Steps to scratch build a VW

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

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  1. Aug 29, 2019 #461

    dmar836

    dmar836

    dmar836

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    We know the Formula V guys ran oil coolers. Some had room to run them across the top of the engine. You won't. Blueberry(#77) had a fairly elaborate pressure plenum setup. Ed could comment on that stuff.
    Not too much oil volume in a VW but the point where more oil flow is actually necessary vs. just a good idea hasn't really been proven to me. Not that it isn't beneficial but at just what point is it necessary. There are buses with over 100,000 miles on them without the HVX mods. I'll likely do the HVX mods as it "can't hurt" as long as the pressure is bumped up. Increasing flow without extra volume could create some issues but I don't want an add on pan, sump, etc. I read somewhere that we should "port" oil return holes to the bottom of the engine to facilitate unrestricted oil return.
     
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  2. Aug 29, 2019 #462

    Vigilant1

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    HVX Mods: Part 1-- Why and What/How:
    Why: A very thorough explanation (history, problems seen, etc) in Bob Hoover's own words, with diagrams, is here: https://bobhooversblog.blogspot.com/2007/05/hvx-mods.html
    A snippet, for those who just want the short version:
    Worth doing? Here's what Hoover wrote:
    The modifications improve lubrication to the left-side valve train and also the increased oil flow to the heads improves cooling of the heads (good for all VW aero engines, but especially important as the HP goes up)
    What/How:
    The various modifications to the case, lifters, rocker arms are at Bob Hoover's site, above.
    Pops has written some very good info on how to do the modifications in several posts, here's a recent one: https://www.homebuiltairplanes.com/forums/threads/bob-hoovers-hvx-vw-engine-mods.31359/
    Pops gives a good trick for grinding the grooves in the lifters using a cut-down stock grinding wheel.

    Here's another link to a slightly different presentation by Hoover, some different illustrations, and a follow-on explanation of some of the case modifications: http://bobhooversblog.blogspot.com/...-max=2007-06-01T00:00:00-07:00&max-results=10
     
    Last edited: Aug 29, 2019
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  3. Aug 29, 2019 #463

    Little Scrapper

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    Looking forward to reading about this tonight.
     
  4. Aug 29, 2019 #464

    Vigilant1

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    Here's the excellent video Little Scrapper posted previously on this thread showing the HVX modifications to the case:
     
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  5. Aug 29, 2019 #465

    fly2kads

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    I noticed recently that CB Performance has included an oil groove in their newly retooled rocker arms:
    https://www.cbperformance.com/product-p/1686.htm
    So that is now a bolt-on mod, should one choose to do so.
     
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  6. Aug 29, 2019 #466

    Vigilant1

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    Related lubrication topics:
    - Best oil pump? 21mm, 28mm, 30mm, dual stage with scavenge ability.
    - Use of oil box attached to the carb to help prevent carb ice and to significantly cool the oil. Less impact on performance than heating the incoming induction air, no need to remember to turn it on, reduces oil temps. Pops built one, there are posts and pictures here on HBA.
    - Full filtration (if so--disposable spin-on filter or use heavy-duty case with replacable element?), improved in-engine filtration with added mini-sump? Use stock VW oil screen?
    - Oil cooler: Brand and mounting.
     
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  7. Aug 29, 2019 #467

    dmar836

    dmar836

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    Wondering if Wittman's copper coil cooler is similar to the oil box. His carb was on top so was likely kept warm. I have a cooler, maybe a Lycoming, that was given to me. Thought I might use it in conjunction with a plenum. There was a formula somewhere, maybe in Bingelis' books, on how to estimate the size of the inlet holes in a nose bowl to cool based on HP.
    Dave
     
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  8. Aug 29, 2019 #468

    Pops

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    If you are OK with the right head, (#3 and #4) getting oil 1/8 th of the time as ( # 1 and #2) head with the reduced lube and cooling of the head, don't do the extra work. If you have any head problems chances are it will be on the right head. And most of those problems will be caused by high temps. On the 1500cc engine VW even reduced the timing on #3 cylinder at the distributor. After that they moved the exhaust of the oil cooler outside of the fan housing. Before the exhaust hot air from the oil cooler was up stream of the #3 cylinder, called the Dog House fan housing.
    VW did the mods on the type 4 engine.
     
