Post Conversion - Crank Rotation Tight

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

Help Support HomeBuiltAirplanes Forum by donating:

  1. May 31, 2019 #1

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    Completed the conversion process. Engine is 69mm std. crank, 92mm case re-bore with new jugs; AS-41 type 1 case align bored, oversize bearings; new dished, std cam size zero; #4 thrust bearing moved to #3 position, #3 to #2 position (no split bearings installed); cut end of crank has end play shims. All oil gallery plugs removed, galleries cleaned, new plugs installed; new 26mm oil pump for dished cam, with external discharge cover, fittings, hoses to oil filter; Pre assembly lub of moving parts with white lithium greese, assembly lube and engine oil as prescribed in VW manual.
    Problem: Post closing case, crank turned by hand. Crank became increasing tight as torqueing of bolts proceeded. At full torque, crank turns single handed with short wood prop attached to prop hub, but with spark plugs removed.
    Currently: engine was filled with oil and hand rotated to force oil thru filter and into engine. oil pressure did not come up on gauge, although oil appeared in the clear plastic tube, case to gauge. ignition system is incomplete so engine has not been run.

    Need advice as to how to proceed:
    1. Complete ignition and hand prop to start, observing oil pres. and temp, and run in for several minutes until engine is fully lubricated.

    or
    2. Open case for inspection, check for issues.
    or do both 1 and 2?
     
  2. May 31, 2019 #2

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,045
    Likes Received:
    2,348
    Location:
    Port Townsend WA
    I would take the jugs off. The crankshaft must turn freely with no cylinders. With piston ring drag it's hard to tell.
    If the crank does not turn free then disassemble and check clearance with plastiguage.
     
    proppastie likes this.
  3. May 31, 2019 #3

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    6,385
    Likes Received:
    2,308
    Location:
    Rocky Mountains
    Sounds like a classic case of one of the dowel pin(s) denting the main bearing. The dowel pins are not centered and if you install one of the bearings backwards it results in exactly what you re describing. Easy to do. I've done it once or twice - even after a 100+ engines. Being aluminum the dowel punches the bearing pretty easily and you don't notice the increased pressure while torquing the nuts.

    The other possible problem is if the case was warped a bit and the crank bores line bored the crank will turn fine but the cam bores may be out of spec too. The test for this is to bolt the case together with just the cam bearings and cam installed. Then torque to specs and if you can't turn the cam with a screwdriver in the oil pump slot easily - the cam bore needs boring as well. Fortunately this generally doesn't require oversize cam bearings because the problem is generally limited to the center bearing which gets a bit smaller width-wise. A good VW shop will have a boring tool that takes about 10 minutes to fix this problem.
     
    proppastie, Pops and fly2kads like this.
  4. May 31, 2019 #4

    Pops

    Pops

    Pops

    Well-Known Member

    Joined:
    Jan 1, 2013
    Messages:
    7,132
    Likes Received:
    6,023
    Location:
    USA.

    Spot on. Been there and done that.
    I install the bearing in the case saddles and mark the bearing at the edge of the saddle with a sharp point felt black marker. That helps on locating the bearing in the saddle when installing in the case with the crank. That is a very easy mistake to do.
     
  5. Jun 1, 2019 #5

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    Thanks for the input!
    The bearings were marked as suggested on assembly and the bearings seated on the dowels.
    Just noted another detail. The tightness varies as the shaft is rotated, like something is out of round. The cam drive gear is original to the crank, but the cam gear is new. on initial assembly, the cam passed the rotation test on clockwise rotation, so it was assumed that the cam fit was ok. The new cam came with a standard size, or 0 size not -1 or +1, etc.
    Would it damage the engine to run it tight, if it will even start?
     
  6. Jun 1, 2019 #6

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    Thanks for the input!
    The bearings were marked as suggested on assembly and the bearings seated on the dowels.
    Just noted another detail. The tightness varies as the shaft is rotated, like something is out of round. The cam drive gear is original to the crank, but the cam gear is new. on initial assembly, the cam passed the rotation test on clockwise rotation, so it was assumed that the cam fit was ok. The new cam came with a standard size, or 0 size not -1 or +1, etc.
    Would it damage the engine to run it tight, if it will even start?
     
  7. Jun 1, 2019 #7

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    Thanks for the input!
    The bearings were marked as suggested on assembly and the bearings seated on the dowels.
    Just noted another detail. The tightness varies as the shaft is rotated, like something is out of round. The cam drive gear is original to the crank, but the cam gear is new. on initial assembly, the cam passed the rotation test on clockwise rotation, so it was assumed that the cam fit was ok. The new cam came with a standard size, or 0 size not -1 or +1, etc.
    Would it damage the engine to run it tight, if it will even start?
     
  8. Jun 1, 2019 #8

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    6,385
    Likes Received:
    2,308
    Location:
    Rocky Mountains
    I'd find the problem before trying to start it. If that means a complete tear down? ..... well, that's just life.

