Got my M5 back after completing its engine swap from J1A5D to B4B5. Completed a 2.5 hour break-in flight, then 2.5 hour flight home.

Haven’t flown the B4B5 before and have been surprised at the CHT spread: low speeds 65% 1&2 @ 300, 5&6 @ 400. At 75% spread narrows down to about 1&2 @ 380, 5&6 @ 420.

Baffling is all new to Maule design. OAT at 10C so the back is running hot and the spread is more than I think it should be.

What are you folks that are running the B4B5 seeing typically?

Kirk

Keep in mind, during break in, the whole idea behind doing it is using the higher friction the rub the apex of the cross hatch down flat. This necessarily produces a lot more heat. It could be that your hot cylinders are just not broken in yet, while the cooler ones are. I don't think you should be running very long down in the 65% power realm during break in, but I could be wrong. Fly it full throttle and hard. Get those ridges worn down. If you mess up the break in, you could be looking at high oil consumption.

Following Lycoming SI 1427C on break in. Most of the time at 75% with some at 65% as per the S.I. Initial 2.5 hour break in flight went well, you could see the CHTs drop off after the first hour.

7 hours on the new engine now, still running mostly 75% and plan to the first 25 hours. The concern is the difference between front and rear cylinders. Specifically, is this an issue with the B4B5. The rear baffle has a different shape than my previous installation.

Kirk

I stand corrected, sorry. Can't help with your original question. I just wanted to give you hope, that break in May not be complete on some cylinders, and they may get within range in a few hours. Good luck

Thanks though, my hope for break-in temps like you suggested has dwindled. It’s got me scratching my head now.

Previous engine only had a single cylinder EGT/CHT so I have no baseline to compare this to. The new setup sure pulls strong though!

Kirk

I long for yesteryear when everyone flew in the red fin, nobody knew their Temps and we were all happy. I curse the day I Installed a jpi.

Capt Kirk,

I have the IO-540-W motor and see about a 40 degree spread in the climb and a 30 degree spread in cruise. My coolest and hottest match yours. I have been told that the #5 is the hottest because of the large hole in the rear baffling for the oil cooler. Not sure I buy that completely because even when I cover the hole in the winter time, the #5 temps don't come down by much. Either way #5&6 are fairly close and by far the hottest.

I can't speak to your 100 degree spread but like you said, I would start with the baffling. (I'll look to see if I have a picture of mine) and then look at indication issues before I starting tearing in to expensive stuff.

Tim

Thanks Tim, 40 I can live with, 100 just ain’t right! Only thing I see to improve the baffling is run high temp silicone bead along the gaps at the rocker covers and 1 small 1/8” gap in the 90 degree bend in the seal.

Weather permitting, I will get it up tomorrow and check it out more. The 100 degree spread was at 75% and 2400 RPM which also resulted in high EGT pretty much across the board. Still getting to know this engine and break it in at the same time but think it likes 2200 RPM better.

Talking with someone else about the EGT now and have a suggested test profile to see if it is set up too lean.

Kirk

I have put 3100 hrs on my B4B5. Two major overhauls and one IRAN. If you want give me a call and I can discuss a few things I have noticed.
406-949-5709 Rick

Can't help you with your CHT problem but im curious why you swapped from the J1A5D to the B4B5?

Not great pictures and since taken i have done them all in silicon. I will be changing the oil and doing some pre-annual stuff next week after my work trip and will take better pics. If there is a specific angle you want let me know.

Tim

montana maule wrote: ↑

Mon Feb 12, 2024 4:24 pm

I have put 3100 hrs on my B4B5. Two major overhauls and one IRAN. If you want give me a call and I can discuss a few things I have noticed.
406-949-5709 Rick

Thanks Rick!

That would be great. I’ll call you tomorrow.

Kirk

Hey Kirk, I'd also like to know how the process was switching from the J-series to the B4B5 engine. My J-series is due for overhaul in the next year or two and I'm considering options.
Thanks,
Paul

UPDATE:

Feeling a lot better about how this engine is behaving and how to run it. Had a great talk with Rick Geiger (Montana Maule) who has a lot of time on the B4B5. He had 1 engine run hot on the back cylinders for about 50-100 hours. Mine were much closer to normal on the next flight.
Next, I tried running at lower RPM (2200) while still pulling 75% for break-in. Everything evens out better at the lower RPM.
Rick also pointed out the “economizer” feature on this carb which adds a richer mixture at full throttle operations. Pulling back just a bit gets the EGT spread more uniform.
Also got another 2 hour flight in including doing a GAMI LeanTest Profile for Savvy Aviation’s analyst to review. I signed up for their SavvyAnalysis service to see what it was like. It is very helpful for interpretation of data and features trend monitoring.

So, a few of you asked; why swap to the O-540-B4B5? I had planned to wait a bit to see how things turned out before doing a write up.
Here are the basics. About 2 1/2 years ago I decided it was time to overhaul the O-540-J1A5D. It was original to my 1977 M5 and had a bit over 2,000 hours. When I bought the airplane, 19 years ago it had 1,000 hours, lots of cylinder pitting from sitting and probably some worn down cam lobes. But it ran reliably, using 1 quart/4-5 hours which never changed. The produced power was getting noticeably lower the last year or two. So, it was time.

I priced overhauls with some major shops but decide to do an exchange with Lycoming for a factory reman through AirPower. Not having the airplane down the whole time it took to do an overhaul was a factor but the deal maker was that Lycoming will allow a dissimilar exchange for no extra charge if you have the dual mag. The engine you choose must be on the type certificate for your aircraft or STC’d.

I don’t think the D mag is that big a deal for reliability, data doesn’t show a higher failure rate. But it does seem like a weak link. Lycoming also includes roller tappets and single electronic ignition at no extra charge.

My options were the J3A5, which is pretty close to being the same as the J1A5D or the B4B5 which is a lower compression and higher RPM engine that can run on auto fuel. The auto fuel STC is available from Maule Flight and cost me $2500 in parts. At the time I made the decision, fuel prices were high and rumblings about unleaded mandates were just beginning.

From a simplicity aspect, the J3A5 would have been easier. The uncertainty about future fuel cost and availability tipped the scales to the B4B5. At the time, it was a 6-8 month lead time to get an engine from Lycoming after placing the order. Rick just told me they are now talking 14 months or more… Good news is you can keep flying while they build it. That’s a long wait though and don’t know if I could live with that.

I’ll post some more about the project in the next few weeks. Things turned out well with it.

Kirk

Good information Kirk, thank you.
PB