'm in need of a bottom end rebuild. I've changed EVERY part other than the bottom end and oil sump.
Their asking 12k for the motor. 400 smoh.

Can I still run my 86 Mac with the B model? Its a 7.2 compression 235hp at 2575rpm. I'd probably use my 8.5:1 pistons and should get 250hp.

Is this upgrade worth it or should I overhaul my bottom end for 10 to 15k..

M7 235 vs M7 260 Engine horsepower

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