M7 235 vs M7 260 Engine horsepower

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gbarrier
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Post by gbarrier »

The 235, carb or injected is a great engine but from what I can find it is great at 235 hp. I wouldn't push it. I'm not familiar with the carb units but I know that while the injected 235 (W1A5D) and the 260 (V4A5) are totally different. They look alike but the crank, case, pistons (same compression) and cylinders are different part numbers. There is a reason for that as evidenced by the weight difference. Also, from the factory the 260 comes with a 5 point attach mount versus the 4 point for the 235. Again, I'm sure there is a reason.

Go experimental and do what you want but remember "It's your experiment".

akholland
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Post by akholland »

The a models, b models, and j models are the same other than various crank dampers. And obviously the j model is dualmag and derated rpm. There seems to have been a lot of changes made specific to what prop they were running as far as dampners go. I have yet to find information on that though for what's what. The b4b5 came on the m7 235. I have a friend with 10:1 in his j1a5d model and it runs awesome at 2575.

W and K models spin 2700 and I believe have different cranks.

I'm mostly curious if the b4b5 is approved with the 86 Mac or if it's just the j1a5d

Cubdriver
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Post by Cubdriver »

86â€￾ Mac is only approved on the W and J series engine due to the 2,400rpm. The 86â€￾ makes too much noise at anything over 2,400rpm according to the EPA. My close friend and IA applied for and received a field approval to install a 0540-A1C5 “Comanche engineâ€￾ on my M5-235c in conjunction with a 84â€￾ Hartzell two blade propellor. 250hp at 2,575 rpm. Carburetor,Two mags, cheap cylinders, readily/affordable parts. I’ve run it hard now for 3 seasons hauling hunters in my 135 operation. Also modified it too an M6 last winter. The airplane is astounding, I also run a cub on big rubber. Went from flying my cub close to 400hrs in 2 months to barely 75 this last season. Love my Maule, my two cents.

akholland
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Post by akholland »

A local engine builder told me the j1a5d also has lighter rods compared to other models. It also obviously has the light hex crank with lightening holes in it. And the dual mag saves some weight. I'm not sure what's different about the case. Some of guys go 10:1 pistons and run 2575 to help it along and run a 86 Mac. I flew my buddies and my io360d still gets off faster. Wasn't super impressed. He's got a few hundred hours in it and no issues so far. It does climb out really good though

I think the j1a5d would benefit ALOT from a good crossover exhaust and an efii ignition. Problem is making up a single mag to go in the dual mag hole because the gear is different.

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