Post Conversion - Crank Rotation Tight

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

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  1. Jul 4, 2019 #81

    BBerson

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  2. Jul 4, 2019 #82

    Pops

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    I torque at the VW book pattern but just 5 lbs steps at a time and switch sides on each step on the cylinder/head studs.
     
  3. Jul 5, 2019 #83

    lakeracer69

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    looks like Gasgacinch is readily available. I just looked.
     
  4. Jul 5, 2019 #84

    Tuneturkey

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    Where can the stuff be purchased? Hopefully it is easier to work then Permatex, which seems to setup to fast.
     
  5. Jul 5, 2019 #85

    Hot Wings

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  6. Jul 5, 2019 #86

    TFF

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    Looks like rubber melted in toluene from
    The MSDS. Good old fashioned type of sealant.
     
  7. Jul 5, 2019 #87

    Tuneturkey

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    TFF - No, only the 6 M12 bolts in the crank and CAM tests.

    On an earlier post, there was a discussion about "hand scraping" regarding the roundness of the CAM saddles in the case. Please explain what that is and how it is done.

    I did some checking for CAM bearings on line, and came to the realization that all CAMS have std. size journals and std. size bearings, and the case has std size saddles. I don't see how align boring the cam saddles can work if you can't by oversize bearings. Am I correct on this?

    As a general observation based on the wear ( circular scratches) on the bearings, I picture the case in my mind (Xray image), Crank at the top, CAM at the bottom with the two gears meshed with Centerlines lining up vertically. The 1/2 VW has a short CAM shaft, with the back half cut off, so there are only 2 bearings. Strangly, The wear on the prop end bearing (first case assembly that started this topic) was pretty even across the face of the bearing, whereas the wear on the back bearing was south southwest 195-200 deg (CW from 0 deg.), visualizing from the prop end, case upright.
    If the CAM timing gear is too big, it seems to me that the wear on the aft bearing would be at 0 deg., or due north. The over size CAM gear on one end would force that end of the CAM down, pivoting on the first bearing and causing the AFT end of the CAM up, wearing the top of the 2nd bearing, but that is not what happened. On that iteration of opening and closing of the case, all bolts had been torqued, The crank turned with resistance, using a 24" long psudo prop bolted to the prop hub. From this finding, I accepted the conclusion that the case was warped based on the wear pattern on the bearings.
    However, upon opening the case again, I found adjusting the three CAM bearings and seating them on the dowels, eased the tension in the crank and it rotated with 80% less effort. Following this, the case was closed up, all bolts torqued, and the tightness in the Crank rotation was less, but still more then with the case open. Now, did I do the torquing sequence the same both times, probably the same torque levels, but the exact same sequence, bolt to bolt, no! All y'alls comments about case distortion when torquing the case bolts leads me to believe that all may not be lost!
    Lesson #155 in this project - The magnesium case is not as rigid as steel or cast iron, and will deform in the torquing process. It was a big letdown, when I went from no resistance on crank rotation (open case) to tight when torqued. Bummer!!!
    New finding: with the Crank bearings fully seated, rotation of the crank does cause the cam to lift up maybe a 16th of an inch with corresponding roughness in the mesh of the teeth. I feel that this is some of the problem, particularlay with the CAM constrained it its bearings. So a new CAM is on order with a -2 radius gear, although I will discuss with the CAM vendor. Too bad I can't return the old cam, but $59 is not too bad. In addition, I ordered a new set of CAM bearings.

    In addition, I will secure a telescoping guage and check the CAM saddles for roundness.
    Johnc
     
  8. Jul 5, 2019 #88

    Hot Wings

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    You really don't want to know. :eek:
    It's a last resort kind of thing that went out of style with poured Babbitt bearings and splash oiling.

    The parting surface of the VW case tends to wear/crush when things don't get put together correctly, or overheated in service. When the case gets retorqued that clearance is 'removed' and you end up with an ovalized bore. Kind of like what is done on purpose when the big ends of a rod gets resized. The red oval is what I suspect your cam bore looks like. The black circle is the desired dimension. The cut will remove a small amount of metal from the top and bottom of the oval but a lot from the sides. cam.jpg
    " I found adjusting the three CAM bearings" From this I presume that this is a full case 1/2 VW along the lines of the "better half"? If so then the the standard VW cam boring tool will work just fine to clean thing up...... no scraping or complicated lathe setup required.
     
