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HIO-360 Helicopter engine in an RV-6A?

SC flyer

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I recently looked at an RV-6A for sale which has an HIO-360-B1A engine with a little under 1300 hrs SMOH. I believe the engine previously came out of a helicopter. I have no prior RV experience but this seems a little odd to me. What info I've been able to find indicates that the primary difference between the HIO-360 and the IO-360 is that the HIO redlines at 2900 RPM vs 2700 RPM and the TBO is 1500 instead of 2000.

Anyone out there have experience with these engines? It's nearly at TBO now and an overhaul would likely cost about the same as on the IO-360 but would only provide 75% as much usable time afterward. Doesn't sound like a very good idea.

Any idea how much to replace it with an IO-360 at overhaul time? Other options? Thoughts?

I would expect the low tbo is due to the high rpm limit and the heavy use in a copter. If most of the 1300 hours are in the RV, I would expect a tbo of 2000 hours, and fly right past that as long as the motor passes it's physical.

Understanding Lycomings requires you to read from the bottom up. Find your model here and follow the hints printed in the statement to check compatibility and differences.

Power rating is different for helicopter engine vs aircraft use.
HIO-360-B has a rating of 180 HP at 26.1 Hg. manifold at standard sea level conditions to 3900 feet standard altitude with 25 in. Hg. manifold pressure.
As it has a compression ratio of 8.7 you could expect 190 hp at MSL 2.700 rpm.
TBO would be related to operating conditions, expect 2.000 hrs.
Most parts would be the same.


Good luck
I just installed an HIO-360-B1A in the biplane I built but converted it to Dyna focal mounts and carbureted. It doesn't bother me a bit, in fact, if you look at the weight of that engine, it is about the lightest of the O-360 variants that Lycoming builds. Where did you hear about the 1500 hr TBO? I don't recall coming across that, but it wouldn't have concerned me, since I'm planning on spinning mine up well beyond the 2900 rpm limit anyway. It should be 8.5:1 compression, right? I see no reason to replace it with something different.
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As Gasman suggests, the lower TBO is associated with the higher RPM's required by use in helicopters. The HIO-360's I used to maintain were all in the HU300 series helicopter and the primary issue we experienced was fretting of the Center Main Bearing. The higher RPM's seemed to make this a weak point. If an operatror was unlucky he might find the Center Main Bearing had spun in the journal - I saw many of these occur - but almost all engines needed rework at overhaul in that area.

Running that engine in your RV at a max RPM of 2700 shouldn't result in the same kind of problems though.
Helicopter engine installed in RV6

My RV6 has an engine that came out of a helicopter at 1,000 hours since new. ENG: LYC O-320 B3C; 160 HP Wide Deck Engine.
Performed a top overhaul and it’s now approaching 2,000 hours on the bottom end. It runs strong & oil filter pleats are clean as a whistle.