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VW / Chevy 8 cylinder open source project.

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dirk_D

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Victoria, Australia.
Hi all, I was off topic on twin VW thread https://www.homebuiltairplanes.com/forums/volkswagen/7350-8-cylinder-vw.html and felt this idea may deserve a thread of it's own.
The idea is for a Chevy crank/cam/rods/lifters packaged in a VW type 1 or 4 pattern engine case.
Using aftermarket VW barrels, a hefty boxer motor could be achieved - anywhere from 5 to 7 litre capacity.
With a 105mm stroke (roughly) that matches the largest stroke stuffed into a type 1 case.
The bore spacing is spot on (111.8 to 112).

I could not do this on my own, i was thinking it could be a community based project structured as such;
Contributions of scanned and hand measurements published online and openly discussed.
2d cad personal mailed amongst key drafting contributors.
Finally, all finalized 3d cad could be entrusted to the website https://www.homebuiltairplanes.com and sold to non contributors for a small donation fee.

Maybe a team of 3 or 4 cad draftspersons would get it done.
It would be cool!
 

Armilite

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Sep 5, 2011
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AMES, IA USA
Dirk:

I have to ask, WHY would you go to all the trouble? The VW 4 cylinder engine has a big following, in planes, cars, airboats, etc. Many aftermarket HD RACE parts. You can build a brand NEW engine from them. You can make a BIG BORE, add a TURBO, DUAL PLUG, FUEL INJECTION, etc. There are 3D models on www.grabcad.com of VW engines, parts, etc. How much HP do you want or need? An engine, that would lend it self to what you was thinking is the Continetal 0-200 base design, only using cheap HD RACING auto parts. Today, CNC machines are cheap, CAD/CAM software is powerful. Other small, high HP alternatives, is the newer 4 stroke SLED engines. Just make an adapter to use a gear drive. Most newer sled engines make 125+HP. Even the older 90's Sled engines that can be converted fairly easy, they already have the holes for the Rotax gear drive. A Skidoo/Rotax(91-98) 670 makes 90hp stock at 6400rpm. Only weighs 5-6 lbs more than a 582UL 65hp@6500rpm. Oh, I bought my used 670 engine complete, for $250. with a rebuild, new gear drive, I plan to have about $2500-$3500 in it, depending on what head, ignition, pipe I decide to go with.

Just my 2 cents
Rich Gillen
 

Topaz

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...It would be cool!
It would be cool, but the first thought that comes to mind for me is the same as Armilite's: Why? If the answer is, "because it's cool and I like a challenge", then go for it. But this is more than a drafting exercise. A lot of engineering would have to go into it and, as much as I'm a fan of VW engines, there are much better options in the power range of an "8 cylinder VW/Chevy"/
 

dino

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florida
I don't think the cranck and camshaft will work as the timing of a V-8 is different from a boxer. With 0 deg straight up TDC of a boxer's cylinders is at 90 and 270 whle a V-8's depend on V angle. For example a 90deg V-8 would have cylinder TDCs at 45 and 315 degrees. Plan on milling a cranck and cam or mating the VWs. Maybe running one VW with power take off at the clutch and attached to the other running off the cooling fan end of the cranck back to front. Each cranck would have a sprag clutch to decouple in the event of single engine failure. A shaft with belt sprocket would join the sprags. The belt would transfer power to a prop shaft supported above the engines and parallel to the crancks also acting as a PSRU allowing the engines to be run at higher speeds.

Dino
 

dirk_D

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Victoria, Australia.
I don't think the cranck and camshaft will work as the timing of a V-8 is different from a boxer
Technically, it still is a boxer with a 90 degree crank, just that the opposed pistons have moved apart 224mm, this would create a slight rocking motion, but manageable, Ferrari did it for years with the flat 12.

Plan on milling a cranck and cam
Not necessary, sure we are rotating one bank of cylinders down 90 degrees, but we are also doing the same for the lifters which automatically corrects the timing issue meaning no machining cranks, etc.
The whole idea is for near zero part machining, all parts being donor.

Not sure if type 4 is the same bore spacing as the type 1, but if it is - we could use Type 4 heads with clearance milled on opposing sides.
The cam would need its rotation reversed if we used type 4 heads, inlet and exhaust profiles would be swapped and need slight regrinding to match.

If a head was scratch designed, then the cam rotation would remain as it was in the chevy, and chevy parts would be used in the head. This is a much nicer option, being a clean sheet cylinder head it could gain a high port roof to really liven things up.
Apart from the barrels and pistons the motor would be a really light small block without the iron water jacket.


"why" criticism is a fair enough call and i do take it into account.
 

hogheadv2

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Feb 7, 2010
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Booger finger of Michigan
540 is near 9L, Just be pounding your head to a wall to build such a spare parts wind machine.
Collect up parts and put together a Exp. 470 with 2 crank trigger ign. systems. Be far happier.
 

dirk_D

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Sep 22, 2010
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Victoria, Australia.
540 is near 9L, Just be pounding your head to a wall to build such a spare parts wind machine.
Collect up parts and put together a Exp. 470 with 2 crank trigger ign. systems. Be far happier.
9 litres? yes please! What price though?

