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IO540 for a 7A

E

elfiero

Member
I am getting serious about buying a 7A and was wondering if there is any info out there about using a 540 Lyc? I really want a 7A not an 8, so I don't know if any of the harmon info is any good to me. I also would consider a Continental 520 if I could find a mount and a cowl. Any suggestions you guys might have would be very helpful!
Bruce
 
elfiero said:
I am getting serious about buying a 7A and was wondering if there is any info out there about using a 540 Lyc? I really want a 7A not an 8, so I don't know if any of the harmon info is any good to me. I also would consider a Continental 520 if I could find a mount and a cowl. Any suggestions you guys might have would be very helpful!
Bruce
Click to expand...

The parrallel valve 540 is possible, but I doubt you could get the Angle valve to fit. I there any reason you need the extra 50 HP from a 540 (260HP max) that it'd be worth the trouble over a IO-390 at 210+HP?
 
Yeah, there is a reason. I can get a low time IO540 for 3500.00, or I can get a mid time IO520C for 2500.00. With either of these, I could loaf them along at low RPM and MP and still get blazing speed. I don't think any of the above is possible with a IO390.
Bruce
 
I just skimmed over that guys site. He reports 24 gal/hr fuel burn. Yikes! I'd rather install an Innodyn Turbine if that was the case.
 
Nope, I have friends in the engine O/H bis and I'm a part time A&P who works for them once in a while....
P.S. all the kit builders have driven the price of O-360s clean outta site.
 
I know folks are bolting these up to their -8 and -7 in greater numbers. We have probably the largest concentrations of these in Indy with the twin dragon airplanes and several others. The only thing I'll say is that the airframe was not designed for these engines and the margin for error is relatively slim if you get the nose pointed downhill. The real problem with these conversions is that you will be over Vne faster than you think. I'm ignoring all the engineering parts of this puzzle since I'm guessing you already know that you'll need different mounts, cowls, etc. and should beef up the empennage, skins, etc. Since I've built an RV and a Rocket, I have firsthand experience with the differences in the two designs which are very similiar in appearance, but are much different under the skin for the most part, just to hang a larger engine out front.

I'm not trying to rain on your parade or anything. They will fit and folks have done it and it will fly, no question. I've heard secondhand that several of the folks who have done so have said privately that they wouldn't do it again. I don't know it's true or not
 
540 in a -7

Bruce-
You should definitely get in touch with Scott. Putting the 540 in a -7 creates many problems, not the least of which is W&B issues. Scott's plane weighed in at about 1355# or so without paint. Even with two standard batteries located halfway down the fuse, he was still barely in the CG envelope. If you tried to do this on a -7A, getting the plane in CG may be a real problem.
For the trouble you go thru, I would really look at this option closely. It may end up costing you more in the end than spending more on a good 0-360 up front!
Good luck whichever way you go!
Bill Waters
 
RV_7A said:
I just skimmed over that guys site. He reports 24 gal/hr fuel burn. Yikes! I'd rather install an Innodyn Turbine if that was the case.
Click to expand...
He's probably running at WOT to break in the engine. It will burn a lot of fuel down low at WOT, but after that, fuel flows around 10.5 are very easy to get. That's still higher than the fuel flows for an IO-360 but you do get some extra speed to offset the higher flow.
 
noseheavy?

So I can believe that an IO-540 would push the CG envelope of the -7 too far forward. But I have a hard time believing that even the heaviest 360/prop combo would cause you a problem. After going through Dan C's w&b page, it shows that almost everybody has too aft of CGs when the 7 is fully loaded. I couldn't find a single one that had any forward CG concerns no matter what the loading was. So I would think that a heavy engine/prop would be a relatively good thing for a -7 (or especially -7A since they tend to be even more aft from the mains, I suppose). Sure, it adds to your total weight, but at least you can load it up all the way without any CG problems like you'd have in lighter ones.
 
