# Build your own VW engine

Discussion in 'Volkswagen' started by Streffpilot, Nov 19, 2018.

### Help Support HomeBuiltAirplanes Forum by donating:

1. Nov 27, 2018

### Vigilant1

#### Well-Known MemberHBA Supporter

Joined:
Jan 24, 2011
Messages:
3,909
1,721
Location:
US
I sure ain't Pops, but from the photos it looks like Scott Casler uses Force One bearings/hubs on his 1/2 VWs. Another bit of info is that no one (to my knowledge) has been able to build a reliable PSRU for these 1/2 VW engines, the amplitude of the torque pulses (compared to a 4-cyl) are more severe. My guess is that such a PSRU is possible (after all, folks build airplane PSRUs for two-cyl BMW 1200 CC motorcycle engines, but the ones that work usually contain a clutch and some well-engineered dampers). I'd expect that pounding to be felt at the front bearing and esp at the "thin spot" in a conventional crank where the Woodruff key and the tapped hole in the end of the crank reduce the amount of available "meat," and that is where failures can occur. This has generally not been a problem with non-stroked 4 cyl engines. The Force One hub and bearing greatly reduces crank stress at this point. .

The Force One Hub and bearing add about 200 over the cost of the shrink-fit prop hub alone. And, there is a cost to do the machining of the case for the Force One (but the e case will need to be worked on anyway at a shop if larger cylinders are to be used). It is pretty cheap insurance. FWIW, GPAS does sell a shrink-fit hub for the 1/2 VW. See here. Last edited: Nov 27, 2018 Pops and poormansairforce like this. 2. Nov 27, 2018 ### poormansairforce ### poormansairforce #### Well-Known Member Joined: Mar 28, 2017 Messages: 610 Likes Received: 131 Location: Just an Ohioan Vigilant1, thanks for that info. If Scott uses them then that answers my question especially since I would build a stroker. My desire would be direct drive but the PSRU talk does raise a question but that's for another thread. 3. Nov 27, 2018 ### N8053H ### N8053H #### Well-Known Member Joined: Jan 31, 2013 Messages: 2,518 Likes Received: 439 Location: Right here in front of my computer You must also use a wooden prop on a 1/2 vw. Don't go dual carbs but use a single updraft carb. 4. Nov 27, 2018 ### Vigilant1 ### Vigilant1 #### Well-Known MemberHBA Supporter Joined: Jan 24, 2011 Messages: 3,909 Likes Received: 1,721 Location: US Wood props are mandated by all VW engine mfgr and kit suppliers except Revmaster. 5. Nov 27, 2018 ### Pops ### Pops #### Well-Known Member Joined: Jan 1, 2013 Messages: 7,023 Likes Received: 5,920 Location: USA. Used to be a local Ultralight field about 50 miles away with lots of 1/2 VW Mini-Max's and etc. Friend of mine flew a MM with a 37 hp 1/2 VW I was thinking 1000 hrs but was talking to him on the phone a couple days ago and he said he put 1200 hrs on the engine before taking it apart and checking it for wear. Also said he has 2200 hrs flying behind a 1/2 VW. He builds and balances his own engines and they are very smooth. I know that he just uses the GP's prop hub for 1/2 VW. I really don't know if Scott uses the Force one hub on his 1/2 VW's or not. I built a 37 Hp 1/2 VW about 10 years ago and used GP's prop hub, but if I was building another I think I would go with the Force One hub. Same if I was building another 1835 cc , engine with the prop hub on the pulley end. 6. Nov 28, 2018 ### poormansairforce ### poormansairforce #### Well-Known Member Joined: Mar 28, 2017 Messages: 610 Likes Received: 131 Location: Just an Ohioan Yep, I got all of that. I'm trying to stay away from multiple carbs anyway as well as redrives. Keep it simple by hand propping as I have had all kinds of electrical issues on various vehicles. I don't need that on an simple airplane. Thanks. 7. Nov 28, 2018 ### poormansairforce ### poormansairforce #### Well-Known Member Joined: Mar 28, 2017 Messages: 610 Likes Received: 131 Location: Just an Ohioan Thanks. Good to hear you confirm the Force hub. I would have loved to have seen or heard the results of that 1200 hr engine. 