Global engine (Half VW)

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Bipenut

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Oct 8, 2016
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Hello all,
I purchased a Preceptor N-3 Pup, the airframe is in great shape although it hasn't flown in about 6 years. It has a global half VW engine that the previous owner has torn apart and never got back to putting it back together so I purchased the project as airframe with a box of engine. I have built a few full VW engines and I am a GM trained mechanic so I have confidence that I will have no problem putting this engine back together but I have a couple of questions:

1) I have looked over the engine block, cylinders and heads for any hint of whether it is a 30hp or 40hp engine and I cant find any tags or markings on the engine anywhere, how can I tell which engine I have? Measure the bore of the cylinders? Or is there an easier way?

2) Where can I buy parts for this engine? I want to replace the bearings, rings and get gaskets for it.

Thank you for your time!!
 

Aerowerx

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Hello all,
I purchased a Preceptor N-3 Pup, the airframe is in great shape although it hasn't flown in about 6 years. It has a global half VW engine that the previous owner has torn apart and never got back to putting it back together so I purchased the project as airframe with a box of engine. I have built a few full VW engines and I am a GM trained mechanic so I have confidence that I will have no problem putting this engine back together but I have a couple of questions:

1) I have looked over the engine block, cylinders and heads for any hint of whether it is a 30hp or 40hp engine and I cant find any tags or markings on the engine anywhere, how can I tell which engine I have? Measure the bore of the cylinders? Or is there an easier way?

2) Where can I buy parts for this engine? I want to replace the bearings, rings and get gaskets for it.

Thank you for your time!!
I'm by no means an expert, but have done some reading on the VW engines while researching for my own projects. What I would do in your situation is measure the cylinder bore and crank length to get an idea of the displacement. Then look at Great Plains or Hummel Engine web sites to see if you can match up the numbers.

They may also have the parts. Or possibly stock parts could be used?

From what I have read, the higher 48 HP half VW engines are not as reliable as the 30 or 40 HP.
 

Hot Wings

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2) Where can I buy parts for this engine? I want to replace the bearings, rings and get gaskets for it.
!
Other than the stock VW based parts I don't believe you can no longer buy any of the Global specific parts. For the VW parts they can be purchased through any of the normal VW parts purchasing options. Just do your due diligence to try to avoid some of the cheap junk being offered to the performance VW trade.

As for rings - I wouldn't bother unless there is zero wear in the cylinders. Measure your cylinders for bore and spigot diameter* then buy a set of complete piston and cylinders to fit.

* Big bore kits come in several 'flavors'.

Edit: Aerowerx mentioned the stroke - which I forgot. There are 2 'flavors' of piston sets. One is for stock stroke cranks and the other has the pin height offset for longer strokes - specifically 82mm stroke. I suspect, but do not know for sure, that the Global used the short stroke pistons with barrel spacers (or a taller deck height) to match the 78mm stroke. After a quick search it appears that the Global 40 hp used the 94mm cylinders. If it were me, and the case were bored for the 92mm cylinders, I'd try to find a set of thick wall 92's that use the 94mm spigot diameter. They tend to be much more durable than the thin 94's.
 
Last edited:

Dana

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As far as I know the Global engines were all 35HP. Scott Casler at Hummel Engines is the reigning expert on half VW engines and can probably help you ID the correct parts.

Dana

P.S. Thread moved to the "Half VW" section.
 

N8053H

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I agree with Dana. Scott Casler would be the person you need to speak with if you have any questions. There should be a counter weight out on the prop or prop flange. If it's not there Scott can set you up with what you need. Each engine 38 hp, 45 hp use different counter weights.

I to am a trained engine tech. But seeing how this is an aviation engine and a conversion at that. I sent mine to Scott to have rebuilt. He would know if something was a miss and I may miss this. He did find a couple issue with my engine. The block had a crack in it. I knew oil was leaking and could never find it. He did.

Congrads on your new purchase. I too came across one of these Pups with a Mosler on it. I was amazed how smooth these moslers run. I really do like them and the Pup.

