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RV-6 engine replacement

newt

Well Known Member
My RV-6 is on about 1830 hours. I'll have an annual condition inspection in October, then I think there'll be engine work in 2021.

Current engine is a carburetted O-320-D2A with a Sensenich fixed-pitch cruise prop.

I didn't build the aircraft.

The current fuel system has plumbing feeding an Andair valve supplying the suction side of a Facet fuel pump on the inside wall of the fuselage between the pilot seat and the rudder pedals, with the pump discharge feeding a gascolator on the engine side of the firewall, which in turn runs to the engine-driven fuel pump.

It's still more than a year and a half away, but planning is good, and the direction I'm tending towards now is to take the O-320-D2A off and replace it with some variant of an IO-360, probably also with a fixed-pitch prop.

The change from carburettor to fuel injection is going to involve fuel system modifications: I'm anticipating that the Facet pump will end up in the trash, with a new high pressure fuel pump and new plumbing.

I'm sure someone has gone down the path of carb to fuel injection before, and if anyone has advice I'd love to hear about it.

Are folks generally keeping high-pressure fuel out of the cockpit, so where's the right spot for the electric pump? Is the gascolator necessary? Considerations for routing fuel lines to avoid vapor lock? How are fuel systems handled in modern certified aircraft? Anything else I'm not thinking of?

Thanks,

- mark
 
If it has good compression, doesn't use oil, and isn't making metal......fly it!

....unless you just want a new engine...... :)
 
My RV-6 is on about 1830 hours. I'll have an annual condition inspection in October, then I think there'll be engine work in 2021.

Current engine is a carburetted O-320-D2A with a Sensenich fixed-pitch cruise prop.

I didn't build the aircraft.

The current fuel system has plumbing feeding an Andair valve supplying the suction side of a Facet fuel pump on the inside wall of the fuselage between the pilot seat and the rudder pedals, with the pump discharge feeding a gascolator on the engine side of the firewall, which in turn runs to the engine-driven fuel pump.
That is the "standard" fuel system for a carburetor, with the exception of the Andair valve, the builder opted to replace the standard valve with the Andair same location, same function.

...

The change from carburettor to fuel injection is going to involve fuel system modifications: I'm anticipating that the Facet pump will end up in the trash, with a new high pressure fuel pump and new plumbing.

I'm sure someone has gone down the path of carb to fuel injection before, and if anyone has advice I'd love to hear about it.

Are folks generally keeping high-pressure fuel out of the cockpit, so where's the right spot for the electric pump? Is the gascolator necessary? Considerations for routing fuel lines to avoid vapor lock? How are fuel systems handled in modern certified aircraft? Anything else I'm not thinking of?

Thanks,

- mark
The "standard" FI setup is to put the high pressure backup pump just forward of the Andair fuel valve.

The gascolator comes out and can be replaced with a bulkhead fitting to fill the hole.

Somewhere in that mess, you might want to think about installing a fuel flow meter (the type depends on your engine monitoring system).

Contact Van's and ask them for the drawings for the fuel injected setup, they are pretty generic.

What I don't know is if you will need a shorter engine mount when you switch to the IO-360 parallel valve engine from your O-320.

Good luck!
 
If it has good compression, doesn't use oil, and isn't making metal......fly it!

That's certainly a consideration. But it butts up against the extremely annoying way that I get left behind on the outside of echelon turns with RV-7s :) An IO-360 is less than 7 kg heavier than an O-320. Hardly any weight for quite a bit of extra power margin.

Besides: It's 2020, and we worked out how to eliminate carb ice risk half a century ago. It's borderline embarrassing to still have to deal with it.

- mark
 
What I don't know is if you will need a shorter engine mount when you switch to the IO-360 parallel valve engine from your O-320.

That is a fascinating consideration, and I'm glad I asked here.

Thank you!

- mark
 
re carb icing, never had any icing with my O-360 despite extensive use in conditions prone to produce. But never say never...

