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    Thread: crank feels tight after my rebuild

    1. Banned
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      05-26-2007 09:47 AM #1
      on my vr6 rebuild

      I did the following

      honed the block

      new rings

      new rod bearing set

      hears the story

      my vr was once supecharged and when taking out 3 of my pistons they had cracked skirts. so at my job i had a few used pistons and i tossed the new rings on and put it in there

      everytime i put a piston in i would turn the engine around and it would spin fine

      but it kept getting tighter and tighter as i went to the next and next

      on the 6th and final piston i droped it in torqued the cap and now the motor has locked up.. after takeing the piston out checking everything i gave up and threw a rod cap on there that i had around

      so the motor turns now. but it feels tight in my opion

      so my question is.. does a vr6 BRAND NEW rebuild have tight tolerneces? i can turn it with the 27 on the crank but u have to plant you feet almost but once i get it rotating with the wrench i can keep it spining..

      in you honest opion am i just nerverous or would you have checked by a machine shop?

      thank you ryan


    2. 05-26-2007 09:53 AM #2
      Check all the cylinder bores for straightness? It would be cheap insurance at this point to have a shop mic it all around and make sure everything is in spec.

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      05-26-2007 09:58 AM #3
      no actually did not do this..

      i think tuesday im going to drop it off at a machine shop because i dont feel like its right ..


    4. Member Slayer's Avatar
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      05-26-2007 11:48 AM #4
      did you bring it to a machine shop at all? it may need the crank trued and the block line bored.. it sounds like something is binding up. how about the caps? are they in the right places? they should be numbered
      Check out my Garage build thread 2008.5 GTI 2.0 TSI 6MT / APR K04 V3.1, APR IC, CTS 3" turbo back, Carbonio full intake, GFB DV+, BSH TB pipe, SB Stg2 Endurance clutch, BSH mounts, DG Shortshifter, FFM bracket bushings, Forge big knob, Koni coils, Coolingmist CMGS Meth injection, USRT spacer (DO3 & Snow 100 nozzles), 19" Miro stp3's, Centric rotors, Stoptech pads and TyrolSport bushings

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      05-26-2007 03:57 PM #5
      Quote, originally posted by 1 Low Coupe »
      no actually did not do this..

      i think tuesday im going to drop it off at a machine shop because i dont feel like its right ..

      good idea ryan


    6. Geriatric Member need_a_VR6's Avatar
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      05-26-2007 04:50 PM #6
      Don't just throw a rod cap on, it has to match the rod. Either get that rod resized with that cap, or get a rod and matching cap to try. At the very least you should be plastigauging each rod as you install and checking for proper clearance.
      -Paul
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    7. Member hotrados's Avatar
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      05-26-2007 05:17 PM #7
      did you even mic the cylinder walls before and after you honed them? did you mic all the pistons? throwing in pistons you had laying around the shop probably wasnt the best idea, i mean if theyre just laying around, theres probably a good reason why they are laying around...and for god sakes learn how to spell man

    8. 05-26-2007 06:11 PM #8
      Quote, originally posted by 1 Low Coupe »

      so my question is.. does a vr6 BRAND NEW rebuild have tight tolerneces?

      New rings and honing the cylinders does not make you engine BRAND NEW.


    9. Global Moderator King's Avatar
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      05-26-2007 06:58 PM #9
      Quote, originally posted by 1 Low Coupe »

      i think tuesday im going to drop it off at a machine shop because i dont feel like its right ..


      Unless you're planning to kill another engine, do yourself a favour and let a professional assemble the block.


    10. 05-30-2007 06:54 AM #10
      Quote, originally posted by Mr King »


      Unless you're planning to kill another engine, do yourself a favour and let a professional assemble the block.

      Maybe he and Haris should take a class in precise measurement tools and engine assembly


    11. Geriatric Member need_a_VR6's Avatar
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      05-30-2007 08:00 AM #11
      Just a trip to Napa to bother the counter guy would go a long way here.
      -Paul
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    12. Member mk2vrooom's Avatar
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      05-30-2007 11:58 AM #12
      Quote, originally posted by need_a_VR6 »
      Just a trip to Napa to bother the counter guy would go a long way here.

      ...haha so true...


    13. Member Zupek's Avatar
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      05-30-2007 12:25 PM #13
      just to clarify, you have to plant your feet and put that much behind it with the head off? If so there is something binding up. You did oil everything while you were assembling, right?
      My 24v 3.1L Syncro Mk3 build here

    14. Member Technik Motorsport's Avatar
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      05-30-2007 02:24 PM #14
      if your swapping rod caps, there in lies your problem.
      They are matched to the rod it was line bored on from the factory or machine shop.

