H2AD Change Out to D2G

[339A]

I broke down and placed an order for a new XO 0320 D2G engine from Vans. Just noticed that it has a scheduled ship date of 1/14/27. So, this has me thinking ahead...

Dimensionally the H is the same as the D, the Carb, FAB, prop bolts, hub, engine mounts, exhaust all the same. After that I'll need to change a few things.

How many things can I pre-order to save some money and time?

The fuel and oil lines will be 24 years old, it's time to replace. I made the ones on it now, but will go with new ones from TS Flightlines. Do they have a shelf life? Considering this will be a straight up swap to the Vans standard 0320 configuration can they be pre-ordered? The only question would be the location of the fuel flow & oil transducers.

Engine mount isolators, stupid expensive for a piece of hard rubber... do they have a shelf life? Who has the best price?

I will need to order some baffle parts as the H accessory case is different. The front and rear baffles I had to modify, I think the rest should be OK.

The bottom cowl should remain unchanged. The top one can lose the distinctive H2AD bumps and I'll need to put the original oil door where it belongs.

I plan to do the Taper pin mod on the nose strut while it's off. Looking for anyone willing to loan me a reamer?

I'm sticking with magnetos, no real change for me. I just loose the Dual Bendix mag.

This is just a start, but looking for input on what I might be missing or should update...

I have no complaints about my H2AD, it has been a good reliable engine. It had 780 hours on it when I bought it. It was a factory Lycoming overhaul. Has always burned 1 quart every 10 hours. Oil analysis comes back with no problems. By the time I remove it, total engine time will be around 3100 hours. So, if anyone is looking for a running H2AD, this one will be for sale.

Thanks,

 

[planenutz]

I'm looking at pulling out an H2AD in the next couple of months for a friend of mine. The engine has been running on condition for years and has been going well, however it's definitely getting tired. When the engine was installed on the RV-6, the cylinders had been given a bit of a clean-up but the bottom end was original and had done about 1800 hours since overhaul. It's now done an additional 1,100 hours in that airframe and it's been flawless. We run it on 15W50, preheat it in winter and it never leaves the chocks until the oil temp is in the green.

We looked at the option of replacing it with something different but the number of changes we would have to make wasn't encouraging, so in the end we found another H2AD and this one is a month away from leaving the overhaul shop.

Besides the baffles - which are completely different (and therefore quite a big job) - the fuel lines will definitely need to be replaced as the Fuel Pump is in a different location. It's a good opportunity to replace all the hoses though, as you say. The engine mount will be ok but you no longer need that big hoop at the top. Your oil dipstick hatch will need to be relocated on your top cowling as the H2AD dipstick is on the top while the other engines are off to the side. You'll be glad to get rid of the Dual Mag... but it's a great opportunity to go electronic ignition and I would encourage you to do this if you can. You'll need to get rid of your stock of oil filters because the new engine will use a different part number. Your Oil Breather Tube will need to be replaced too as the H2AD is in a slightly different configuration.

Hope that gives you something to think about. Nothing is impossible of course... it just all takes time and effort.

 

[Dugaru]

I have no complaints about my H2AD, it has been a good reliable engine.

We are putting an H2AD on our Zenith 801 Project. Definitely has a few quirks (dimensionally, and we’re ditching the dual mags in favor of EI), but in general I think they are underrated. For the ones that are still in the field, the original problems seem to have been ironed out long ago.

 

[blaplante]

Also, it is *possible* to make up a Bendix mag that will drop in as a single mag into the dual mag hole... gives the option of one EI, one Mag. For those thinking about using an H2AD.

 

[339A]

I'm looking at pulling out an H2AD in the next couple of months for a friend of mine. The engine has been running on condition for years and has been going well, however it's definitely getting tired. When the engine was installed on the RV-6, the cylinders had been given a bit of a clean-up but the bottom end was original and had done about 1800 hours since overhaul. It's now done an additional 1,100 hours in that airframe and it's been flawless. We run it on 15W50, preheat it in winter and it never leaves the chocks until the oil temp is in the green.

Given the lead time from Vans and the fact that the H is at 2950 hours, it's time. It has been a solid engine. If the new engine ships in January of 2027 it will be an 18 month lead time. I hadn't thought about the oil breather tube, plus the fuel pump overflow will be different.

Mike, I noticed we both joined this forum on the same day, January 18th 2005! More than 20 years ago.

 

[rbibb]

IIRC there are some differences in the engine mount geometry. A “standard” mount for a “regular: O320 won’t work for an H2D is what I remember. That said, a mount for an H2D may work for an otherwise standard O320. The difference had to with accommodating the dual mag setup. I was considering an H2D when I built my -4 35 years ago and at that time no off the shelf mount was available for it is my recollection.

Just make sure so you don’t have any surprises when it comes time to hang the new engine on your bird.

 

[planenutz]

Given the lead time from Vans and the fact that the H is at 2950 hours, it's time. It has been a solid engine.

