Io-390

[Bret S]

Originally Posted by Kahuna

I flew some hours off an 8A with the 390 and I was not impressed. Builder mentioned there were no material install issues.
Im still a firm believer that the parallel valve 180 is the way to go on the 8 using a four banger. I have 2 guys I fly with with the 200hp angle valve and they both wish they went with the parallel valve. The 20 hp is not worth the extra weight.
My 2 cents.
best,

Can we try and quantify how much lighter?

Looking at the Lycoming figures for engines it seems IO-360-M dry weight is 300 lbs and the IO-390-X is 308 lbs (not much difference) assuming normal compression and fuel injection. I would guess between 20-30 hp for 8 extra lbs sounds good. Choice of propeller will greatly affect total weight. Wood props 20 lbs and metal CS will be about 55 lbs.

To get lighter you may need to use an O-360-A series then get 285 lbs.

Range of weight:

low end O-360-A with wood prop = 305 lbs for 180hp
high end IO-390-X with CS prop = 363 lbs for 210hp

Is this what we're talking about?

[DanH]

I have a 390 on order from Barrett, so obviously I don't think it is a poor choice. Previous angle valve 360 -8A experience tells me that stick forces and response in the -8 will be heavy at solo, full fuel. However, it goes away with something in the back, and I loved the power. So, this one gets Grove gear, rear battery, and no prop extension. I'll take the forward CG "penalty" in my Sunday fun flights in return for the power advantage when loaded with bride and baggage. That's the prime mission for this airplane.

Kahuna, gotta pull your leg a little bit....you have a 6-cyl in your own RV-8, but an IO-390 is bad? <g>

[Kahuna]

Originally Posted by DanH

Kahuna, gotta pull your leg a little bit....you have a 6-cyl in your own RV-8, but an IO-390 is bad? <g>

Yep it is. Ill take that weight penalty for the power given. (6vs4 cyl.)
I would not take the weight for the power of an angled valve over parallel.
Yes I think the 390 is bad in comparison to a parallel 180. I have done head to heads. Parallel wins on climb and I have never experienced a material speed difference between the parallel and angled engines on the RV-8.
my 2 cents.

[N62XS]

I have an IO-360-A1B in my RV-8. The next one will have a parallel valve 180HP, "tweaked"(ported, polished, balanced and blueprinted, custom exhaust, CA Sump, small compresion bump) to get to 200HP. The difference I see in the angle valve is climb. It climbs better, longer and faster than the 180HP airplanes I have flown/flown in. One more thing that is often overlooked, CHROME MAKE EVERYTHING GO FASTER!

[Mel]

Another minor point; The parallel valve engines come out ahead in the "bullet proof" department. I see many more cracked cylinders on the angle valve engines.