On the other hand the main advantage of switching to a fuel injection would be fuel economy since a more effective LOP can be done. Inlet icing is still very possible and probable in given conditions, so an alternate air is a must.
 
Besides: It's 2020, and we worked out how to eliminate carb ice risk half a century ago. It's borderline embarrassing to still have to deal with it.

- mark

Just as a datapoint.....I've been flying my RV-6 (O-320, carb) since 1999 and have had two minor carb ice incidents, both during mile-long taxi with a cold engine after the first start of the day. Even though we see very humid conditions in Alabama I have never experienced in-flight carb ice with the O-320.

Now the O-200 in the biplane is another matter...that thing can make ice in a heartbeat! :)
 
I switched from an O-320 to an O-360 during my build on a RV-6A and used the same motor mount.

Gil, can you tell me ?approximately? how much further the 320 mount pushes the engine out as compared to the 360 mount? I?m thinking about using the 320 mount on my Catto prop equipped PV 360 -7 build to help with W&B.
 
Gil, can you tell me ?approximately? how much further the 320 mount pushes the engine out as compared to the 360 mount? I?m thinking about using the 320 mount on my Catto prop equipped PV 360 -7 build to help with W&B.

I believe that is a -7 issue only....
 
Mount should be the same. Baffling will likely have to change. Recollection is that the 320 and 360 parallel valve are the same length. But the width is greater on the 360.
 
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.......... the extremely annoying way that I get left behind on the outside of echelon turns with RV-7s :) An IO-360 is less than 7 kg heavier than an O-320. Hardly any weight for quite a bit of extra power margin.

- mark

The best upgrade for formation flying is a Constant Speed Prop. A friend just put a C/S Hartzell on his O-320, and he is amazed at the difference in formation flying.

So, even if you go with an IO-360, consider a C/S prop.
 
I believe that is a -7 issue only....

Yes, I think you?re correct....and that?s what I?m building and that?s why I?m thinking about going with the 320 mount to hang my 360 on. If it pushes the engine forward an inch or two I believe it would really help with the W&B issue. Do you happen to know how much further forward it pushes the engine?
 
Mount should be the same. Baffling will likely have to change. Recollection is that the 320 and 360 parallel valve are the same length. But the width is greater on the 360.

Correct....due to the longer stroke.... the the crankshaft length is the same.
 
Inlet icing is still very possible and probable in given conditions, so an alternate air is a must.

Vans own alternate air system doesn?t pull warm air. They just pull alternate air.
The only inlet ?icing? that might be mitigated would be flying in a snow storm, and then it?s the filter clogging, not the inlet icing.

Willing to learn here, but in all of the alternate air discussions here on VAF, this has never come up to my knowledge.
 
The best upgrade for formation flying is a Constant Speed Prop. A friend just put a C/S Hartzell on his O-320, and he is amazed at the difference in formation flying.

So, even if you go with an IO-360, consider a C/S prop.

Allows you to power manage sooo much better some say it?s cheating!
I flew with many O320 fixed pitch guys in formation and the only time the experienced guys had an issue was when one of us CS guys got behind and cheated or lead didn?t hold standard ;)

Throw the chute out, or throttle forward and watch those hapless fixed pitch guys scramble! Unfair.....
 
By the way, the Bucker?s 0320 made it over 2300 hours. I flew it for ten years after TBO. Per Sam?s point.
 
There are many 320?s in the fleet well beyond tbo. Some have even doubled tbo. Some more than double tbo. That is a hardy engine.
 
Gil, can you tell me “approximately” how much further the 320 mount pushes the engine out as compared to the 360 mount? I’m thinking about using the 320 mount on my Catto prop equipped PV 360 -7 build to help with W&B.

I measured two rv6 yesterday to verify engine mounts and placement. Rv6 with 0360 measures 10.5” from firewall to acc case split line. My rv6 with 0320 measures 11 1/8” from firewall to acc case split line. The 320 mount seems to move the engine 5/8” further forward on my two examples.
 
