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building rb25 from ground up all perf. parts need help! small stuck at tdc!

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  • building rb25 from ground up all perf. parts need help! small stuck at tdc!

    hey guys, I've been on the forum for a while now finding info for my built rb25 swap into 1991 300zx.

    basically its a rb25det, had it disassembled cleaned, bored and honed for 87mm CP pistons.
    mods for bottom end is a custom oil pan to fin in my engine bay,
    ACL std main and rod bearings
    wide oilpump drive on cranks
    eagle rods
    cp 87mm .40 OB pistons
    Cosworth 1.5mm headgasket
    ARP main studs and head studs

    the head has been milled, port and polish with a 3 angle valvejob and supertech springs and Ti retainers.

    Basically I am assembling the motor, everything torqued, heads on.. torqued and when I go to spin the crank over with a wrench it goes nice and smooth except ONLY cylinder 1 when it gets to TDC its gets slightly stuck and requires a little bit to get it around, it docent sound like its" hitting" anything.

    The cams are NOT installed in the head yet, so all the valves are still up in the head.

    This is not normal right? it should be able to turn over nice and free the whole time?

    the rings were installed and the ring gaps set opposite of each other to spec.

    any help in where to look first? I torqued the rod ends to 45 pound a belove.
    also with this cosworth head gasket is it able to be un bolted from motor and reused?

    thanks you all for your time and help!
    this is a 2 year project and I want to get it running in a month or so since I finally have everything!
    -George
    91 300ZX 2+0
    Built RB25 in works, 2 year project hopefully completing this Spring!!
    Ttop to slicktop convertion/slammed and shaved everything/10 point cage/ Fully built RB25/Comp t68tbb/twin tial gates..ect ect

  • #2
    pulled the oil pump lastnight, and its still getting a little caught up, after work today I will attempt taking off the rod big end then re torquing to 43 pounds as per eagles instructions and hopefully that fixes it.. everything is freshly machined and all parts are new, there's no reason why I should be having any issues..
    91 300ZX 2+0
    Built RB25 in works, 2 year project hopefully completing this Spring!!
    Ttop to slicktop convertion/slammed and shaved everything/10 point cage/ Fully built RB25/Comp t68tbb/twin tial gates..ect ect

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    • #3
      hmm sounds sketchy, no you cannot reuse the head gasket once its been crushed, its crushed.

      Comment


      • #4
        Did you use the correct assembly lube, checked end caps are on the correct way (this does happen on RB engines and result is not nice) as this person had a similar problem -

        Tech / General Engine - Sealed Power assembly lube,crank hard to turn - I used THIS (http://www.summitracing.com/parts/SLP-55403B/) assembly lube which is green and very sticky/tacky on my main bearings and my crank seems like it wont turn when at full torque. If the caps are torqued at 25ftlbs,the crank is...


        Also I assume bottomend was balanced???
        RESPONSE MONSTER

        The most epic signature ever "epic".

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        • #5
          ok so I pulled the head of and the piston was actually coming in contact with the cosworth head gasket!

          So I pul head back on and used a lil screw driver to tap it over some..

          So now its touching on cyliners 2 and 4!

          The headgasket I bought is the correct 87mm bore and everything,
          I guess I will be callng back the company I got it from.

          This is ot normal for a head gasket to do this correct?
          Then its sitting on the head it can be mover a couple mm's in either way around the arp studs.

          This sucks!! More set backs!!!
          91 300ZX 2+0
          Built RB25 in works, 2 year project hopefully completing this Spring!!
          Ttop to slicktop convertion/slammed and shaved everything/10 point cage/ Fully built RB25/Comp t68tbb/twin tial gates..ect ect

          Comment

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