8. Nov 28, 2018 ### Pops ### Pops #### Well-Known Member Joined: Jan 1, 2013 Messages: 7,023 Likes Received: 5,920 Location: USA. He said very little wear and went ahead and put in new bearings , piston, ring, cylinder set and new exhaust valves and guides. poormansairforce likes this. 9. Nov 28, 2018 ### Vigilant1 ### Vigilant1 #### Well-Known MemberHBA Supporter Joined: Jan 24, 2011 Messages: 3,909 Likes Received: 1,721 Location: US Just for convenience, here are the bore/stroke/displacement and HPs of the engine kits offered by Great Plains. [TABLE] [/TABLE] [TABLE] [TD="align: center"]FRONT DRIVE SPECS [/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]TYPE 1[/TD] [TD="align: center"]ENGINE DISPLACEMENTS[/TD] [TD="align: center"]1600[/TD] [TD="align: center"]1700[/TD] [TD="align: center"]1835[/TD] [TD="align: center"]1915[/TD] [TD="align: center"]2180 [/TD] [TD="align: center"]2276[/TD] [TD="align: center"]Take off HP, 3600 RPM (MAX)[/TD] [TD="align: center"]55[/TD] [TD="align: center"]60[/TD] [TD="align: center"]65[/TD] [TD="align: center"]69[/TD] [TD="align: center"]76[/TD] [TD="align: center"]80[/TD] [TD="align: center"]Continuous HP, 3400 RPM[/TD] [TD="align: center"]50[/TD] [TD="align: center"]55[/TD] [TD="align: center"]60[/TD] [TD="align: center"]65[/TD] [TD="align: center"]70[/TD] [TD="align: center"]76[/TD] [TD="align: center"]Bore (mm)[/TD] [TD="align: center"]85.5[/TD] [TD="align: center"]85.5[/TD] [TD="align: center"]92[/TD] [TD="align: center"]94[/TD] [TD="align: center"]92[/TD] [TD="align: center"]94[/TD] [TD="align: center"]Stroke (mm)[/TD] [TD="align: center"]69[/TD] [TD="align: center"]69[/TD] [TD="align: center"]69[/TD] [TD="align: center"]69[/TD] [TD="align: center"]82[/TD] [TD="align: center"]82[/TD] [TD="align: center"]Displacement, in CC[/TD] [TD="align: center"]1584[/TD] [TD="align: center"]1700[/TD] [TD="align: center"]1834[/TD] [TD="align: center"]1915[/TD] [TD="align: center"]2180[/TD] [TD="align: center"]2276[/TD] [TD="align: center"]Compression Ratio[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]8.0: 1[/TD] [TD="align: center"]Minimum Fuel Octane[/TD] [TD="align: center"]92[/TD] [TD="align: center"]92[/TD] [TD="align: center"]92[/TD] [TD="align: center"]92[/TD] [TD="align: center"]92[/TD] [TD="align: center"]92[/TD] [TD="align: center"]Firing Order[/TD] [TD="align: center"]1234[/TD] [TD="align: center"]1234[/TD] [TD="align: center"]1234[/TD] [TD="align: center"]1234[/TD] [TD="align: center"]1234[/TD] [TD="align: center"]1234 [/TD] [TD="align: center"]Magneto[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Slick[/TD] [TD="align: center"]Propeller Drive[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]1.1[/TD] [TD="align: center"]Carburetor, Float Bowl[/TD] [TD="align: center"]1617[/TD] [TD="align: center"]1617[/TD] [TD="align: center"]1819[/TD] [TD="align: center"]1819[/TD] [TD="align: center"]2122[/TD] [TD="align: center"]2122 [/TD] [/TABLE] There's another VW Type one engine not shown here, it is the Revmaster model R2300. The unique thing about it is the 84mm stroke, they must use a special custom crankshaft and even more aggressive clearancing of the case. Like other Revmaster engines it has their proprietary alternator and ignition setup, their special large front bearing, and their proprietary RevFlow carburetor (no float bowl, similar to the Sonex AeroInjector or the Posa carb in concept). Lots of power at lower RPM is the claim (= more torque at an RPM that should allow for a longer prop than other VW engines) Web page with specs: http://revmasteraviation.com/?p=308 Price (completely assembled and test run, per their web site):9,400
Displacement: 2331
Takeoff RPM/HP: 85 HP at 3350 RPM (elsewhere they say 85HP at 3200)
Continuous RPM/HP: 80HP at 3000 RPM
Bore: 94mm
Stroke: 84mm
Compression Ratio: 8:1