      You can not under any circumstances mix and match rod or main caps.


    15. 05-31-2007 02:04 AM #15
      Quote, originally posted by Technik Motorsport »
      if your swapping rod caps, there in lies your problem.
      They are matched to the rod it was line bored on from the factory or machine shop.

      You can not under any circumstances mix and match rod or main caps.

      but what if he didn't number them or keep them bolted to the rods?

      now what is he supposed to do?


    16. Former Advertiser Eric@tuninggruppe's Avatar
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      05-31-2007 02:14 AM #16
      Quote, originally posted by Technik Motorsport »
      if your swapping rod caps, there in lies your problem.
      They are matched to the rod it was line bored on from the factory or machine shop.

      You can not under any circumstances mix and match rod or main caps.

      Yeah it makes me nervous to think internals came out and just got all mixed up. For all we know everything went back in dry. No oil on walls. No oil or assembly lube on bearings. A dry motor wont spin or will barely spin with no lube. That was my first thought. If caps are mixed up thats not gonna help either.


    17. 05-31-2007 07:51 AM #17
      Quote, originally posted by brilliantyellowg60 »

      but what if he didn't number them or keep them bolted to the rods?

      now what is he supposed to do?


      Either find out a way to match things up using machinist's tools or Plastigage, have everything rebored and use oversize bearings or throw it all in the trash.


    18. 05-31-2007 07:56 AM #18
      Quote, originally posted by Eric@tuninggruppe »

      Yeah it makes me nervous to think internals came out and just got all mixed up. For all we know everything went back in dry. No oil on walls. No oil or assembly lube on bearings. A dry motor wont spin or will barely spin with no lube. That was my first thought. If caps are mixed up thats not gonna help either.

      here he is "honing the block" without any lubrication

      (check the engine stand, notice nothing dripping on it, and nothing splattered on his shirt or pants)


    19. Geriatric Member need_a_VR6's Avatar
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      05-31-2007 08:39 AM #19
      Quote, originally posted by VgRt6 »
      have everything rebored and use oversize bearings or throw it all in the trash.

      Pulling all the rods would be a pain but getting the caps milled and then the rods resized wouldnt' be bad at all money wise.

      -Paul
      1995 GTI VR6 - Retired - 12.90@106 R32 power - 12.833@106 12v power
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    20. Member Technik Motorsport's Avatar
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      05-31-2007 08:44 AM #20
      Quote, originally posted by brilliantyellowg60 »

      but what if he didn't number them or keep them bolted to the rods?

      now what is he supposed to do?

      Bring the rods back to a machine shop.

      Assembling it or playing roulette with caps is a recipe for disaster.
      Wiping out a crank after a few mies would be much less fun.

      So I have to ask,
      Did we bolt the head on after verifying the bottom end was binding?


    21. Global Moderator King's Avatar
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      05-31-2007 08:47 AM #21
      Quote, originally posted by Technik Motorsport »

      Assembling it or playing roulette with caps is a recipe for disaster.
      Wiping out a crank after a few mies would be much less fun.


      Thats Ryans way. He laughs at danger.


    22. Member Technik Motorsport's Avatar
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      05-31-2007 08:48 AM #22
      Shakes head and walks away.

    23. Member Technik Motorsport's Avatar
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      05-31-2007 08:59 AM #23
      Quote, originally posted by brilliantyellowg60 »

      here he is "honing the block" without any lubrication

      (check the engine stand, notice nothing dripping on it, and nothing splattered on his shirt or pants)

      Hes just de-glazing.
      Honing is almost the final step of resizing and is done at a machine shop.

      You don't need lube to deglaze depending on what stones you use.

      To clear up the dry cyl walls during assembly, there is nothing wrong with that.
      It actually helps seat rings.

      You cannot swap rod or main caps, you will grenade your bottom end if it spins at all. Metal transfer begins almost immediately.

      Remember, these journals are designed to run on a film of oil after the pump starts spinning, not on the bearing shell itself.
      That shell is there to keep the clearance proper to hold the film of pressurized oil. This is why you see pressure drops with a worn bearing or crank journal.

      Plastigauge wont always tell you if you have a cap swapped because typically the lack of clearance isn't on the bearing shells main surface but rather the pinch point.

      The bottom line is, if it doesn't turn over by hand without the head on, it needs to be torn down.

      Attention to detail should be addressed when assembling a rotating assembly. Check Check and recheck.
      If you are unsure, don't waste your time.


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