# Steps to scratch build a VW

Discussion in 'Hangar Flying' started by Little Scrapper, Aug 13, 2019.

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1. Aug 27, 2019

### Vigilant1

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I wonder: Does the "drill and tap for full flow" mean simple removal of the plug in the gallery leading to the #4 bearing, or is it all the case-related HVX mods?

2. Aug 27, 2019

### Hot Wings

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I'd ask specifically about this. $80 for just the one hole is too much money, IMHO, and he can do the work .... in about 4 minutes if the tap is in the tool box. Grinding the case on the nearby oil line boss to clear the fitting, if you use a 90, takes a little longer. If the$80 replaces all of the press in plugs with threaded it's a good deal.

The picture of the case looks like a standard universal case. Some cases come with added material behind #3 so they don't need welding. Welding behind #3 is a reasonable thing to do with 94mm cylinders but if the case doesn't need welding that is even better.

3. Aug 27, 2019

### lakeracer69

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Upon first glance I would have thought it was everything including the plugs. If it's not then, not quite as good of a deal for some one who has the tap and drill bit.

Looks like aluminum plugs are best for no leaks because of similiar expansion rates.

4. Aug 27, 2019

### Little Scrapper

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I have the drills and taps needed.

For me it's about the education, not the money. It would be nice to have a thread here on HBA that actually produces a engine, that would be cool.

The description of the engine says it's strengthened behind #3 unless I read it wrong.

5. Aug 27, 2019

### Little Scrapper

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Is this it? I'm assuming there's just one company casting these and they all just use this manufacturer, whoever that is?

6. Aug 27, 2019

### Hot Wings

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I don't know how may companies are actually casting the mag/alum alloy cases or what is available at the moment.

The deep stud #3 was a VW OEM modification that arrived around 1972. (can't remember the exact year) This was due to cracking with stock size cylinder bores, even though it was rare. I've never seen a cracked case with a stock bore.

When we started cutting the case for the larger cylinders this became a relatively common problem. The after market fix was to fill up the area under #3 with weld material. It works but the amount of welding needed tends to warp the case. A line bore fixes this but a lot of the cases get to market with welded #3 and no line bore.

There have been cases on the market that bypassed the welding stage and simply cast the block with the extra material already in the #3 web. This obviously removed the need for a post production line bore. I do not know if this style of case is still on the market.

So in summery there are/were 3 versions of the modified #3 case.
1) Stock deep stud only - which from the description and photo seems to be this particular case
2) Deep stud with a welded #3 web
3) Deep stud with a cast thick #3 web.

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7. Aug 27, 2019

### Little Scrapper

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Interesting. Let me add some complexity here. I'm finding out there's 3 part numbers for the AS41 case which is the OEM Brazil/Mexico version. Possiblity China?
Air-cooled.net = 043-101-0250E $800 CB performance = 043-101-0250E$985
MOFOCO = 043-101-0250D $1,000 SCAT= 043-101-025$\$755

So there's a E and a D somehow as well as no letter designation. Anyone know why or what this is about?

I can call and ask them, maybe I'll try and do that today

8. Aug 27, 2019

### Hot Wings

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I never tried to memorize VW part numbers. I even made up a flow chart back in the day to figure out what points/condensers to use - Distributors got swapped all the time and there were about 6 versions of each part. Some suppliers/distributors even made up their own "VW" part numbers to distinguish their own modifications of the base part.

The last letter of a VW part number is the particular version and the preceding 3 numbers are the general part configuration. If there have been no revisions of the part there is no suffix. This all works out just fine when only VW was making the numbers. When the aftermarket started making up their own numbers to describe their proprietary version of a part it introduced a lot of ambiguity to the market.

Using the VW system the -025 would probably be a basic universal case. A modification, like a change in alloy or other small casting change would be - 025A. The next change -025B.

I can't explain a 4 digit number with a letter modifier.
https://www.aircooled.net/vw-part-numbers-explained/

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9. Aug 27, 2019

### Pops

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As usual, Hot Wings is right on.

10. Aug 27, 2019

### Pops

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Buying a new case, if you don't drill all the plugs out and tap, there is no way you know if the oil gallerys are free from metal shavings.
I would buy the #3 and not have to worry about a warped case from welding. (Deep stud with the cast thick #3 web)

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11. Aug 27, 2019

### Little Scrapper

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One of the issues I see as a total VW novice are some of the notes I see on these websites. Here's a screenshot. Clearly there's more than one company casting these cases This screenshot is from air-cooled.net

For anyone who's new to the VW world things like that are a bit concerning simply because there's no "go to" reference for making the right decision.

With this particular thread if like to go through these issues one at a time so the next guy doesn't have to. So I'm gonna make some calls and see what I can come up with. I'll post updates.

Mike

12. Aug 27, 2019

### dmar836

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Bet you money they will ask what you have now and what you are putting it in. Not unreasonable for assisting a novice car guy but...
I have yet to feel the need to weld behind the #3 cyl. The universal case you have selected is about as far as they advanced for factory vehicles. This is the lighter magnesium, is dual relief, has the extra "universal" bosses for multiple vehicles(or for other accessories), has the deep running stud in #3(this will be an obvious thing once you see it), and the case savers installed. As long as you are getting it for 8mm cyl/head studs, I wouldn't have any issues starting right there. If I was building a drag bug then maybe I'd go the extra cost for weld or cast behind #3. I just haven't heard the car guy's block concerns filter into the AC world - just as the car guys aren't concerned at all about the pulley end of the crank breaking off on the strip.
The advice for ensuring the casting is cleaned out is valid but you could also drill and tap the plugs with the Empi plug kit. This allows you to mod the case for HVX mods or to add full flow filtration later if you desire - all while enabling you to clean out the block. You'll want to do that whether you pay to have them tap all the plugs or not.
JMO,
Dave

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13. Aug 27, 2019

### Pops

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I always buy the Empi plug kit + I have a stash of assorted plugs.