I noticed in some of the racing VW catalogs that the 84mm crank is an available size, and I'd guess they also stock conrods and pistons that work. Now, if we set up the engine to use this stroke but with 92mm cylinders we'd have an engine of 2234cc that avoids the thin-wall 94mm cylinder problems. We probably wouldn't want to turn it faster than about 3300 max with a stroke like that, maybe 3000 continuous, but I'd think it would make about 80 HP for takeoff, 75 HP continuous if we can keep the temps in line), and the longer prop would give us more thrust.

Still, it would be a lot of work for the additional 5 HP, and it would be uncharted territory.

Last edited: Nov 28, 2018
10. Nov 28, 2018

### Pops

#### Well-Known Member

Joined:
Jan 1, 2013
Messages:
7,023
5,920
Location:
USA.
11. Nov 28, 2018

### lakeracer69

#### Well-Known Member

Joined:
Dec 10, 2008
Messages:
129
55
Location:
New Hampshire
A quick question on Zenith carbs, Great Plains (GP) has their own numbering system for these carbs. It is all very confusing for anybody. Maybe Pops can answer this one.

For instance, GP lists the 1819 carb for an 1835cc engine. Which Zenith model number is it? Google hasn't been much help with this, STUPID GOOGLE! Hehehe

12. Nov 28, 2018

### Vigilant1

#### Well-Known MemberHBA Supporter

Joined:
Jan 24, 2011
Messages:
3,909
1,721
Location:
US
Yep, but that project has been on hold for about a decade. I think Joe Horvath built a few for his dragsters and there were a couple prototypes in airplanes.

13. Nov 28, 2018

### Pops

#### Well-Known Member

Joined:
Jan 1, 2013
Messages:
7,023
5,920
Location:
USA.
The part # on the Zenith carbs is very confusing. The carbs that GP are selling is the 68 Series. I really don't know a lot about sizing the carb to the engine and buying the carb from GP's is a sure way of getting the correct carb but you pay for it in the added cost of the carb. I sure don't want GP's to go out of business.
In my thinking, the venturi size of the carb should be close to the intake valve size used, but I am sure there are people on this site that knows all about it.
I think the Zenith carb is the best carb on the market for the VW. I have tried the slide carbs and Zenith is a far better carb in my view. If the Zenith had the cockpit adjustable mixture with fuel shutoff like a MS carb it would be great. You can put a flex cable to the carb and make a bracket to turn the mixture screw but it would be nice to have an arm on the carb like the MS's on the Lyc, Cont.

14. Nov 28, 2018

### poormansairforce

#### Well-Known Member

Joined:
Mar 28, 2017
Messages:
610
131
Location:
Just an Ohioan
More questions:
If one was committed to lightening a 1/2 vw how much weight could be removed from a case by removing all material that is not needed? How much does a mag weight? Is drilling out a crank going too far? Removing the oil pan area and replacing with a sheet metal pan? Will the low CR allow for auminium rods? I'll probably get spanked for these ideas but had to ask I just see a 1/2 vw as a superior engine to an industrial engine.