Too Heavy

If Scott's airplane really came in at 1355 lbs., that tells the whole story right there. My Rocket, in the same configuration without paint, weights 1242 lbs. and it was not built to be a light weight airplane. I have full leather, walnut trim, and a lot of electrical systems.

Given that the -7 weights 100 lbs more and the gross weight is 200 lbs less than a Rocket, I don't see why you'd want to go through the trouble and engineering to put a 540 on one, even if it was free! You'd just end up with a -7 without much utility and (IMHO) one that would be dangerous to fly downhill.
 
If it felt heavy ALL the time...

I can tell you (fwiw) that when you load the plane to mfr's gross (1800lbs in my RV-7), it is just not as pleasant to fly. My RV-7 weighs 1113 and has a max gross of 1950.

When Jen and I travel, full of bags & crap, when we get home I love to ditch all the bags, empty the plane out, and then go fly. It's like night and day. Even at 1500 pounds or 1600 pounds, it feels remarkably lighter, more responsive (on the ground and in the air). The thing just leaps right off the runway. It's sheer joy.

Above 1750 lbs or so, the thing is a slug on the ground -- you can really feel how heavy the tailwheel is weighted, how much more power you need just to get rolling, etc. Once in the air some of that heaviness goes away, but it's still way less responsive.

If my plane felt that heavy ALL the time, I wouldn't be as happy with it. And this is coming from a "power hungry" pilot like me.

I am seriously skeptical about the 540 producing any significant difference in performance over a well-tuned well-running 200+hp 360 variant. And I'm talking about an RV proper here, not a chopped-wing Rocket variant -- we all know the performance is amazing on the Rocket. But on the RVs, is the performance all that stellar? I doubt it. Show me the numbers!

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
Super -7 weight

Sorry guys, the Super -7 didn't weigh 1355# as previously stated, it only weighed 1349#. Empty CG was 78.23". For those who might be considering this confiquration, and are interested in seeing the results of this mod, Kahana has W&B information on the Super-7 and -8 posted on his website, www.mstewart.com, go to the Super-8 page. His spread sheet is really nice!
Bill Waters
 
Really!

elfiero said:
Nope, I have friends in the engine O/H bis and I'm a part time A&P who works for them once in a while....
P.S. all the kit builders have driven the price of O-360s clean outta site.
Click to expand...
I'll give you or your friend $3,500 for a low time IO540 (parallel valves). This sounds unbelievable, since a run out core sells for more. Heck I'll go $7,000. I mean if your buddy is going to be your Santa Clause and make you a gift, that is great, but it is not the case for 99.999999999% of the rest of us.

The Harmon Rocket, F-1 (Team Rocket) and the RV-10. They all use (I)O-540's. The market is also dried up on 540's. I am sure your friend knows he can sell his "LOW TIME" ;) engines for way way way more than $3,500.00 (by at least a factor of 6), but I will buy 3 of his low time 540's for $3,500.

An overhauled/new aero sport (I)O-540 sells for about $37,000, and you can get a low time IO-540 for $3,500? The crank cost more than that.

The story of cheap 540's may have been true 15 years ago, but not any more. Congratulations on having a generous friend. Using a 6-banger in a RV-7 is not going to save most average builders money.

Cheers George
 
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Some detail on the Super 7

I know this plane well and have flown it. Fuel flow is just like any other 540. His 24gph is wide open. His plane is a tank cause he intentionally built it that way due to his background. Mechanic for the heavies. Getting the CG in range is simply a factor of battery placement. He could have saved weight in many areas and chose not to. He used structural adhesive on EVERY joint, duplicated the electrical system from a Cirrus, and way over built the thing cause that is all he knows how to do from his day job.

There was no problem getting the engine in the cowl. The mods he made were exactly like mine on the S8 which you can get from my web site. All caveats including Randy's apply. His is the first Super 7 that Im aware of.

best
Kahuna
S8 flying for a week. Yipee :D
 
Super RV-6?

