Lycoming O-320 H2AD

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drwet

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Sep 21, 2021
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I fly a Murphy Rebel with an O-320 H2AD engine. The airplane has been in storage for a number of years and I recently resurrected it. I put about 25 hours on it this summer, and while it performed very well, I decided to tear into the engine over the winter, given the stories of camshaft deterioration from prolonged storage in these engines. Sure enough, I have corrosion on the camshaft, and spalling of the lifters. I'm looking at replacing the cam and lifters. It appears I can get a camshaft, but I am having trouble sourcing new lifters for the engine. The only source I can find wants $650 each! Needless to say I am looking for other options.
First, these lifters look for all the world like automotive valve lifters, and I find it hard to believe Lycoming engineered a whole new lifter design in a world filled with hydraulic valve lifters. There has to be an application that uses the same lifter. I have heard that there is a diesel engine possibly from Caterpillar or Cummins that uses the same lifter. Does anyone know of a lifter that will work in these engines?
The other option is to install a cam and mushroom style tappets from another Lycoming engine series. I have heard that this is possible, but that it is necessary to machine the case for the new lifters. Anyone know anything about this?
I am also open to other suggestions.
 

drwet

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So it appears that 'T-mod' is dictated by Lycoming Service Instruction 1406B - now updated to 1406E and essentially involves converting the H2AD engine to mushroom style tappets. If you do that according to the Lycoming Service Instruction, you replace not only the cam and lifters but the case as well. Not really an option. Still looking for a more reasonable solution.
 

TFF

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Not gospel but if I remember the lifters and rockers were 351 Cleveland parts. Which is what broke. I think the cam base cycle was too small. There was a company that made a roller cam replacement at one time. Lycoming will almost not admit that it exists and at one time they would accept one as a core on just about any other engine to get them off the street. If it didn’t have the teething problems, the design would have been more prevalent.
 

Pops

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Not gospel but if I remember the lifters and rockers were 351 Cleveland parts. Which is what broke. I think the cam base cycle was too small. There was a company that made a roller cam replacement at one time. Lycoming will almost not admit that it exists and at one time they would accept one as a core on just about any other engine to get them off the street. If it didn’t have the teething problems, the design would have been more prevalent.
I took a tour of the Lyc factory and part of that tour is visiting the museum. One of every engine that Lyc built was there except for the 320 -H2AD. I ask why wasn't the 320-H2AD included in the museum. The person conducting the tour said " we didn't make that engine", with a smile.
I have somewhere between 1 to 2 thousands hours flying behind one. Never did like that engine.
 

drwet

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Sep 21, 2021
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Thanks for the replies. I have heard the rocker arms are the same as 351 Cleveland parts but this is the first I have heard that the lifters are as well. I have a buddy with a Cleveland in his shop. I'll have to see if I can snatch a lifter out of the engine and take some measurements. As far as the Service Instruction, it is quite clear. Replace the cam, lifters, and case. But I have also heard that the case can be machined instead of being replaced, although I can understand Lycoming not wanting to trust outside shops to modify the H2AD cases.
FWIW we put about 800 hours on our engine over 17 years and the thing was bulletproof. Even with all the spalling and corrosion it runs like a champ. The problem is that it was parked about ten years ago so it's no surprise we have corrosion and lifter spalling. I can't blame the engine. From what I've seen the reputation of the H2AD is overblown. In fact, I like the fact that the lifters can be removed and inspected without splitting the case. As for the dual magneto, we are running a single magneto and an electronic ignition and it works great.
I have also heard that it is possible to have the lifters resurfaced. Ours are not bad so I'm sure they would qualify if I can find a shop that does this. Anyone?
 