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  9. Jul 5, 2019 #89

    BBerson

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    What does a cam boring tool look like? Why can't it true a half VW? Or, why would a used engine have a tight bore?
     
    Last edited: Jul 5, 2019
  10. Jul 5, 2019 #90

    Hot Wings

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    Didn't think I'd find this, much less the first hit:



    Edit: I'm one of the ones that uses #30 on the 12mm nuts.
     
  11. Jul 5, 2019 #91

    BBerson

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    Thanks. But crank line boring requires oversize bearing inserts.
    What do they do with a worn out cam bore?
    He mentioned reaming just to true it from warpage. I suppose some sort of line honing might work also. It seems odd the cam bore could be tight unless an oversize cam is being fitted into a standard case bore.
     
  12. Jul 5, 2019 #92

    Hot Wings

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    There were at one time OS inserts for the cam. I had a case once that had been bored for the OS cam bearings. Had to toss it because I couldn't get bearings. The old 40 Hp cases could, and were, bored to take the standard cam inserts. They had straight aluminum bores with no bearings - same size cam journal. Most of these were factory rebuilds.

    Just so you know if you see one, the factory rebuilt cases had the original serial number milled out and a new one stamped. In today's world that might get you a visit from the suit boys wanting to talk and starting off with a Miranda advisory.

    Odd? For an iron block Chevy, yes. But VW's had a very different lineage. It's just part of their 'charm'.
     
  13. Jul 5, 2019 #93

    TFF

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    it will depend on how straight a case is when doing it. The parting surfaces have to be machined then the hole. Here is a Subaru done a little fancy.
     
  14. Jul 5, 2019 #94

    N8053H

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    My case had to be replaced because the cam was bored and there was not over size bearings in the size it was bored. I had all sorts of problems setting valve lash because of this. The cam was moving and caused erratic readings when checking valve lash. Oil pressure was also low.
     
  15. Jul 7, 2019 #95

    Winginitt

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    The thing about your problem is that there can be some misalignment, bore size incorrect, or both. When checking bearing clearances you MUST have a decent tool that is designed for the job. Don't rely on plastigage for anything other than a "feel good" if you have an engine where everything appears to be interacting properly. If, as in your case, there is a problem....then you need to be able to accurately check dimensions. Telescoping gages are handy and the Harbor Freight ones should work for most things....But they rely on the ability to use multiple measurements and feel. You have to get a feel in the bore with the telescoping gage, then mic the telescoping gage and get another feel...to produce a reading. When you are dealing with tolerances that are extremely close, there is plenty of room for inaccuracy.
    Inaccuracy means that you didn't actually find anything out...even if you think you did.
    Dial Bore Gages are extremely accurate direct reading instruments and can be used for larger bores with the interchangable anvils. Best to forget about trying to get accurate information unless you purchase the right tool for the job.
    https://www.amazon.com/Fowler-72-64...ocphy=9014176&hvtargid=pla-493153854403&psc=1
    If your crank spins freely, then it sounds like thats probably not part of the problem. If the cam binds, put it between two centers (in a lathe) and hand turn it with a dial indicator on each bearing surface. Thats the best way to insure its not bent. A machine shop could check it for you in just a few minutes. You can also try placing the end journals in V-blocks and turning it by hand. Since you mentioned that the gears have a gap sometimes and sometimes they don't, it sounds like a bend rather than a diametrical size probem.
    Do you have any other cases you could try the cam in? Or any other cam you could try ? Are the scratches only on one area of the bearing as opposed to completely 360 degrees?

    When "align boring" an engine the main bearing caps or in the VW the faces of each case half are "trued" flat by removing a minimal amount of metal with a milling machine. They can be subsequently "lapped" for flatness if desired. This closes down the diameter of the main bearing bore horizontally. Then the block is placed in a machine or jig that will allow either a boring bar or a large hone mounted on a shaft to pass thru all of the main bores and restore them to the original size....and all in line.....hence "line boring " which is really "align boring".
     