Kahuna said:
His is the first Super 7 that Im aware of. Kahuna S8 flying for a week. Yipee :D
Click to expand...
There was a super RV-6 built a few years ago. He stretched the fuselage and I think clipped the wing. He is a building contractor and lives in the SFO area. I met him at Oshkosh and he flew in with his super RV-6. This was a number of years ago (at least 5-6). He was thinking of making a kit of it like Harmon who I think gave him some advice on the project. Anyone know who I am talking about? G
 
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Super 6

Boyd C. Braem is the guy who built the Super 6. A quick search on the Matronics list for this info. I once considered building one, but the M1 Speedcruiser that International-HPA (http://www.international-hpa.com/proj_speedcruiser.html) has on there site caught my eye. Don't believe it has ever materialized as a kit though. Too bad, would have probably been a nice kit for those wanting a two place side by side -540 powered bird. Anybody else know anything about it?
BB
 
Why do it.

f1rocket said:
I don't see why you'd want to go through the trouble and engineering to put a 540 on one, even if it was free! downhill.
Click to expand...

Matched hole, Side by side, insurance.
Kahuna
 
Dans skeptical

dan said:
I am seriously skeptical about the 540 producing any significant difference in performance over a well-tuned well-running 200+hp 360 variant. And I'm talking about an RV proper here, not a chopped-wing Rocket variant -- we all know the performance is amazing on the Rocket. But on the RVs, is the performance all that stellar? I doubt it. Show me the numbers!

)_( Dan
RV-7 N714D
http://www.rvproject.com
Click to expand...

Well well Sharpie, perhaps a time to climb off my wing and a speed run with you would do the trick. Posted numbers falls into the talk is cheap category. and then there is the real test.... What do you say there... You up for it?

And whats this well tuned well running stuff. You want me to shut off 2 cylinders or sompthin? You think a well tuned 4cyl against a poorly running 6 is a test? Cummon now. And what is Significant? Would 20 knots fall into that caegory? how about 800fpm? In dunno but sure seems like it to me. There is just no substitute for cubic inches.
Kahuna :p
 
Kahuna said:
Matched hole, Side by side, insurance.
Kahuna
Click to expand...
It won't take long for the insurance guys to catch on. I think these RV-variants will suffer the same as the Harmons, which is why the Rocket suffers high insurance premiums. The airframe is not designed for the engine and as a result, is too light on the tailwheel. This leads to all kinds of handling problems. What was your tailwheel weight and how does that compare to typical -8s?
 
Jeez, what did I start here? I'm sorry, I won't do it again. BTW, the prices I quoted are for me only, they will not sell engines to anyone else that cheep. On the other hand, a few months ago, a '63 aztruck with the O540 engines sold for $4500.00 on ebay- yank the engines and sell the rest for pop cans and you can just about recover 1/4 to 1/3 of your "investment". then sell the second engine and viola- you have a "free" engine core plus some money to sink into your engine. I didn't jump on it 'cause I have not yet decided what or if I'm going to build.
 
Don't Take it Personally

You really asked a very good question and I think the discussion is a good one. Controversial threads (like this one) tend to get hijacked a little bit, but for usually good reasons.

Thanks for asking the question and good luck to you on your future building decision. If you can get a cheap 540, you might give a -10 or a Rocket a look. Take care.
 
Kahuna said:
Well well Sharpie, perhaps a time to climb off my wing and a speed run with you would do the trick. Posted numbers falls into the talk is cheap category. and then there is the real test.... What do you say there... You up for it?

And whats this well tuned well running stuff. You want me to shut off 2 cylinders or sompthin? You think a well tuned 4cyl against a poorly running 6 is a test? Cummon now. And what is Significant? Would 20 knots fall into that caegory? how about 800fpm? In dunno but sure seems like it to me. There is just no substitute for cubic inches.
Kahuna :p
Click to expand...

Jeez, didn't mean to offend you man. I guess I'm just interested in seeing your performance data once you get it all faired up (if not already) and do some speed runs. I'm a little skeptical about how fast the top end will be, and how much faster it'll climb since it's considerably heavier. You gotta pardon my skepticism, and I assume I'll be surprised when you publish the performance data.

