Post Conversion - Crank Rotation Tight

Discussion in 'Half VW' started by Tuneturkey, May 31, 2019.

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  1. Jul 1, 2019 #61

    Tuneturkey

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    Last comment before moving on.
    We Aviation nuts take a 1600cc case, block off two cylinders, up the stroke and bore, add a carb to each cylinder to get 30-32hp out of it that shakes, rattles and rolls. wouldn't it be better to get a 1200cc case, up the bore on all four cylinders, with std stroke crank to get maybe 40hp, and a smoother running engine. Seems the smaller case would be lighter, and all the hubbub with cutting the crank, adding counterweights, etc could be eliminated.
    my 1/2VW, 1600cc full case with 69mm crank and two 92mm jugs will do maybe 30hp with dual carbs, but weight 85lbs, no electric start, no gen.
    Question: Is it possible to build a light weight, 1200cc, 4 cyl engine that will produce 40hp and weigh 85# or less?
    I am coming to the opinion that I am building a compromised, compromise at best with the 1/2VW!

    Probably should be a new topic, so just keep your comments short!
    Johnc
     
  2. Jul 1, 2019 #62

    BBerson

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    I have been trying to figure a way to make a 1600 VW very light with low power. I don't think the old 1200 case is any lighter. I figured a 120 pound VW might be possible with significant carving. Haven't figured how to hand carve weight off yet.
     
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  3. Jul 1, 2019 #63

    Pops

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    A VW long block ( no carb or intake manifold, no exhaust system and no mag or distributor, no prop hub). Bare engine , is 116 lbs. 1200cc, 1300 cc, 1500 cc, 1600cc, 1700 cc and 1835 cc, all are 116 lbs. I have weighted them all. The 1200cc has a little lighter case but thicker cylinders so its the same. I saw the top of the case above the 2 top mounting bolts. Make a 3/16" aluminum bottom oil plate instead of the about 5" round steel plate. Use an aluminum oil pump cover instead of the heavy steel cover ( with an oil output for full flow oil system). Aluminum intake Y at the flywheel end of the engine. Small 1/8" generator pad with a reed valve made into it for the crankcase vent. 1/8" cover for the fuel pump pad and distributor hole in the case.

    You can see where I cut the case on the top flywheel end in the picture.
    Also picture of the 1200cc, 40 HP engine. Sweet little engine.
     

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    Last edited: Jul 1, 2019
  4. Jul 1, 2019 #64

    BBerson

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    I meant 120 pounds with the ignition and carb, hub, etc. ready to fly. Yours was probably 135-140, I guess.
    The optimum would be 1600cc 40hp at 80 pounds. That's a typical airplane engine weight, two pounds per hp.
    I figure all the big parts need to be reduced in weight by 25%. I know the stock engine is overbuilt for 40hp because they get 80hp out of it, and I would be running it at a derated rpm of 2700 or something.
     
  5. Jul 2, 2019 #65

    Pops

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    My firewall forward weight is 141 lbs. That is everything to fly including the prop. Just unbolt the engine mount from the firewall and weigh. 1835 cc, 60 HP.
    There is different between engine weight and firewall forward weight. Prop & bolts and crush plate, engine mount, oil cooler and lines, Baffleing, etc , all add up quick.
    My SS exhaust and upper part of the SS intakes could be made from .035 instead of the .050 that I used, saved a few ounces in a couple other places. Maybe could have made it a total of about 138/139 lbs firewall forward weight.

    No way are you going to get a 1600cc VW engine with the ignition, carb, hub , ready to fly at 120 lbs.
    In a flywheel drive engine the complete flywheel end of the case has been cut off to save weight by a few people. That is all the round part that mates to the transaxle.
     
  6. Jul 2, 2019 #66

    Tuneturkey

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    Page 2:

    Going be recommendation from Pops to install only the cam at 10# torque to see if it turns, and repeat for the crank at 10#.
    The crank spins at 18# same as no torque.
    The CAM locks up tight at 10# and won't turn with a screw driver.

    CAM is standard for a 1600cc engine, although dish faced. Bearings are also VW stock for the 1600cc type 1. Cam bearings after test are scratched as it the cam journal is too big, or the bearings are too small for the shaft. The scratches appear to be about the same on both bearings. ( this is a 1/2VW with back half of cam cut off.

    Hate to hollar for help again, but ?
    Johnc
     
  7. Jul 2, 2019 #67

    BBerson

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    Do you have a micrometer and inside bore guage?
     
  8. Jul 2, 2019 #68

    Hot Wings

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    I'm giving 3-1 odds now that it's a deformed cam bearing saddle. :(

    Plastigauge and/or measure the center (now rear) cam bearing bore with no bearings. I keep forgetting that this is a !/2 VW so if the cam bore is ovaled the normal quickie boring bar isn't going to work if it's a cut case version. If it's a 'better half' then the standard bar will work.

    You could go to the old OLD school method of scraping to get it round again but that would be a not so fun job.
     
  9. Jul 3, 2019 #69

    Pops

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    Hand scraping. Brings back memory's. Working as a millwright, I had to hand scrap the bearing for a very large electric motor that ran the rolling mill for aluminum. Motor in one building and about a 4' dia drive shaft to the mill building. Rolls in the one mill weighed 200 ton. Armature maybe 15/20 ton. My job also included changing the 4 rolls in the mill.

