[N941WR]

Posting for a friend -

My friend, Tom, has an RV-4 with an O-320 ?H? engine that just gave him its final and most memorable flight.

Tom, would like to replace the ?H? with a non-H 160 hp O-320. He plans to stay with the fixed pitch prop, so no change there.

Here are a few questions:
1. Which mount does the ?H? engine take? I believe it is a Dynafocal 1 mount.
2. What dash number should he look for to minimize issues with the installation of the new engine? ie., is there a forward or rear sump that he should avoid? Same prop bolts as the ?H?? etc.
3. Is the exhaust manifold interchangeable between the two engines?
4. Other than moving the fuel line from the front of the engine to the rear, what other changes can he expect?
5. Are the baffles interchangeable or will he need to replace them?
6. Once he has the engine removed, what areas should he inspect closely? The weld clusters at the bottom of the engine mount, the inside of the firewall, what else?
7. Will he be able to use his existing carb?

Any other comments, thoughts, suggestions, etc. would be greatly appreciated.

He has already decided that he does not want another ?H? engine and does not wish to rebuild the one he has, so please don?t suggest he keep it. Also, if any of you want an ?H? core, let me know and I?ll pass along your request to Tom.

 

[JoeBlank]

Bill,

First off, glad the last flight for the engine ended well. Second, have him call Vans and we can cross reference some of this info for a better answer...

1. The 'H' version uses it's own unique mount. So I think he'll need a new mount. May be a good opportunity to switch to the 'Tall Gear' if he hasn't yet.
2. Best (I)O-320 version would be the -D1A. Eliminates all of the known issues. This would need a Dyna-1 mount. Other models will work though.
3. The crossover exhaust will probably work OK but I'm not absolutley sure. Was he using a 4 pipe or a crossover or...?
4&5. Possibly, the baffles might be different due to the engine case. Also the fuel pump will be at the left/rear of the engine. I think the mag drive might be different too...
6. Everything!
7. High probabilityof yes...

 

[Andrew M]

Go to TSDS E-274

I just looked at the Type Certificate Data Sheet under note 5, that is probably the best place to start. It list the model differences. The IPC might be able to help to. This is something that the best advise I can offer is how to figure it out for yourself. http://rgl.faa.gov/Regulatory_and_G...6235A06FF153FFF28625760E0051F018?OpenDocument

 

[fixnflyguy]

"H" replacement

Bill,
I have a -4 with an O320H2AD, and it is working very well for me..there are some teething issues not everyone understands. The mount, I am fairly certain, will work with all the other dynafocal 1 engines. It just has a unique upper crossmember that accomodates the accessory case. Since I dont know the nature of the final flight with his H engine, I am curious as to what happened, as we all learn from these issues. I am also interested in what is left of the engine, as I would like to build a spare for when mine is ready for overhaul. I built my engine from a run-out and know the engine well, and also built my baffles, wich are definately unique to the H model. Please PM me if you want do go deeper into details, as I am only a 20 minute flight away.

 

[Russ McCutcheon]

The H mount is Dyna 1 already and I am almost positive it will fit the standard engine, the only difference is the top curved tube on the dynafocal ring, if for any reason that tube is in the way and he wants, I can change it to a standard Dyna 1 mount.

Yes check for cracks on the mount around the area of the bottom corner feet, the feet tubes themselves just above (1/4” to ½”) the washer, the weld just above the washer and the gear socket tube, also look for deformation of the center attach tube between the center feet and the socket tubes.

Questions or concerns about the mount, feel free to give me a call, send photos, and or send me the mount for modification or repair.

 

[hudgin]

There are a couple of businesses that switch out the H 2AD in the 172N and put an E2D or E3D or a O-360A4M in its place. I think one is Just Plains and the other is Penn Yanns Aero. I don't think much modification is done except for the O-360 mod. But the point is I am sure they could help you.

 

[rvsxer]

The H mount is Dyna 1 already and I am almost positive it will fit the standard engine, the only difference is the top curved tube on the dynafocal ring, if for any reason that tube is in the way and he wants, I can change it to a standard Dyna 1 mount

True. I received my O-360 mount and had it painted (before they were powder-coated). I then realized the top tube was different. Van's said it was an O-320 "H" mount and it would work. So did Lycoming. It has not presented any problem except for the vacuum pump mounting (it had to be rotated 90 degrees for the plumbing to clear), usually not a consideration now. Anything else on that drive pad would be okay.