    Last edited: Jul 7, 2019
  16. Jul 8, 2019 #96

    Tuneturkey

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    Thanks for you lengthy reply:
    The case has been opened inspected and re-assembled going on 5 times. I've gotten good at it!
    Taking all comments from all responders seriously, The case has been inspected thoroughly and I have noticed some things that may be a problem, but identified by anyone.
    Yesterday, I decided to clean up the case of all sealant, clean all bearings and parts, and reassemble the case following a very careful sequence, based on the VW manual that I have been following.
    before closing the case I checked the mains to be sure they were fully seated on the dowels. One bearing had rotated 1-2 degrees and as I rotated the crank, the cam was lifting up about 1/16" or so at one point on the rotation. Checking the bearings, the #3 bearing was off the mark, so I rotated it until it seated. A re check of the cam showed it remained seated in the bearing thru 360 deg of rotation, no lifting. I rotated the crank and checked the gear lash and there is a slight click in the mesh of the gears. I also took my feeler gauge and check the end endplay of the cam at the thrust bearing and found it to be 0.003" which per the manual is ok. At this point, everything looked good, crank rotates smoothly, no obvious issues, so I applied the sealer sparingly, closed the case. After tapping the case with a rubber mallet to close it the lase few mm's, checked the crank again and still free. Torquing sequence was :
    1. Snug all bolts up to pull case halves together with a ratchet.
    2. Torque the two cam plug studs up to 14# (Checked crank and some tightness beginning)
    3. Starting in the center, torque the 6 main bearing nuts to 15# in steps of 5# per cycle. ( checked crank tightness at each step, and crank continued to tighten) at 25# crank was difficult to turn by hand.
    4. Torqued all remaining bolts to 14# is several steps.
    Crank hard to turn by hand, but easier with 2 ft long pseudo prop bolted to prop hub.
    Not good. Per previous comments, crank should turn by hand with no binding are tightness.

    Next step was to remove all bolts and separate the case halfs.
    -crank bearings were still in the sam positions on the marks. Nothing noted on the CAM position, other then the lube on the middle bearing ( this is a 1/2VW full case, at the #3 main bearing) appeared grey in color, to me indicating some heavy metal rubbing. With the CAM out, there was some heaving rubbing on the bearing on the right half at the 200 deg clockwise rotation, 0 deg beginning as case joint with case vertical. the other bearing closer to the gear was clean, no discoloration. (photo of the bearings is attached to a previous post).
    based on having watched numerous videos on align boring the crank and some on boring the cam, it was pointed out several time that the middle bearing takes a beating and either gets out of round, or moves out of alignment.
    Earlier on, Pops recommended I torque the case to full torque with only the crank in place, checking for tightness. Result was a free turning crank.
    The same routine was performed with only the cam in place, and at full torque, the cam was locked and wouldn't turn.

    At this point, I am concluding that in fact the CAM bearing saddle is deformed in some way, causing sever binding under tull torque conditions.
    My intention at this point is to locate a proper measuring tool and check for deformity on the Cam bearing saddle, then find some repair shop that has the tool bar and cutter, to reshape the cam saddle bore, hopefully removing minimum metal so that the std bearing will still fit. At this point, a source for oversize bearings has not been found.

    Any comments you may have will be appreciated.
    Johnc
     
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  17. Jul 8, 2019 #97

    fly2kads

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    Sounds like you're on the right track. Hopefully you can find a shop there in south Louisiana that knows air-cooled VWs and can do the work for you. If you need to search farther afield, I hear good things about Smith Foreign Auto in Houston. I use Automotive Machine & Supply here in the DFW area, and they have been great.
     
  18. Jul 8, 2019 #98

    proppastie

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    So how does a case end up warped at the cam shaft? Maybe bent cam? V-blocks and dial indicator .
     
  19. Jul 8, 2019 #99

    Kamcoman77

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    I would try and borrow a camshaft from someone and test the rotation with the cam only, case torqued. If same tightness, at least you can rule out a bent camshaft. Have you checked the thickness of the cam bearings to see if one was machined thicker than the others? Have you moved the non-thrust cam bearings from one journal to another to see if it made a difference?
     
  20. Jul 8, 2019 #100

    Hot Wings

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    Improper torque values or overheating.

    Having the nuts too loose lets things move around and the case wears due to the relative movement of the contact surfaces. It may only be hundredths of a millimeter, but that is all that is needed.

    Overheating lowers the strength of the alloy, sometimes to the point that the extra force on the fastener from the expansion actually crushes the metal* under load. Once cold the prevailing torque is less than specified and the wear begins - leading to even less prevailing clamping pressure. It's a self-compounding series.

    *The VW 12mm case seal nuts are the weak link. The 'plastic' used fails due to creep, which increases due to heat. Bad stuff then happens.
    Over heating is also why the thin wall of big bore cylinder sets are more prone to develop head leaks and 'require' re-torquing.
    Basic lesson - keep things cool.
     
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