Dan Thomas

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I took a tour of the Lyc factory and part of that tour is visiting the museum. One of every engine that Lyc built was there except for the 320 -H2AD. I ask why wasn't the 320-H2AD included in the museum. The person conducting the tour said " we didn't make that engine", with a smile.
I have somewhere between 1 to 2 thousands hours flying behind one. Never did like that engine.
If I recall right, that's the engine that the Bendix dual magneto was developed for. A magneto that has one drive assembly, with an impulse coupling that drives two magnetos in the housing. It sounds real good until you realize that all your power is dependent on that one impulse spring. Those springs have a habit of corroding and breaking, and that knocks the spark on both mags back to TDC or close to it, and the engine makes noise but that's about all it does. You're not going very far.

Continental bought Bendix. They immediately discontinued making those mags and the parts for them, since only Lycomings used it. There are going to be some desperate owners at some point as these things wear beyond repair. There is only one magneto mounting pad on the engine, too, so you can't just install two separate mags.

We had one on an O-540J3C5D (Cessna R182) and it was a real pain to get off and on and to get the internals timed just right. I sure don't miss it. By the time I got it out, inspected and set up wit new points and stuff, and back in again, I was badly scratched up. They bury those things in some installations.

1669346179942.png

By the time the OP gets his H2AD engine fixed up right, including a mag overhaul, me might have spent enough money that he could have traded his H2AD core in for something much more popular and trustworthy and already overhauled..
 

TFF

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If you put in a cam, lifters need to be new or overhauled. Old lifters will ruin a new cam. Being able to pull lifters out is an indication of no mod. I believe at the time the mod was warranty under certain circumstances.

I lived with duel mags on helicopters and built a stand so it wasn’t that hard to time them. While most of my type were shower of Sparks, one nice thing is starting one with an impulse is it’s starting on two mags. The bad thing about one with an impulse is there is so much inertia that it can strip both gears at once. Mag and electronic is pretty nice.

While it’s not a loved child, the bigger issue I see is it’s tall. It won’t fit in a lot of standard cowls of regular cases without changes. Fine if you start with one, but not as easy if you got one for a replacement.
 

Victor Bravo

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Sorry if this is mercenary or inappropriate, but you might find that buying a modestly priced dual-mag O-320 with a prop strike, and putting your H2AD crankshaft in it, is less expensive and less trouble-prone than dealing with the dual mag, the lifters, the cam, doing the T-mod, etc. etc. etc. both short-term and long-term.

What's that, you say??? Where would you find such a prop strike engine at a moderate price???

Funny you should ask, I know of an EAA chapter out West that maaaay have one.
 

speedracer

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Feb 4, 2020
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I fly a Murphy Rebel with an O-320 H2AD engine. The airplane has been in storage for a number of years and I recently resurrected it. I put about 25 hours on it this summer, and while it performed very well, I decided to tear into the engine over the winter, given the stories of camshaft deterioration from prolonged storage in these engines. Sure enough, I have corrosion on the camshaft, and spalling of the lifters. I'm looking at replacing the cam and lifters. It appears I can get a camshaft, but I am having trouble sourcing new lifters for the engine. The only source I can find wants $650 each! Needless to say I am looking for other options.
First, these lifters look for all the world like automotive valve lifters, and I find it hard to believe Lycoming engineered a whole new lifter design in a world filled with hydraulic valve lifters. There has to be an application that uses the same lifter. I have heard that there is a diesel engine possibly from Caterpillar or Cummins that uses the same lifter. Does anyone know of a lifter that will work in these engines?
The other option is to install a cam and mushroom style tappets from another Lycoming engine series. I have heard that this is possible, but that it is necessary to machine the case for the new lifters. Anyone know anything about this?
I am also open to other suggestions.
I've purchased "airboat lifters" from Aircraft Specialties for a very good price. They're ones that don't pass inspection because of some slight blemish that has no effect on their useability. Never had a problem with them in over 2,000 hours.
 

Richard Roller

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If I recall right, that's the engine that the Bendix dual magneto was developed for. A magneto that has one drive assembly, with an impulse coupling that drives two magnetos in the housing. It sounds real good until you realize that all your power is dependent on that one impulse spring. Those springs have a habit of corroding and breaking, and that knocks the spark on both mags back to TDC or close to it, and the engine makes noise but that's about all it does. You're not going very far.