Allows you to power manage sooo much better some say it?s cheating!
I flew with many O320 fixed pitch guys in formation and the only time the experienced guys had an issue was when one of us CS guys got behind and cheated or lead didn?t hold standard ;)

Throw the chute out, or throttle forward and watch those hapless fixed pitch guys scramble! Unfair.....

One of these days I'm going to hand my RV's keys to one of the CSU owners in my formation group and find out just how good they really are :D

https://www.youtube.com/watch?v=tkUxspoeZzk

- mark
 
I measured two rv6 yesterday to verify engine mounts and placement. Rv6 with 0360 measures 10.5? from firewall to acc case split line. My rv6 with 0320 measures 11 1/8? from firewall to acc case split line. The 320 mount seems to move the engine 5/8? further forward on my two examples.

Perfect....that?s the information I was looking for!! I?ll bet that little bit of difference will make a measurable change in CG and W&B.
 
fuel system changes

By changing from carb to injection, you might have some 'splaining to do with regard to FAR 21.93. My insurance company has made a point of asking every year at renewal time, among other things, whether I've made any fuel system changes. FWIW: I've got 21 years of flying my carb'd 0-320 in Pacific NW weather, had carb ice once on the ground.

Cheers!

- Steven, 1300 RV-3 hours, another one on New Years Day! Aaaand ... its the Dark Ages around here. I think the bad-weather Jet Stream is, like, directly over my home airport :(
 
Jon, we have a newly arrived Bucker at DCU.....cool plane. :)

Beg, borrow, or steal a ride and take the stick. While they aren?t the same airplane two up, close enough. No disrespect to my beloved 6, but the Jungmann still puts that smile and feeling I had in my early years of flying, every time I take it up. Wouldn?t trade my 6 for it though. Lucky to be able to have both.
 
I measured two rv6 yesterday to verify engine mounts and placement. Rv6 with 0360 measures 10.5? from firewall to acc case split line. My rv6 with 0320 measures 11 1/8? from firewall to acc case split line. The 320 mount seems to move the engine 5/8? further forward on my two examples.

I think you must have a later plans version than mine, or they are not RV-6s.

My plans show sheet 50, R-1 dated 9/92 and only one size of engine mount.
 
Another data point on Carb Ice... I've had it on the ground a number of times, and in the air as well. Never to the point where the engine stumbled or quit, but checking carb heat occasionally has cleared "something" that resulted in an RPM increase afterwards.

I suspect that anyone flying with the stock carb heat setup (the tiny tube that crosses the crossover tube) doesn't have enough heat to affect anything anyway, so there may be some carb ice happening that only goes so far and never causes in-flight issues. Certainly, the stock setup isn't enough to even register a change on the RPM gauge on the ground. I switched to a Robbins Wings muff on my crossover pipe when I bought my -6, and now get a definite 50rpm drop when the carb heat is engaged.
 
320 to 360 motor mount

Gil, can you tell me ?approximately? how much further the 320 mount pushes the engine out as compared to the 360 mount? I?m thinking about using the 320 mount on my Catto prop equipped PV 360 -7 build to help with W&B.

The engine motor mounts are the same, there is no additional engine length, only the width of the engine is increased by 1" for the 360 parallel valve engine.
 
Cowl?

Well, personally if it ain't broke dont fix it. The O-320 is one of the most reliable engines in GA. Some double TBO. So unless its eating oil or making metal I would fly it...


But if you want more power that's cool ;)

Is there no problem with the cowl? Horizontal / vertical induction and the -7 has a different cowl for the 320 and 360..?? not the case for the -6?
 
The engine motor mounts are the same, there is no additional engine length, only the width of the engine is increased by 1" for the 360 parallel valve engine.

I know that the length of the 320 and 360 are the same and that due to an increase is stroke the 360 was a little bit wider, but because of the little bit lighter weight of the 320, I thought that the engine mount was a little different.

If the -7 is already a little tail heavy with a 360 and a lightweight F.P. prop, then I?d imagine it?s really tail heavy with the same prop but with a lighter 320, especially if the mount doesn?t push the engine out an inch or two further to compensate for the lighter engine.
 
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