RV-4 engine thoughts

I have a RV4 under restoration.

As we speak I have a O320-E2A (roller tappets) that would need a rebuild and probably a new Crank(prop strike)

Before I pull the trigger on overhauling this engine I would love to get some inputs from you guys. Here are some thoughts:

+ I was told that I MUST go for a O360. Much faster, climb better and much more fun. My personal observations is that the O320 with 160HP pistons would do almost the same job based on weight/power ratio.
+ I have a strong wish to have a constant speed prop since I will operate out of a short runway. I was told fixed pitch would make the approach much flatter. Since I also would like to use this plane for some light acro, a constant speed is probably the best option.
HOWEVER I was also told that it is hard to find parts to add C/S to a O320 vs a O360??!! I dont know what is in this, but I guess it is either the Gov or Prop or both.

I guess I could live with a bit less climb power as long as the O320 can be rebuilt to C/S. If thats not really possible, then I guess the only option would be to find a O360.


Another issue is that if I go for a O360, I would need to get another bottom cowling, and probably the longer gear struts. So I would really like to keep the O320 and spend my OH money on this one.

I have questions about upgrading to fuel injections too, but I guess we can discuss that in another post.

Espen

I have a 320 in my RV-6 with Constant Speed prop.

I wish I had put a 360 in the RV and as far as RVs that I own, they will be just like the factory and use a constant speed prop. Only the RV-12 has been factory built without a constant speed prop in the last 15-years.

The 320 and 360 use the same crankcase and accessory case. They use the same parts for the constant speed prop. There were some 320's with 4 piece nose bearings that will not accept the CS prop and or course the solid crank will not accept the hydraulic CS prop that most of aviation use.

The pounds of fuel per hour per horsepower produced is lower on the 180 HP 360 than the 160 HP 320. One can always reduce the manifold pressure on the 180 to slow down but one cannot push the 320 to higher HP.

IF your 360 or 320 engine crankshaft, case, and accessory case is setup for CS operation, see Lycoming SI 1435 for the steps needed to concert.

I have never met a pilot that said I wish this airplane had less hp or less thrust. I have heard many justify having less. If you can afford it, I would go with more hp. Personally, I also prefer a CS prop for formation and aerobatics. Can both be done with a FP, yes, but again, I prefer the CS prop.

Do you drive a Corvette or a Prius? Same type arguments, where do you choose to spend your money -- on speed or fuel. If I had to fly a 320 FP or have no RV, I would be flying a FP 320 and I would tell everyone that was the best choice to make!

If you go with gear legs, you also have to have a different motor mount.

O-320-E2A has the nose bearing setup that will work with CS. So the engine you have will work. The engine parts for CS are the same from a 360 or a 320.
Good Luck,
Mahlon

FP 320

I have 500 hrs in an RV4 with a fixed pitch prop and a 150hp O320.

While I agree with others about the advantages of the 360 and CS prop, the plane is certainly no dog with the smaller engine. I've found my -4 to be a very capable and efficient airplane. Short field performance is great, and it has great cruise performance as well.

Some care and attention to the induction system can create a nice CHT and EGT balance, allowing you to run LOP (if your religion permits), so specific fuel consumption of the O320 can be brought inline with the larger fuel injected engines.

For me, managing descents was simply a matter of getting familiar with the airplane. The fixed pitch setup is perfectly capable of smoking into the pattern at cruise speed, slowing down, and completing a steep approach to a short field landing.

The 360 CS setup would be awesome, but the FP O320 is only slightly less so. Frankly, you can't go wrong either way.

M

If the crank on my O320 passes the test, then I will "more or less" have a free engine. Since the E2A is CS upgradable, I really feel that this is the way I should be going.
That would also avoiding having to buy a new lower cowling and maybe a new engine mount and legs to build prop clearance. (Getting big parts to Europe is expensive)
So the money saved could be used on a EFII ignition and injection system.
With the 160hp pistons, it really can't be that far away from a O-360 performance without the upgrades. And the overall weight will be lower.

I agree with Mahlon.

I agree with Mohlon on the engine and would add another tid-bit. I can tell you without any reservation that the most Hp. you can put or get out of the lightest power-plant will be the one you will like the best. I think that the 4 was rated as a 160 Hp. bird. You can rebuild a 320 and get a little more than that out of the same light weight power-plant. I have seen very light 4's with wooden props run away for others with all the goodies you could put on one., just because they were so much heavier than the basic light one.
But it all comes down to what you want and like to have.
Hope this helps, Yours, R.E.A. III #80888

spirit49 said:

I have a RV4 under restoration.