    A quick test for cam size is to set the cam and crank on one case half, I use a set of old main bearings on just the ends of the crank, and them rotate the crank in the direction that tends to lift the cam gear out of the block. If the cam is too tight the cam will lift out of the bearings. If it's too loose the only real problem is a slightly retarded cam timing. The old Formula V racers chose a -3 gear just for this reason.

    Back when I was building a lot of engines I had a couple of dozen cams, of various gear sizes so i could pick the right one.
     
    Pops likes this.
  9. Jun 2, 2019 #9

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    Thanks Hot Wings.
    yes, tear down is not fun, but necessary. I think that the problem is in the mesh of the cam gear and main gear, probably due to the center to center dimension change between the cam and crank. Crank rotation was smooth before cam install. More an issue to me is that the the tightness varies as the crank rotates reflecting something out of round. if that is the case, will the -2 or-3 cam gear help?
     
    Pops likes this.
  10. Jun 2, 2019 #10

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,640
    Likes Received:
    3,269
    Location:
    Memphis, TN
    The problem with split case engines is you can only test straight and round with the case torqued together. It can be warped when split but straight when torqued, like my Lycoming, or warped when tight. You are going to have to pull it apart and put the crank in and zip up the case and see; then pull that out and put the cam in by it’s self , close it up and spin it. You will probably see evidence once you spit it. It’s better to just do it all the way. It really only costs time.
     
    Pops likes this.
  11. Jun 2, 2019 #11

    delta

    delta

    delta

    Well-Known Member

    Joined:
    May 27, 2011
    Messages:
    1,923
    Likes Received:
    191
    Location:
    Brookside Utah
    I'd go with number 1... Complete ignition and hand prop to start, observing oil pres. and temp, and run in for several minutes until engine is fully lubricated.

    It doesn't sound that tight to me. If I was in a similar situation I'd run it. Add an oil filter if you don't already have one and inspect it after running for metal. I hope she loosens right up, doesn't make any metal, and makes a fine engine for you.
     
  12. Jun 2, 2019 #12

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,640
    Likes Received:
    3,269
    Location:
    Memphis, TN
    My Lycoming without cylinders is very easy to spin. One finger like stirring a drink. Can almost get one rotation if I “prop “ it. Every crank and cam I have ever put in an engine just glides. Only tight that you should feel on an assembled engine is ring drag and compression.

    For a short time I worked at a cylinder head machine shop. Overhead cam heads that warped would usually break the cam if you just surfaced them flat. The cam would be bowed and bind. We would bend the heads back just a little further than flat the other way on a jig that was not much more than an old cast iron cylinder head with milling parallel blocks at the end. Then we would cook it on a gas grill; high for 1/2 hour then low for three. Cam bearings would be flat, then you could surface it.

    I started sweating my Lycoming as the crank was pinching laying in the case. I had the crank turned and thought it was messed up. Once it was torqued, it was perfect. Just have to keep calm and understand the problem. If it is not explainable, stop until it is.
     
    BoKu likes this.
  13. Jun 2, 2019 #13

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    6,385
    Likes Received:
    2,308
    Location:
    Rocky Mountains
    It might help by masking the problem - if it's related to the cam gears. Is the resistance once per revolution or every 2 revolutions? If it's once it' most likely is a crank problem. I've seen reground cranks where the main journals are still nice and collinear but they got ground a little off center from the original. This makes the crank gear and pulley lands eccentric and you get a tight spot with every revolution as the crank gear passes it's top offset.

    If the cam gear is eccentric with the cam bearings - EASY to so with some of the bolt on aftermarket cam gears - then the tight spot only happens once every other revolution. If you are unlucky enough to have both gears misaligned with their respective bores.........you have a long day ahead of you to find the problem.

    I'm still betting on a dowel punched bearing. That too often is a cyclic thing as the dent passes the crank oil relief cut.
     
    Pops likes this.
  14. Jun 2, 2019 #14

    Pops

    Pops

    Pops

    Well-Known Member

    Joined:
    Jan 1, 2013
    Messages:
    7,132
    Likes Received:
    6,023
    Location:
    USA.

    I'm betting with you on a dowel punched bearing. Don't try starting the engine hoping the problem will go away. It will just get worse. Find the problem and make sure you fit it.

    I have watched a lot of the utube videos on building a VW engine. Some are a lot better than others but haven't see one video without doing something wrong or leaving something important out in the build. Haven't seen anyone torque the heads correctly. When going to the second torque pattern, just increase 5 lbs at a time on each side until you get to the torque setting.
     
