Going with IO-390 for M20E. 2-blade prop or 3??

[bdjohn4]

Had a prop strike on an 1800 hour high-time engine (IO-360A1A). Turns out it was an omen. The internals were looking terrible (most certainly from long before the strike, with camshaft that shed bits of metal into the cylinders. Looked horrid) and I am told the prop governor was not long for this world. So, that is how I am rationizling my mistake that lead to the strike.

 

So, the price of an IO-390 A3A6 was only slightly more than a IO-360. Therefore, I am going to go with that. Lycoming seems motivated to get more of us Mooney drivers to consider the swap. When you go with IO-390, you have to buy a new prop-governor anyway, so that is $$ I'd have had to pay anyway if I went with that.

 

Now, with a high-time old beater motor in my E (3-blade top prop conversion, 201 winshield and some gap seals [tail, dorsal, flap, LASAR cowl enclosure, smooth belly]), I was getting a TAS of 150-151kts. my main question is, what can I expect with a 2 blade vs a 3 blade. I read that MAPA PIREP a few years ago of the guy in the upper midwest who was dissatisfied, but noted that the experiments were not carried out with much scientific rigor (i.e., he usually was at X thousand feet before he got to the edge of the lake, but now, with the IO-390 he was only Y thousand feet). I didn't know what to make of that. The Glastar Sportsman article featuring a head-to-head comparo of the 360 vs 390 seems more valid, and shows significant performance increases.

 

The approved Hartzell prop is a blended airfoil design, which I can't say would change performance much based on what I read on the Van's Airforce site of a guy that had a long conversation with the Hartzell engineers, but certainly would look cool.

 

Anyway, your thoughts would be appreciated on which number of blades to buy. I have to decide which prop to order soon.  FYI: I fly out of a 5000ft paved runway in the SE at 600ft MSL and do a lot of long X-crty trips. Monroy tanks installed too.

bdjohn

[bdjohn4]

IO-390 A3B6. Oops.

[DS1980]

From what I understand from other threads, you'll climb quicker with a 3 blade but cruise faster with a 2 blade. General statement from someone who has no experience with a 3 bladed Mooney, so you know I'm legit!

 

What's the reason for Lycoming wanting to sell the 390? Larger profit margin?

[John Pleisse]

Can you even put a 3-blade on the IO390? It was my understanding the IO390 was only approved for the 2 blade Hartzell Top Prop. Your E is going to scream and you'll love your upgrade.

[jetdriven]

The IO-390 STC only allows the blended airfoil Hartzell 2-blade prop.    I looked at it, but an additional ten grand for a prop put it out of our price range.  The IO-390 is also limited to 210 HP for 5 minutes, after that, 27.2" MP and 200 HP continuous.  So at altitude you get 75% of the extra 10 HP, or 5-7 HP at cruise.

[Dale Logsdon]

My bud's IO360 was overhauled by a custom rebuilder and was dyno tested producing 225 HP. Cheaper than a io390.

[Hank]

John,

 

Looks like your speed mods will balance out the 3-blade drag. My C has the guppy mouth closure, 201-windshield and wingtips, and a Hartzell 3-blade. I turn in book speeds in my 1970 Owner's Manual. From what I have read about the 390, I have no opinion, but I wish you luck. Please gather good data afterwards!

[KSMooniac]

Byron is correct about the 2-blade Hartzell BA prop being the only option.  I would choose it 10 times out of 10 over any metal 3-blade prop anyway if your goal is speed.  Climb in any E will certainly be good no matter what prop you choose.

 

My bigger concern is the cost of ownership with the IO-390.  As I mentioned in the other thread, those cylinders are $4000 each, and if you have another prop strike you'll have to replace the roller lifters by decree instead of on condition, and they are expensive as well.

[rbridges]

I don't know if you've researched it, but IIRC, the cylinders for the 390 are crazy expensive.  Something to keep in mind if you have to replace a jug.

 

edit--I see Scott already mentioned that.

[John Pleisse]

Well also, you'll have a significant weight increase with the Top Prop. Quite a bit on a short body, eh?

[OR75]

I am curious about the price difference between a 360 and a 390

I looked at the option just a few weeks ago and the price difference significant ( 10-15 amu)

Not including the prop

[KSMooniac]

At first glance, the cylinders are $2k more each, and the roller lifters are a lot more expensive...pretty easy to get to a 10 AMU difference right there.

[jetdriven]

We looked at it a year ago and the factory OH IO-390A3A6 engine was only a grand or two more. That prop is the deal killer, that turns a 35K job into a 45-47K job.