15. Nov 28, 2018

### N8053H

#### Well-Known Member

Joined:
Jan 31, 2013
Messages:
2,518
439
Location:
Right here in front of my computer
After stumbling into the problems I am having with my vw I have learned a little about zenith carbs. Zenith carbs have a 5 digit number stamped into the float bowl. This number will be in a circle configuration. Mine is 12566. The first two number tell the size 12. If you go up one size you will get into the number series 13xxx and so on. There are three different sizes of these updraft carbs. The 68 series is the smallest and the first one pictured on GP website. It has the HSM " High Speed Mixture " adjustment screw that comes out straight from the float bowl. The next one they show has this HSM screw coming out at an angle. That is the next size up from the 68 series. Scott Casler gave me this education on Zenith Carbs. I forget what series or model my engine needs but the 68 series is not it. But like Pop's said Zenith Carbs are very confusing at best. What I have learned only scratches the surface when it comes to the numbering system Zenith uses. I also found this info searching the web, but I did not save it. If I come across it again I will post a link.
If you screw this HSM screw all the way in your engine will die. The carb will run out of fuel in the float bowl and it will stop. This is how I shut my VW down at the end of each day.

Pops likes this.
16. Nov 29, 2018

### Daleandee

#### Well-Known Member

Joined:
Sep 11, 2015
Messages:
875
552
Location:
SC
While I've never run a Zenith carb I agree on the idea as I have run a slide carb (Aerocarb) and a float carb (Marvel Schebler) and find the difference to be quite phenomenal as to reliability and ease of setup/tuning. The MS requires carb heat but in my experience it's well worth it.

But I was wondering if anyone has ever thought to try a small Marvel Schebler on a VW conversion. Not sure what size would be needed but I would think something from an A-65 might be in the ball park. Some have an accelerator pump (think primer) and (as Pops noted) a real mixture control.

Dale
N319WF

Pops likes this.
17. Nov 29, 2018

### Pops

#### Well-Known Member

Joined:
Jan 1, 2013
Messages:
7,023
5,920
Location:
USA.
So we know that your #12566 would be the correct Zenith carb for the 1600/1750 cc VW engine, is that correct?

The smallest Marvel Schebler carb that I know of was used on the old 65 HP Lyc. Might be about right for the 2180 cc VW ? I stored an airplane in my hanger for many years for a friend. It was a Piper 1938 J-3 Cub Sport that came from the factory in April of that year with the 3 piece windshield, tail skid, and a 65 HP Lyc engine. Landing gear and tail surfaces were the same as the J-2, and had 1937 Plymouth auto master cylinders for the brakes on the bottom/outside of the fuselage. Had a small Marvel Schebler carb on the Lyc.

Last edited: Nov 29, 2018
18. Nov 29, 2018

### Vigilant1

#### Well-Known MemberHBA Supporter

Joined:
Jan 24, 2011
Messages:
3,909
1,721
Location:
US
Dale,
What's the reported advantage for the M-S over the Zeniths? I noticed that the used (overhauled) M-S start at $699 at Aircraft Spruce, and a kit of gaskets, springs and parts to overhaul the M-S carb yourself sells for$436. Are they made of platinum, perform better, or is this the "aircraft quality" surcharge?

19. Nov 29, 2018

### Pops

#### Well-Known Member

Joined:
Jan 1, 2013
Messages:
7,023
5,920
Location:
USA.
20. Nov 29, 2018

### Daleandee

#### Well-Known Member

Joined:
Sep 11, 2015
Messages:
875
I found a used Marvel Schebler for $650.00 for the Cleanex. Was gonna send it for rebuild but it has been flawless since the first start. I did have to set the idle down as the engine broke in. But to answer your question ... yes they are quite proud of their carbs and parts. Last I heard a rebuild on a core can be had (parts & labor) by a certified rebuilder for about$600.00. But for the reliability and flawless service I have received from it ... I'd consider that to be money well spent.