By "well tuned" I just mean the thing is broken in, timed right, breathing well, and happy.

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
Skeptical?

dan said:
Jeez, didn't mean to offend you man.
)_( Dan
RV-7 N714D
http://www.rvproject.com
Click to expand...

Absolutely none taken friend. Just messin with ya:)

I expect to get her faired up this weekend if I can get the oil leaks under control and start some real flight testing. Got my data cards ready. So far I have only taken off, run WOT, couple stalls, landed, fixed major sqawks, and do it over.


Kahuna
 
the Rocket builders go thru this decision making all the time.

260hp or 300hp? Only difference is in the climb (straight up) and then when level everything feels and looks the same anyway.

"Dad, you definitely want the 300hp or 330?" :cool:
 
f1rocket said:
It won't take long for the insurance guys to catch on. I think these RV-variants will suffer the same as the Harmons, which is why the Rocket suffers high insurance premiums. The airframe is not designed for the engine and as a result, is too light on the tailwheel. This leads to all kinds of handling problems. What was your tailwheel weight and how does that compare to typical -8s?
Click to expand...


None of this prediction over 3 years ago happened Randy. More are flying, none are dying. My insurance is dropping annually and has always been matched with 4 banger prices. Its the airframe to them.
Best,
 
You may not be seeing it but the Rocket guys are. I hope they don't catch on so enjoy your insurance premiums. I truly hope they last for you.

BTW, what are you doing poking around in three-year old posts? Slow day at work?:D
 
Engineering considerations on the "Super" RV's ...

Going to a 6-cyl on an RV will change structural and aerodynamic characteristics. I'm only illuminating these items for those who care:

Aerodynamic:
  • In a tractor configuration, the propeller has a destabilizing effect in pitch and yaw. Locating the prop further forward and/or increasing its thrust will reduce stability. The added side area of the longer nose adds to this effect. To retain the original aircraft's static stability margin, the horizontal and vertical tail surfaces would have to be enlarged or moved back. This may not matter to a pilot who doesn't care to retain the original neutral point/stab margins.
  • If the cg is allowed to drift forward enough, the aircraft may not remain fully controllable in pitch at very low speeds (ie not able to three point in the flare - depends how far fwd the cg goes but this condition is attainable with a heavy engine/prop).

Structural:
  • It goes without saying the heavier engine will require a new, stronger engine mount if the original g-limits are to be retained.
  • Mounting a heavier engine drives larger loads into the fuselage attach points and related structure. Unless this structure is modified to accomodate the higher loads implied, the original g-limits on the aircraft would have to be reduced to prevent overloading the engine attach structure (within the fuselage). Keep in mind the larger heavier prop drives gyroscopic loads higher too.
  • It also stresses the fuselage in bending more during accelerated flight (+/- g's).
  • Concentrating a higher percentage of the aircraft's empty weight in the fuselage (vs the wings) will produce greater bending and shear loads in the wing spar and fuselage wing box.

PLEASE NOTE I'm not saying "don't do this" nor am I taking shots at anybody here. I'm only providing this information to help those of you with "super" RV's be more aware of those areas affected by such changes.

And, YES, there is no substitute for cubic inches. Any fighter pilot can tell you of times where he ran out of thrust no matter the airplane...
 
Barnes' Stormer

I built an rv6 with an IO540, absolutely love it. Have over 450 hrs on it. The fuselage is 10" longer, almost all the skins on the fus. are heavier, the wings are beefed up, the tanks are bigger, has an rv8 tail, heavier brakes, and a few other mods. I don't think it would be wise to put a 540 on a 7 as kind of an after thought. If some one wants to build an old style 6 as a 540 powered plane, I have the drawings and an engine mount for sale as well as tech assist.

Steve Barnes [email protected] (707) 972 3582
 
After flying some 8000 hours in airplanes modified to do a job they were never designed to do I can tell you that if you want an IO-540 build an airframe that was designed for it. You will be much happier. And in the end the price will be the same.
 
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