    What is the serial number of the case? Located below the generator stand.
     
  10. Jul 3, 2019 #70

    Tuneturkey

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    I have a micrometer, but no inside bore gauge, although I can rent one.
    Case is an AS41, AK163732. Best I know is that it is 1600cc, 1972 Bug
     
  11. Jul 3, 2019 #71

    Hot Wings

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    Poor boy it! Cut a length of 1/8 inch welding rod and bend it into about 45 deg bend - to fit the vertical dimension of the bore. Polish the ends into a semicircle shape with some sand paper.

    Bend again so it just scrapes the bore in the vertical and measure the result. Twist 90 deg and see how tight it is. Rebend and remeasure as needed. It's not precise but takes no more time to do than it did for me to type this (I'm a slow typist). If you find a problem then you can go on to more precise measurements and/or a fix.

    Plastigauge should be a cheap quick way to tell too.
     
  12. Jul 3, 2019 #72

    proppastie

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  13. Jul 4, 2019 #73

    Tuneturkey

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    hey guys: Happy July 4th!
     
  14. Jul 4, 2019 #74

    Tuneturkey

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    hey guys: Happy July 4th!
    Current Status:
    1. Last test was to install only the crank, and torque 6, 12m bolts only to 10#, looking for free rotation. Passed, no change from open case.
    2. Repeat test with only CAM installed. CAM was locked tight, could not turn with screwdriver.
    3. Recommendation from several is to
     
  15. Jul 4, 2019 #75

    Tuneturkey

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    continuing - use a telescoping gauge and measure the cam journal bore with case torqued, or use plastigauge on Cam to measure fit.
    This has not been done yet, but soon.

    A close check of the cam, crank fit in the right half case shows some lifting of the CAM from its bearings. at that point in the cam gear rotation, the two gears are very tight. 180 degress from that point, there is a little slack in the fit of the teeth. Not much but some. per VW manual, that condition means cam gear radius is oversize. How much that condition influences the locked up condition at 10# torque on M12 bolts is the question.

    Case has been opened, and closed 5 times now, and things change each time. Very puzzling to say the least. The case is not as rigid as one would think, and evidently, the sequence for torquing the bolts makes a big difference. Also, with the crank in place with the CAM, torqued to 10#, the cam is free to rotate. Tight, but rotating. Without the Crank, the CAM locks up tight. ?????
     
  16. Jul 4, 2019 #76

    TFF

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    Are you torquing ALL the bolts every time? You don’t need to torque to final stretch but I would torque to 1/2 to 3/4 of final, every fastener. If the case does not seat, you will get different readings. Different torque patterns will give different readings. You have to assemble the case like it’s the last time every time.
     
  17. Jul 4, 2019 #77

    Hot Wings

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    And frustrating. This is one reason I'm so against some of the sealing methods used for the case halves. A bit of a story to clarify:

    Long ago there was a new miracle sealant that just came on the automotive market from the aviation world. It was this blue goop called Halomar. I was building a 911 engine at the time and thought this stuff would be a great sealant for the head/cam carrier seal. On a 911 there is a one piece casting that bolts on the top of the 3 individual heads/cylinders that the cams slide into. If it doesn't get torqued down perfectly flat the cams won't turn, just like your problem. I had already checked that everything was ready by bolting the top end together, with no sealant. When I did the 'final' install the cams were locked tight.

    Clean everything up and the cams turn just fine. Must be the Halomar not flowing out? Use less. Same result. Even let it set under half torque for 12 hours before final torquing. Same result. Gave up on the Halomar and went back to the old school, and proven, materials. Nasty job I'll never forget. The worn out mechanical fuel injection was even worse.....

    Lesson: Torquing has to be done in the same way, to the same values, every time or things don't go back in the same place. Unfortunately for us even if we follow this procedure the simple method of twisting a fastener to a specified value leaves a couple of parameters uncontrolled and the final clamping pressure can vary quite a bit. This works out OK if the joint is metal to metal and the engineer(s) did their job well. Put a layer of sealant (or a head gasket) into the mix? o_O:mad::(

    There is a reason we see torque and turn specifications and disposable torque to yield bolts.
     
  18. Jul 4, 2019 #78

    BBerson

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    It might be more precise to torque the halves without sealant, then put a vacuum and suck in some sealant.
     
  19. Jul 4, 2019 #79

    Hot Wings

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    My 911 experience was before we had anaerobic sealants, other then thread lockers. The nice thing about the newer sealers is that they allow the needed metal to metal contact, but still fill the small leak producing gaps. There is no squeeze out to fall off and plug oil passages and no time limits for assembly.

    My father told me he liked working on the Allsions so much better than the Merlins. He thought the idea of using gaskets was a lot better than lapping things to fit so they didn't leak. Sometimes I think he had things backward.
     
  20. Jul 4, 2019 #80

    TFF

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    Depends on who is paying for the lapping. Over on the biplane forum pretty much the same sealing discussion going on for Lycoming cases. Universal aviation concept.
     

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