Maybe Scat or Revmaster might pick up the idea and run with it, at least the idea is out there now, hopefully it sparks a venture and is affordable.

I was wrong with the reverse cam rotation idea, type 4 heads are a no go.
 

Dan Thomas

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Sep 17, 2008
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It would be cool, but the first thought that comes to mind for me is the same as Armilite's: Why?
To get rid of lots of time and money. Many folks have already spent lots of time and money on developing new engines that never reached the market. Most of them never flew in an airplane. Some of them never even made any noise.

Dan
 

RJW

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Wisconsin and Kansas
Hi Dirk,

Cool idea. Sadly, it probably won’t work. Attached is a sketch of just what you are describing.
Boxer 8.jpg
As you can see there is no room for the center exhaust ports. Even if you were to cut and weld the heads to reroute the center exhaust ports the already poor cooling properties of the stock exhaust ports would be made much worse. The center exhaust valves would cook in no time.

Also to balance a 90-degree V8 crank a LOT of extra mass is needed. The use of a 90-degree crank in a flat 8 engine would wipe out the inherent balance and light weight of the 180-degree flat 8 configuration.

I’m unsure about the flat 12 you mentioned. What is the crank throw configuration on the Ferrari motor? It seems to me that it should be 60 degrees. This would result in a statically balanced motor and one with extremely good dynamic balance with very low weight.

Anyway keep thinking of weird stuff. It’s lots of fun, you will learn tons, and maybe even come up with a really cool something or other.:)

Rob
 
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RJW

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What about a radial version... two rows of four in an "X" planform?
Yes, an X motor would work using the center two throws of an SBC crank (these are at 180 degrees to each other).

If I am ever able to work out all of the gazillion details required to bolt this together, someday I would like to build this 10-cylinder radial.
VW Radial.jpg
The balance would be good and the thing would be cheap as hell once the rods, crankcase, etc. were worked out. The only thing weird about it would be the sort of uneven firing. It would have two power pulses spaced 36 degrees apart every 144 degrees.

Rob
 

Dan Thomas

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Yes, an X motor would work using the center two throws of an SBC crank (these are at 180 degrees to each other).

If I am ever able to work out all of the gazillion details required to bolt this together, someday I would like to build this 10-cylinder radial.
View attachment 17034
The balance would be good and the thing would be cheap as hell once the rods, crankcase, etc. were worked out. The only thing weird about it would be the sort of uneven firing. It would have two power pulses spaced 36 degrees apart every 144 degrees.

Rob
Your uneven firing is because you have the aft cylinders exactly in line with the front ones. A real two-row radial does it this way:
radial-engine-thumb1766693.jpg

Dan
 

RJW

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Your uneven firing is because you have the aft cylinders exactly in line with the front ones. A real two-row radial does it this way
Hi Dan,

That’s exactly right. It’s the price paid for using cheap, readily available parts. The alternative is cutting the heads, spacing them as in a normal two-row radial, and then fashioning custom cams or making entirely new and expensive cam rings. Do you think the weird firing of the stock in-line cylinders would cause unacceptable vibration problems? I really would like to do this engine someday in 100 or 120 horsepower. It seems like it would be a fun and cheap radial. But if combustion vibration is an issue then I will not pursue it.

Thanks,
Rob
 
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Dan Thomas

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Hi Dan,

That’s exactly right. It’s the price paid for using cheap, readily available parts. The alternative is cutting the heads, spacing them as in a normal two-row radial, and then fashioning custom cams or making entirely new and expensive cam rings. Do you think the weird firing of the stock in-line cylinders would cause unacceptable vibration problems? I really would like to do this engine someday in 100 or 120 horsepower. It seems like it would be a fun and cheap radial. But if combustion vibration is an issue then I will not pursue it.

Thanks,
Rob
The vibration might or might not cause problems. Don't know. But it wouldn't be very smooth in any case, and I suspect that the "fun and cheap" part would disappear pretty quick, too.

dan
 

revkev6

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massachusetts
I've thought about radials done this way before. I don't have any info handy but I do remember reading about several attempts to make them work with single cut down heads. never seen a two row attempt. Scat did make single cylinder heads for the VW at one point for racing. Pretty much the only thing they are used for these days is cut down vw aircraft engines. if you could find enough of the scat heads to make a radial then build the engine to go with it, you would probably be better off buying an M14 new/rebuilt
 

Himat

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I’m unsure about the flat 12 you mentioned. What is the crank throw configuration on the Ferrari motor? It seems to me that it should be 60 degrees. This would result in a statically balanced motor and one with extremely good dynamic balance with very low weight.
I remember there was a lot of discussion about the Ferrari Testarossa flat 12 engine at the time.
The engine is a flat 12, but not a "boxer" with two oposing cylinders firing at the sametime. The engine was often described as a 180 degree V12 as two oposing cylinders shared the same crank throw.
 

revkev6

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I did forget to mention, on the OP's subject. you CAN get 180 degree cranks for chevy's. not cheap but they are available from several crankshaft manufacturers without having to get something one off made. not that it helps with the other just as insurmountable hurdles that such an endeavor would have.
 
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