Continental bought Bendix. They immediately discontinued making those mags and the parts for them, since only Lycomings used it. There are going to be some desperate owners at some point as these things wear beyond repair. There is only one magneto mounting pad on the engine, too, so you can't just install two separate mags.

We had one on an O-540J3C5D (Cessna R182) and it was a real pain to get off and on and to get the internals timed just right. I sure don't miss it. By the time I got it out, inspected and set up wit new points and stuff, and back in again, I was badly scratched up. They bury those things in some installations.

View attachment 132098

By the time the OP gets his H2AD engine fixed up right, including a mag overhaul, me might have spent enough money that he could have traded his H2AD core in for something much more popular and trustworthy and already overhauled..
I first encountered the dual Bendix mag on a '72 or '73 Cardinal RG. It had a O-360 engine. Oddly we never had any troubles with the mag. We put over 2000 hrs on that engine. On the other hand when we started working on the Skyhawks with the H2AD engine it was just one thing after another for the mag. Just like the engine.

Interesting note, a lot of the large radials had single drives for dual mags.
 

Bill-Higdon

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If I recall right, that's the engine that the Bendix dual magneto was developed for. A magneto that has one drive assembly, with an impulse coupling that drives two magnetos in the housing. It sounds real good until you realize that all your power is dependent on that one impulse spring. Those springs have a habit of corroding and breaking, and that knocks the spark on both mags back to TDC or close to it, and the engine makes noise but that's about all it does. You're not going very far.

Continental bought Bendix. They immediately discontinued making those mags and the parts for them, since only Lycomings used it. There are going to be some desperate owners at some point as these things wear beyond repair. There is only one magneto mounting pad on the engine, too, so you can't just install two separate mags.

We had one on an O-540J3C5D (Cessna R182) and it was a real pain to get off and on and to get the internals timed just right. I sure don't miss it. By the time I got it out, inspected and set up wit new points and stuff, and back in again, I was badly scratched up. They bury those things in some installations.

View attachment 132098

By the time the OP gets his H2AD engine fixed up right, including a mag overhaul, me might have spent enough money that he could have traded his H2AD core in for something much more popular and trustworthy and already overhauled..
Revmaster used them on some of their VW conversions
 

drwet

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Sep 21, 2021
Messages
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Here's an update. I obtained a lifter from a Ford. As it works out, most Ford V8 engines use the same lifter. Windsors and Clevelands are the same, including the Boss engines. FE blocks use a different lifter. Anyway, the Ford lifter is dimensionally identical to the Lycoming lifter! Still working out exactly what I am going to do, but but installing a set of high quality Ford lifters has definitely moved up my list. I think this is vastly preferable to the Lycoming 'T-mod' as it makes it a simple job to inspect and replace lifters. And about the most I can pay for them is $210 for a set of 16.
I am also still looking at the possibility of reconditioning the original lifters, so if anyone knows of a machine shop that still does this I'd like to hear about it.
 

TFF

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Aircraft Specialty does lifters and I have seen some machine shops that deal in vintage tractors. The tooling use to be relatively common, but as machine shops die out, they pitch them into the trash. When they grind the face the machine puts a slight curve into it. The lifters are not a weeble but they should wobble slightly on a flat surface. Rust is also the killer with the high contact pressures.
 

TFF

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You will have to do your own Google for others.
 

OKDon

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Here's an update. I obtained a lifter from a Ford. As it works out, most Ford V8 engines use the same lifter. Windsors and Clevelands are the same, including the Boss engines. FE blocks use a different lifter. Anyway, the Ford lifter is dimensionally identical to the Lycoming lifter! Still working out exactly what I am going to do, but but installing a set of high quality Ford lifters has definitely moved up my list. I think this is vastly preferable to the Lycoming 'T-mod' as it makes it a simple job to inspect and replace lifters. And about the most I can pay for them is $210 for a set of 16.
I am also still looking at the possibility of reconditioning the original lifters, so if anyone knows of a machine shop that still does this I'd like to hear about it.
Ford lifters like this?
 
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