Mike, I noticed we both joined this forum on the same day, January 18th 2005! More than 20 years ago.

2950 hours is a pretty good run, yeah. Great effort! Our experience is similar here. As Dugaru mentions above they're a little underrated due to their early history but if you look after them they seem to go well and they were always slated as being a true 160 HP engine, unlike some other variants. I definately dislike the dual magneto, but only because its expensive to maintain and a pain to remove and install in these airframes.

Yes, more than 20 years ago... I'm pleased we're still here. We were some of the very early settlers.

@rbibb - You're correct. When installing the H2AD, the engine mount requires a modification to the top tube which runs between the top engine mounts. You need to cut out the original tube and weld in a replacement with a more significant bow to it. This big bow clears the rear of the engine, which is a bit taller than other variants. When fitting other engine types its not necessary to go back to the original bow as there's no interference. The mount change has nothing to do with the magneto, but you're right in saying that getting the mag installed is a horrible job as its very tight back there.

 

[fixnflyguy]

I have been running and H2AD in my RV-4 for 15 years. I'm also a long time APIA, and fully understand all the differences. Its a solid 160HP engine that will last as long as all the others, and many still live in C172's. VANs once sold a special mount for the H2AD (at least in the -4) that has a "bowed" upper crossbrace to clear the accessory case. The later Dynofocal 1's incorporated that into all the mounts because it didn't affect the other O320's. These engines are often bargain deals from C172 180HP upgrades. I machined off the mechanical fuel pump boss and governor boss corners to keep from cowl bumps, and run an electric pump, with the electric boost pump back-up. I still have the dual mag set-up, which is also used on many other Lyco's and is another mis-understood feature. Yes, the baffles and dipstick location are different, but since I built mine, those weren't something I had to change later. All the Vetterman exhaust, FAB and various bits were same as other O-320's. Here is my -4 install...I have zero regrets with this engine.

 

[Dugaru]

IIRC there are some differences in the engine mount geometry. A “standard” mount for a “regular: O320 won’t work for an H2D is what I remember.

Correct, and you are right that the “hump” at the back gets in the way. We had to modify our standard mount, which otherwise fit. Vans used to sell a mount that would fit the H2AD, not sure if it still does.

 

[Dugaru]

These engines are often bargain deals from C172 180HP upgrades.

That’s exactly how we got ours, it came off a flying 172 that was being upgraded to 180. Scored the prop as well! Price was great, as the market still seems to undervalue these based on ancient history, apparently. We couldn’t be happier with the deal.

 

[339A]

That’s exactly how we got ours, it came off a flying 172 that was being upgraded to 180. Scored the prop as well! Price was great, as the market still seems to undervalue these based. We couldn’t be happier with the deal.

I have been running and H2AD in my RV-4 for 15 years. I'm also a long time APIA, and fully understand all the differences. Its a solid 160HP engine that will last as long as all the others, and many still live in C172's. VANs once sold a special mount for the H2AD (at least in the -4) that has a "bowed" upper crossbrace to clear the accessory case. The later Dynofocal 1's incorporated that into all the mounts because it didn't affect the other O320's. These engines are often bargain deals from C172 180HP upgrades. I machined off the mechanical fuel pump boss and governor boss corners to keep from cowl bumps, and run an electric pump, with the electric boost pump back-up. I still have the dual mag set-up, which is also used on many other Lyco's and is another mis-understood feature. Yes, the baffles and dipstick location are different, but since I built mine, those weren't something I had to change later. All the Vetterman exhaust, FAB and various bits were same as other O-320's. Here is my -4 install...I have zero regrets with this engine.

DITTO... that is exactly how I got mine. It was a 172 upgrade to 0360. I already had the Dyna 1 mount and was going to swap it out with H2AD mount. When I called Vans they said, "We can send you the curved tube to weld in place" it was way less money than shipping mounts back and forth. So, that's what I did. BTW nice job on the install.

2950 hours is a pretty good run, yeah. Great effort! Our experience is similar here. As Dugaru mentions above they're a little underrated due to their early history but if you look after them they seem to go well and they were always slated as being a true 160 HP engine, unlike some other variants. I definately dislike the dual magneto, but only because its expensive to maintain and a pain to remove and install in these airframes.

This is one of my concerns, is the D2G a true 160 HP? My 9A at 8,000 feet, 2,400 RPM with the CATTO prop indicates 145 TAS. If I max it out, roughly 2,600 RPM I'm at 160 TAS. I'm curious if the Torque curves are different between the H and the D... are those available from Lycoming somewhere? I'm worried I'll see a TAS drop at the same RPM's. Not much I can do about it though...

 

[Dugaru]

When I called Vans they said, "We can send you the curved tube to weld in place" it was way less money than shipping mounts back and forth.

Good plan. We cut the existing curved tube and had it welded a little further back. Seems like the perfect solution.