As we speak I have a O320-E2A (roller tappets) that would need a rebuild and probably a new Crank(prop strike)

Before I pull the trigger on overhauling this engine I would love to get some inputs from you guys. Here are some thoughts:

+ I was told that I MUST go for a O360. Much faster, climb better and much more fun. My personal observations is that the O320 with 160HP pistons would do almost the same job based on weight/power ratio.
+ I have a strong wish to have a constant speed prop since I will operate out of a short runway. I was told fixed pitch would make the approach much flatter. Since I also would like to use this plane for some light acro, a constant speed is probably the best option.
HOWEVER I was also told that it is hard to find parts to add C/S to a O320 vs a O360??!! I dont know what is in this, but I guess it is either the Gov or Prop or both.

I guess I could live with a bit less climb power as long as the O320 can be rebuilt to C/S. If thats not really possible, then I guess the only option would be to find a O360.


Another issue is that if I go for a O360, I would need to get another bottom cowling, and probably the longer gear struts. So I would really like to keep the O320 and spend my OH money on this one.

I have questions about upgrading to fuel injections too, but I guess we can discuss that in another post.

Espen

Click to expand...

Take a look at Van's performance spec's on your RV-4 for aircraft with different powerplants. According to them, going from a 160 hp engine to a 180 hp engine adds 8 mph to the top speed and 300-400 fpm to the climb rate. It cuts the takeoff distance by ~50'. I would trust those figures.

Regarding your short strip, how long is it, and at what altitude is it located? Are the approaches clear?

I guess where I'm going is that IF you need the additional performance of 20 more HP and a CS prop, then you should go in that direction. If you don't need that additional performance, rebuilding your O-320 would be (in my opinion) a good choice.

As an aside, a CS prop is not necessary for aerobatics. I've been doing them for 16 years in an O-320/fixed pitch RV-6 and haven't come close to the overspeed worries occasionally mentioned in this space.

Guys.
Thanks a lot for your inputs.

It sure feels like I will go for the OH of the O320.

What about the quote that CS parts are hard to find for the O320 vs O360?
Are we talking about prop or governor? Or both?

Hello Spirit 49,
I won?t argue or debate the 0-320 F/P verses the 0-360 C/S but can talk about my observation of flying a built to plans and unmodified RV4 these past 28 years.

My bird has manual flaps, normal aspirated carburetor, the stock, short legs landing gear with a few steam gauges and was always equipped with a F/P. The 0-320 originally came out of a C-172 at 150 HP and when I overhauled, installed the higher compression pistons for a 160 HP output.

Our flying the past 28 years has been 99% in the Rocky Mountain States with our field located at 5500 MSL. Most of my flying therefore is conducted in the low teens if I want to travel. We have been to back country strips too numerous to mention here, with camping gear for as long as two weeks. I?ll admit the load for camping is more like what you would use for back packing so not for everyone?s taste.

She has competed in a SARL race and placed very well considering the supposed disadvantage of the F/P. You can check out the results for SARL race Pagosa Springs 2015. This was from a standing start so the C/S had the advantage initially but I was closing in on them by the fifth turn.

A built to plans light RV4 with an 0-320 has extremely well balanced controls in all three axis making her a delight to engage in? ACM? dog fighting with a pitch change ability that?ll make ?Forty Second Boyd? proud.

As I mentioned to prospective buyers some 28 years ago when I was still giving rides, Van?s RV4 built to specs, is the most fun you can have with your clothes on. For us, this little plane has performed well beyond expectations and perhaps that?s why she?s still in our hangar and flying often.
Check out ?cumulusgrandus? on You Tube for proof of the pudding.

Cheers, Hans

Thank you Hans for your inputs

E2A

Hi

I rebuilt an E2A for my 4 with 8.5 to 1 pistons and my aircraft out performs every other light single at the airfield. It has a Sensenich FP metal prop and is a super performer. I did see increased power when I fitted two p Mags. The Sensenich FP prop is heavy and I will change this to a Whirlwind GA or Catto. That's if dont decide to go CS.

I have an 0-360 in bits so almost the opposite sotuation to you. I could rebuild that and put it in my 4 but am conscious of th the weight up front. The thing to do is keep the aeroplane light. With an E2a amdVs it will perform really well if you keep the weight down.

Why not look into converting your existing engine into an (I)O-340?
That will get you to almost 180 HP without adding any weight.

Or check with Dayton Murdock. His O-320 has high compression pistons and a helicopter cam for a "little" extra power.

Heck, send your cylinders to Ly-Con and have them ported while you are at it, that will get you some extra power as well.

If you decide to go with a CS prop, don't forget to modify your firewall to make room for the governor. Vans has a kit for this - made out of stainless steel of course.

I was very happy with my 180 hp O-360 RV-4 with a FP prop. Kept it simple and light. Never considered nor needed a CS.

I would argue my IO-360 with the whirlwind 150 prop is the same, if not lighter than an O-320 with a metal prop. I get the added benefit of 200 hp (higher compression piston, flow matched heads, balanced components) and constant speed prop. My empty weight cg is within a 1/4" of what vans recommended.