[carusoam]

Makes putting an IO550 in make sense again... Ask Seth...

Best regards,

-a-

[OR75]

We looked at it a year ago and the factory OH IO-390A3A6 engine was only a grand or two more. That prop is the deal killer, that turns a 35K job into a 45-47K job.

I am curious of where you got that quote

Quotes I saw where about 55 amu with prop. So about 45 for just engine swap.

The install of a 390 must be done by a Lycoming authorized service center. It is an STC. So you cannot just go to airpower and order one for your ap to swap

Or maybe i did not shop around enough.

[jetdriven]

Wayne said we could probably install it ourselves but pay them for the STC. The IO-390 in a box with core exchange etc was about the same price as an IO-360, but the prop made it too much.    55K laid in is insanity, you got yourself an airplane worth 3K maybe 5 more than on with the IO-360 but paid 20K extra to get it

[Jamie]

I have a low time 390, and you guys keep scaring me with the $4000 dollar cylinders.

 

I wonder if it would make sense to have the engine taken off and replaced with an IO360 of similiar vintage?

[jetdriven]

Take care of it and it will last. If you have one go bad, have it reworked.

[OR75]

Wayne said we could probably install it ourselves but pay them for the STC. The IO-390 in a box with core exchange etc was about the same price as an IO-360, but the prop made it too much.    55K laid in is insanity, you got yourself an airplane worth 3K maybe 5 more than on with the IO-360 but paid 20K extra to get it

exact footprint and hoses/brackets than for the IO-360-A3B6 so i am sure any A&P can do the swap.

but how much for the STC ?

not too worried about the cost of cylinders and parts. the 390 is widely used in the experimental pool.

[fantom]

Just treat that engine and those cylinders very well.

 

I have a low time 390, and you guys keep scaring me with the $4000 dollar cylinders.

 

 

[kmyfm20s]

Have your IO-360 rebuilt and have Ly-Con overhual, port/polish and flow balance the cylinders and you will be ahead of the IO-390. I have just finished breaking in my overhauled cylinders from Ly-Con and can feel the difference. I hope to have some numbers for a PIREP soon but with the increased fuel burn I've been seeing with the full rich, full power break in and some of the top TAS can only mean more power! I need to get more precise with my data collection then I will post it but so far I'm impressed!

[bdjohn4]

Wow, this generated a lot of interest. Aware of the cylinder costs. The more IO390s that get out there, the lower the cost of cylinders will be in the future. I'll take my chances. Having an IO-360 ported/polished/flow-matched is great, but that alone would probably be as much (or more) than the cost differential between the IO360 and the IO390, and if I want I suppose I could have the same done to the 390, I suppose. I have to buy a prop/prop-governor anyhow, so the $s end up working out fine. Like I said, Lycoming was VERY willing to work with me on pricing a reman IO-390A3B6, and it was only a few thousand more than if I rebuilt my old IO360A1A (a very old design indeed), so I happily chose the reman 390.  Hopefully you guys will consider this option too when the time comes. Also, hopefully the 2-blade Hartzell prop matches well with the motor.  We'll see I guess.

[kmyfm20s]

Port/polish/flow matched $300 additional per cylinder. They claim 4 to 5 hp per cylinder. Just an option that you could indeed do with the 390. What is the weight penalty for the 390 vs 360? Prop?

[KSMooniac]

I'll be interested to hear your reports after you fly it.  It does seem like a good choice in your instance if you needed to buy a prop and governor anyway, and the newer technology engine will certainly be nicer than the old -A1A engine.  

 

Don't count on the cylinder cost going down, ever.  The Lycoming angle valve cylinders for the "regular" engines are sole-source Lycoming and their prices have only gone up over the years.  If the aftermarket won't make any of those cylinders, they surely won't make any -390 cylinders either...

[bdjohn4]

Not sure exact weight penalty for engine. I heard 30 lbs but that was a back of the napkin statement and we weren't sure if that was applicable to the IO360A1A or a number from another model.Looking at Lyc's website:

http://www.lycoming.com/Lycoming/PRODUCTS/Engines/Certified/360Series/EngineData.aspx

They are saying an A-series IO-360 is 325 lbs (with the 360ci engines varying wildly in weight for some reason) and an IO-390 as 308 lbs?!?! I don't know if that is an apples/oranges thing or what.

 

I am going from 3-blade to 2-blade so even if the "real" IO-390 is a tad heavier, with the lighter prop it should be close to a wash.

 

If a port/polish is that cheap, maybe I should have them do it on the 390 at instal    I'll ask if that is doable. 220HP with the Powerflow??

JML