    Last edited: Jun 2, 2019
  15. Jun 3, 2019 #15

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    More data: The least tight spot is with (facing prop hub) left piston at TDC, Tightness increases and remains thru 2 clockwise rotations (facing prop hub) back to TDC. So, the cycle of resistance takes 2 crank cycles and 1 cam gear cycle which tells me the Cam might be the culprit, due to being out of round, or being forced out of alignment by a bearing, or warped case. If thats the case, would running the engine allow the alum cam gear to wear, relieving the tightness. Seems that going to a -2 cam gear would allow the two gears to mesh more or less, without bottoming out and tightning up.
    Is there any other test I can do?
    Does the new data change opinions stated in replys above, Pops, Hot Wings, TFF, Delta?
    Thanks for the help Guys!!!
     
  16. Jun 3, 2019 #16

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    6,385
    Likes Received:
    2,308
    Location:
    Rocky Mountains
    It changes my bet a little bit. I'd have to have 3 to 1 odds now that it is the dowel pin. :D
    The only way to know what is causing this is to tear it down and measure/check till you find the problem(s).

    One of my very first rebuilds took 3 shots to get right. It was a 1200 CC 40 hp and it just wouldn't run. After the third opening I found an "extra" punch on the cam. Using that for an index put the cam about 30 degrees out of time. I didn't notice the problem because it was a new cam and "had to be right". Took a dial indicator and the specs for the cam timing to figure it out.

    Put a proper punch mark on the gear and that engine ran for the family for many years.
     
    akwrencher likes this.
  17. Jun 3, 2019 #17

    akwrencher

    akwrencher

    akwrencher

    Well-Known Member HBA Supporter

    Joined:
    Oct 16, 2012
    Messages:
    1,104
    Likes Received:
    393
    Location:
    Gustavus, AK
    Im going with the experienced guys, tear it down and check until you know for sure. There is a decent chance it won't even start, depending on the resistance. I've run into a couple instances where an assembled engine won't start due to extra resistance. One was a bug engine a freind rebuilt. We spent all night trying to start it, eventually he figured out it had the wrong oil pump. Ran fine after that. Anyway, you'll fly allot less puckered knowing your engine is correct and not hoping for the best;)

    Also did a full ruibuild on a John Deere genset a few years back and wouldn't start, was meticulous putting it together, and still had the injector timing 180 out. Had to do with using a home made timing tool and the way it was timed. Oops.....
     
  18. Jun 3, 2019 #18

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,640
    Likes Received:
    3,269
    Location:
    Memphis, TN
    My question is did you put it together or did you buy it together? If you did not do the initial work, I can see being skidish about taking it apart. If you did put it together, it should be straight tear in. It would be back together today if you pulled it apart this weekend and no flaws were found. This forum is great, but a diagnosis that can destroy your engine would be too big a bet for me. I would have to know, not guess. If you need to lap gears, it does not need to be in a running engine. Esentially you are saying it is OK to start an engine with either a spun bearing or bad timming gears off the bat. It will kill the engine if those are the problems. My engine was suppose to be easy. Bought the engine that was on my plane; I had bought the airplane separate. . Slap it on and fly was the goal. Valves were jammed for sitting a long time so it was not going to start. Took it a part and found stuff that would have been ok if I had not known but too wrong once I knew. That turned into a year of saving money to fix it. I could have forced it to run and destroyed the engine. It would been maybe a 200-300 engine at best. Things rarly get better, and they are always really bad once in the air.
     
    akwrencher and Pops like this.
  19. Jun 3, 2019 #19

    Pops

    Pops

    Pops

    Well-Known Member

    Joined:
    Jan 1, 2013
    Messages:
    7,132
    Likes Received:
    6,023
    Location:
    USA.
    I agree with TFF, just take it back apart and find the problem. Not guessing and hoping for the best. It will be worth it just for the education. At times we all had to learn the hard way but its not much work to take it apart and rebuilt it again. Then you will know for sure that its built right.
     
  20. Jun 3, 2019 #20

    Tuneturkey

    Tuneturkey

    Tuneturkey

    Well-Known Member HBA Supporter

    Joined:
    Dec 29, 2018
    Messages:
    53
    Likes Received:
    13
    Location:
    baton Rouge, LA 70816
    The engine is a put together by me. AS41 case used from Ebay. Crank from different engine; new cam, oil pump, valves, lifters, bearings throughout. Crank with counterweights and balanced by Scott Casler of Hummel engines. Cut the crank and head myself. used conversion plans from legal Eagle and others.

    last Question: all reference materials talk about TDC with the #1 cylinder at top when setting the timing. The Std VW numbering says the #1 is Rt side back next to flywheel ( facing the pulley end). On 1/2VW Only cyl. #2,4 remain (both on pulley end of the case), so when setting the timing, facing the pulley end, I raised the left piston (#4) to top and marked the crank at the case split. The rotor is in the normal ref. position, but the distr. is not marked. How do I know if this is the compression stroke, other then both valves closed?

    All right fellows!! You win.
    Next task is to open it up for a look see. I will surely post what I find, however, it may not be until after the 23rd.
    Thanks loads for all the input, advice and cautions! I am a firm believer in Forums, and have not gone wrong yet!
    Johnc
     

Share This Page

arrow_white