Tony
 

Bipenut

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First off, thank you for moving this thread to the proper spot! So is Scott a member of this forum? I would love to talk with him about this engine. I have heard that these engines do run smoothly. Yes this engine does have a counter weight and was marked where it was on the prop, is the counter weight prop specific or crank specific? Meaning was it used to balance the engine or prop?
Thank you all for your help!
Dennis
 

Hot Wings

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Ok thank you, I will contact Scott. I figured the counter weight was intended balance the engine.
The external weight is there to 'balance' the crank. There is another internal weight on the other end of the crank to match. The purpose of these weights is to help counter the Y axis rocking that opposed 2 cylinder engines have. In theory the weights should be different for each combination of recripocating masses. There are ways to do this with all internal parts but the way Hummel does it is simple and arguably lighter and cheaper.
 

Bipenut

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I was also wondering where to find a prop for this engine, the prop that came with it is a 58x23 prop and from what research I have done it should be a 54x24 so it seems to me to be over propped, also where the original owner was storing the prop was right underneath a pellet stove and caused the varnish to peel from one tip. I know the prop can be repaired but I would just rather replace it.
 

StarJar

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Maybe cutting off 2" from each tip and balancing it would give you a prop to start with.
BTW I think 54" is the absolute max, otherwise you get into tip speed/rpm issues with this engine. Even the full vw don't go to 54" usually, but the full vw can make a little more rpm under load. Therefore the 1/2 vw prop can be slightly longer than a full vw prop.
 

Bipenut

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As far as I know the Global engines were all 35HP. Scott Casler at Hummel Engines is the reigning expert on half VW engines and can probably help you ID the correct parts.

Dana

P.S. Thread moved to the "Half VW" section.

I agree with Dana. Scott Casler would be the person you need to speak with if you have any questions. There should be a counter weight out on the prop or prop flange. If it's not there Scott can set you up with what you need. Each engine 38 hp, 45 hp use different counter weights.

Thank you guys for the referral!! I just got off the phone with Scott, very informative person! I will be sending Scott my crank, rods and pistons to him to have them balanced and have him replace the bearings. I will also be getting some other parts for the engine from him.
 

N8053H

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Go with Tennessee Prop for a prop. Call Steve and tell him what you have and need. He will make you a prop. He stands behind his work too. A very nice man to deal with. IMHO. Be careful if you buy a used prop. Tennessee makes these props in a couple different flavors. Meanin blade width. You want a narrow tipped Blade. If dealling with Steve at Tennessee prop it won't be an issue, he will make you the correct prop for your engine. But buying a used one you need to know that these do come in different blade width's.

This year I did some experimenting with different props and blade profiles. For your 38 hp engine stick with a 54x24 narrow tipped prop. On my 42hp version of the same engine after testing I ended up with a 52x28 prop. I get the same numbers as to RPM and MP readings as using a 54x24 wide tipped prop. But with the 52x28 I get a little more speed out of the airplane. Fuel consumption went up some but that means I am getting more work out of the engine. I still have not decided if this was worth the extra few MPH. If I was to do it all over again, I think I would have stuck with the 54x24 wide tipped or bladed prop for my engine. Live and learn.

Tony
 

Bipenut

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Grand Coulee Wa.
Thank you Tony, I will give them a call. I wasn't really wanting to purchase a used prop, I just didn't know which way to turn for my best options. I just looked at their web site and looks great and just what I need.

Dennis
 

weasel

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Brooksville
Tennessee propellers makes a good prop. We ran one on the Legal Eagle for a while. I also have had a great experience with Frank from Performance Propellers USA. Custom built a nice prop for the Classic. Not a real great picture but you can see it here.

 

Propman

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Donie, Texas / Texas
Maybe cutting off 2" from each tip and balancing it would give you a prop to start with.
BTW I think 54" is the absolute max, otherwise you get into tip speed/rpm issues with this engine. Even the full vw don't go to 54" usually, but the full vw can make a little more rpm under load. Therefore the 1/2 vw prop can be slightly longer than a full vw prop.
With the VW, be it half or full. Prop diameter can go to 62" without issues. On the half, HP and ground clearance will dictate diameter. For the 45 HP that Scott builds i craft a 56" diameter and the pitch is dependent on the airframe its bolted too. I make several of these a month and have excellent results.
 

Dana

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With the VW, be it half or full. Prop diameter can go to 62" without issues. On the half, HP and ground clearance will dictate diameter. For the 45 HP that Scott builds i craft a 56" diameter and the pitch is dependent on the airframe its bolted too. I make several of these a month and have excellent results.
62" on a half VW?

Dana
 
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