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14. Aug 27, 2019

### blane.c

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How do you know you are getting the #3 type case? Per usual marketers are barking there product and muddying the water as much as possible at the same time.

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15. Aug 28, 2019

### Vigilant1

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There has been a good "go to" reference for these things, and it remains available to us all.
There have been a few companies that have specialized in selling VW aftermarket products to people building aircraft engines. I have no financial interest in Great Plains, Scott Casler, Sonex, Revmaster, etc but just want to point this out: IMO, they have performed a valuable service to the homebuilt community by screening out crummy parts (and there are a lot of them out there) and also in assuring that the parts do what they claim to do. They have, of course, sometimes made mistakes, and IMO they don't all hold to the same standards. But, on the whole, they have been a real asset to the homebuilder community--answering questions specific to using VW engines in airplanes, making books and DVDs available to those building VW engines for aircraft use, etc. Many of these companies are no longer around (HAPI, Mosler, etc), but a few remain. We can talk to them and don't need to be coy about what we are going to use the engine for.
Yes, it is often possible to save some money by buying VW parts from a company that isn't involved with the homebuilt aircraft community. I have done it and will probably do it again. But, when I can, I am happy to do business with companies that are helping to assure these engines remain a resource available to the next generation of aircraft builders. It's not wrong to buy from others, but I just wanted to express this opinion. Even in the age of the internet, I think it is valuable to have real companies which can do the research and have the experience to help us sort the wheat from the chaff, who can build kits for those who want them, and who will publish helpful guidance for use by our community.

Last edited: Aug 28, 2019
16. Aug 28, 2019

### blane.c

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Are the mount holes really this messed up or is it a bad example?

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17. Aug 28, 2019

### dmar836

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I’m not against the companies that make VW conversions but I do have to say I don’t think the problems people have had with VWs is necessarily due to crummy parts. I doubt the pistons, cylinders, rings, bearings, valvetrain, pushrods, lifters, etc are proprietary parts. Not being critical of the comments at all but I think it is more likely that people cheap out or select inappropriate parts. You are correct- that’s what a “pre-selected” parts kit avoids. In addition, the building of the engine is a decent part of it and,at least as far as GP and AeroVee go, a step by step manual for “their” parts helps that a lot.
I know a guy who has been through 8-9 engines of all types and has landed every one off airport or crashed after they burn up. Things like placing radiators against the firewall and things like that. He just won’t listen to anyone and unfortunately he will likely die from this. Do I think a guy like that checks ring gap or calculates correct pushrod length? Actually, I think he just assumes a used engine is good.
His escapades also remind me that the ability to fabricate correctly(also not overbuilding) will avoid a lot of failures too.
Dave

18. Aug 28, 2019

### Little Scrapper

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Fair enough. This thread is about scratch building a VW like people have for decades. I'm a big fan of any company that supports aviation.

But here on this thread I'm interested in building a engine from scratch. I want to learn which parts are best and why. I want to discover this for myself using knowledge of others on the forum. I want to share what I learned with others new to aviation and those just interested in doing something worth doing.

There's not only nothing wrong with that it literally is what homebuilding is about and has been about since day one. I think we've forgotten this. The process is the product for me. I'm a lifetime learner and when I find out there's some confusion about what case yo use, as an example, I'm interested in learning why.

Again, these "go to" companies have been mentioned in this thread a few other time and that's not what this is about. I have little Interest in ordering a kit and assembling. If that were the case I'd just order up a RV.

Honestly, if it costs me double I really don't care. In all my posts here since I've been a member on the forum I'm interested in one thing only, education.

So let's find out which is the best case and why? And let's share it and grow aviation in the process, make some new friends and contribute to something bigger than ourselves. Then move to the next step.

What else could be better than that?

Last edited: Aug 28, 2019
19. Aug 28, 2019

### Vigilant1

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There's absolutely nothing wrong with that. I hope I haven't given the wrong impression.
I sensed some frustration/confusion about the quality/utility of particular parts (cases, etc). This happens all the time with VW aftermarket parts, because manufacturers change, retailers change their suppliers for the same parts (sometimes without specifying who makes the parts, etc). (This happens a LOT with VW cylinder heads). If you identify the best parts for your project now--manufacturer and retailer--there's a >very< good chance that these same retailers, part numbers, etc won't be much good at all to someone trying to follow in your footsteps in a few years. It's just the nature of this supply chain. Every little part is critical--ask anyone who has had a pushrod tube split.

For years there have been a few companies who made it their business (literally) to find and sell parts that were appropriate for VW-derived aircrat engines, and to explain how to use them. I can look in the GPAS catalogue, read about/compare options that might be suitable for a VW airplane engine, call and talk to them about my project, and have them sell me a part that I can count on to work. Scott Casler also won't sell junk, and neither will Revmaster. Example: There's only one source in the world for a ready-made pulley-end prop bearing and hub for stroker VW engines: GPAS (and Scott Casler buys from them). They don't charge a lot for that part, and it's a small market. If their light should blink out, building VW engines gets harder for a lot of folks.

I don't have any objection to folks building up their engine by buying parts from hotrod shops. But that will require doing the research on each part to determine its suitability and quality, and that knowledge has a short shelf life. We can all learn something by discussing these choices, I know I will. But there will be, now and in the future, folks more interested in building an engine than in researching each part, and I hope they'll continue to have a few airplane engine VW "clearinghouses" that can help them sort gold from junk, and sell 'em parts they can trust without requiring that they do hundreds of hours of internet research before starting on their engine build.

Last edited: Aug 28, 2019
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20. Aug 28, 2019

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