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  9. Aug 29, 2019 #469

    Pops

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    My engine had more power and much smoother running with the hot oil box. The incoming cooler air coming over the intakes at the top of the engine was causing the charge to condense into droplets and making the cylinders run lean and rich as all the droplet ran in the cylinder at one time.
    The 20 deg drop in the oil temps was just a side benefit.
     
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  10. Aug 29, 2019 #470

    Little Scrapper

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    Working on finding out. I'm just over an hour from Oshkosh and I'm trying to figure out how I can get permission to uncover Steve's little flyer.
     
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  11. Aug 29, 2019 #471

    Pops

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    Without the case mods you still have the reduced oil flow to the rocker arms compared to the other side of the engine.
     
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  12. Aug 30, 2019 #472

    blane.c

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  13. Aug 30, 2019 #473

    Raceair

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    I called my baffles racing 'boxes'...I built two sets, then Jim Vliet built another set after me. On the Sonerai.net site I describe it in more detail....ED
     
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  14. Aug 30, 2019 #474

    karmarepair

    karmarepair

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    The Hoover mods might have prevented the problems with the lifter bores, but not the #3. Here are some ideas:

    1. Something, something hard, went through the engine. Like spalled "chunkies" off the lifter or cam faces or the edge of the cam lobes. Which is why I like full flowing the case and a remote filter.
    2. #3 main was improperly fitted - too little initial clearance.
    3. The lifter bores are a puzzle to me. If it wasn't #1, then perhaps the springs were far too heavy,and/or the cam was too aggressive and/or the valve train wasn't very well set up, so that the rockers were side-loading the lifters?
     
  15. Aug 30, 2019 #475

    karmarepair

    karmarepair

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    http://www.sonerai.net/articles/eds-essays-racing-engine-baffles.pdf . Ed's (Raceair) article.

    The baffles need to extend out to force air through the heads near the exhaust port, assuming your heads have air passages around the exhaust port.

    http://www.n56ml.com/n891jf/vw/ for some comparison of heads by Mark Langford, who is mainly a Corvair guy, but has built and flown VWs as well. The MOFOCO castings look nice, but at least the set in Mark's pictures has almost no air passages through the heads. Mark's trouble with the Chinese 043 heads was not due to the castings themselves, but due to the "port and polish" vendor cutting away the boss around the exhaust valve guides for "better flow".

    The article Mark refers to that compares 18 heads. http://www.cfiamerica.com/images/pdf/Hot_Vws_Type1_Heads.pdf
    Original German rebuilt by someone reputable, or Chinese 043 clones CAREFULLY INSPECTED are the way I would go, me. Stock springs, bolt together rockers modified per Bob Hoover, stock valves, clamp on pressed steel valve covers.
     
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  16. Aug 30, 2019 #476

    karmarepair

    karmarepair

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    I ruined a junk case trying to do that drilling. I'm glad they are willing to do my next case for me, even if I have to ship it (well, at least half of it) to Spokane. The other mods are easy.
     
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  17. Aug 30, 2019 #477

    Pops

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    Bob Hoover has a measurement for drilling the passage in the case as 8.872" or 8 7/8" long. I mark my long drill bit with several wraps of tape and I stop about an 1/8" short. Then drill the passage down from the cam bearing saddle and both holes should just touch. Then finish both drilling . Have drilled 3 cases with no problems. To me grinding the grove in the rocker arms is the hardest part of the mods. But now it look like you can buy new rocker arms already grooved from CB Performance .
     
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  18. Aug 30, 2019 #478

    Mcmark

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    Camshaft spalling is and has been a problem with VW engines. A lot of the cause is them removing the zinc from the oils. This is more pronounced in high performance applications but the cams and lifters are all susceptible to this failure. There are zinc additives that I always added to the race motor, and a good friend/mechanic has been using synthetic with good results.
     
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  19. Aug 30, 2019 #479

    Vigilant1

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    Just be sure to avoid the 100% synthetic oils if using 100LL fuel.
    Luckily, there are still some oils available with enough zinc to keep these flat tappet engines happy.
     
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  20. Aug 30, 2019 #480

    Little Scrapper

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    So let's take a break here and write down what when wrong, why it went wrong and what you would do differently of you did it again. Anything that comes out of that conversation would be all upside.
     
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