1970 LT1 Crank Pulley Bolts - NCRS Discussion Boards

1970 LT1 Crank Pulley Bolts

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  • James H.
    Expired
    • February 2, 2019
    • 75

    1970 LT1 Crank Pulley Bolts

    Can anyone tell me the proper finish (color) of the three bolts that hold the crank pulley to the harmonic balancer as well as the finishes on the center thick washer, bolt and tooth washer that bolts to the end of the crank and through the center of the crank pulley?

    I have the TI Manual for 1970, but I don;t seen a picture or detail about it there. Best would be a picture if anyone has one?

    Thanks in Advance

    Jim
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43221

    #2
    Re: 1970 LT1 Crank Pulley Bolts

    Originally posted by James Hubbard (65614)
    Can anyone tell me the proper finish (color) of the three bolts that hold the crank pulley to the harmonic balancer as well as the finishes on the center thick washer, bolt and tooth washer that bolts to the end of the crank and through the center of the crank pulley?

    I have the TI Manual for 1970, but I don;t seen a picture or detail about it there. Best would be a picture if anyone has one?

    Thanks in Advance

    Jim

    Jim------


    The balancer pulley bolts were supposed to be 3/8-24 X 5/8", GM-280M material (3 lines), zinc finish, and non-indented (trimmed) head. However, I would not be surprised if at least some were built using the base engine bolts. These were 3/8-24 X 3/4", GM 280M, phosphate finish, and non-indented head.

    I believe the pulley bolt washers were zinc plated split lock washers but if the standard engine bolts were used, probably phosphate or natural finish.

    The crankshaft bolt was 7/16-20 X 2-1/4", GM 300M material (6 lines), phosphate finish, and non-indented head.

    The lockwasher was an external tooth lockwasher, natural finish

    The large flat washer was natural finish
    In Appreciation of John Hinckley

    Comment

    • Ron G.
      Very Frequent User
      • December 1, 1984
      • 865

      #3
      "SOLID LIFTERS MATTER"

      Comment

      • Ron G.
        Very Frequent User
        • December 1, 1984
        • 865

        #4
        "SOLID LIFTERS MATTER"

        Comment

        • Terry M.
          Beyond Control Poster
          • September 30, 1980
          • 15601

          #5
          Re: 1970 LT1 Crank Pulley Bolts

          Ron
          I believe the front of the damper was covered, or somehow shielded from paint so that any pulley(s) added later had a flat surface to contact. No paint drips to throw pulley(s)s out of true.
          Terry

          Comment

          • Joe L.
            Beyond Control Poster
            • February 1, 1988
            • 43221

            #6
            Re: 1970 LT1 Crank Pulley Bolts

            Originally posted by Ron Goduti (8076)
            James,

            I should’ve mentioned this in my prior thread. Although the bolts were plated black oxide or black phosphate they received orange engine paint as the harmonic balance was attached when the engine was painted.

            Ron------


            The harmonic balancer was installed at the engine plants. However, the pulley, pulley bolts and crankshaft center bolt was installed at St. Louis.
            In Appreciation of John Hinckley

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43221

              #7
              Re: 1970 LT1 Crank Pulley Bolts

              Originally posted by Terry McManmon (3966)
              Ron
              I believe the front of the damper was covered, or somehow shielded from paint so that any pulley(s) added later had a flat surface to contact. No paint drips to throw pulley(s)s out of true.

              Terry------


              Yes, but only the slightly raised portion of the balancer hub's face where the pulley seats was masked off or otherwise protected from paint. The rest of the exposed portion of the balancer was painted with the engine.
              In Appreciation of John Hinckley

              Comment

              • Ron G.
                Very Frequent User
                • December 1, 1984
                • 865

                #8
                Re: 1970 LT1 Crank Pulley Bolts

                Joe,

                My bad. I was thinking of the harmonic balancer and not the pulley that attaches to it.

                - Ron
                "SOLID LIFTERS MATTER"

                Comment

                • Joe L.
                  Beyond Control Poster
                  • February 1, 1988
                  • 43221

                  #9
                  Re: 1970 LT1 Crank Pulley Bolts

                  All------


                  I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?
                  In Appreciation of John Hinckley

                  Comment

                  • Ron G.
                    Very Frequent User
                    • December 1, 1984
                    • 865

                    #10
                    "SOLID LIFTERS MATTER"

                    Comment

                    • Joe L.
                      Beyond Control Poster
                      • February 1, 1988
                      • 43221

                      #11
                      Re: 1970 LT1 Crank Pulley Bolts

                      Originally posted by Ron Goduti (8076)
                      Joe,

                      phosphate. I’m not sure about the front of the harmonic balancer, but if Joe and Terry says that it was masked then I believe it. However, I know that the backside of the harmonic balancer did not receive any paint.

                      Ron------


                      ...and, just to confirm, you're referring to the 3 balancer pulley bolts, not the center crankshaft bolt? The center crankshaft bolt was definitely phosphate.

                      If the pulley bolts are phosphate that means that the base engine bolts, GM #9423959, were used rather than the bolts scheduled for the LT-1 application, GM #181629. The 9423959 were phosphate; the 181629 were zinc. Both should be GM 280M material (3 lines).

                      It would be nice to hear from some others to try to determine if it was all LT-1's that got the base engine bolts or just some.
                      In Appreciation of John Hinckley

                      Comment

                      • Terry M.
                        Beyond Control Poster
                        • September 30, 1980
                        • 15601

                        #12
                        Re: 1970 LT1 Crank Pulley Bolts

                        Originally posted by Joe Lucia (12484)
                        All------


                        I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?
                        1970 LT1 s/n 14,544

                        1970 LT1 sn 14544.jpg
                        Terry

                        Comment

                        • James H.
                          Expired
                          • February 2, 2019
                          • 75

                          #13
                          Re: 1970 LT1 Crank Pulley Bolts

                          Ron,

                          Are you saying that the center bolt and large washer and the 3 bolts that screw into the harmonic balancer, were screwed into the balancer, and the end of the crankshaft when the engine was painted orange, then removed to put on the black colored crank pulley, leaving all 4 bolts and washers painted orange?

                          Thanks

                          Jim

                          Comment

                          • Joe L.
                            Beyond Control Poster
                            • February 1, 1988
                            • 43221

                            #14
                            Re: 1970 LT1 Crank Pulley Bolts

                            Originally posted by Terry McManmon (3966)
                            1970 LT1 s/n 14,544

                            [ATTACH=CONFIG]100856[/ATTACH]

                            Terry-------


                            Here it appears that the pulley bolts were phosphate finished (now deteriorated to rust). I've always kind of figured that the LT-1 engines would not have received the zinc plated pulley bolts that the AIM specified (GM #181239). The line workers probably "simplified things" by using the standard engine bolt, GM #9423959, for all applications.

                            The big surprise here is the center bolt. The bolt specified for all 69+ small blocks was GM #9428643. This is a phosphate-finished bolt. The bolt I see is a zinc plated bolt. A zinc plated bolt was used for 1963-68 SHP small blocks but that bolt had a safety wire hole through the head. So, I don't know what this bolt is.
                            In Appreciation of John Hinckley

                            Comment

                            • Terry M.
                              Beyond Control Poster
                              • September 30, 1980
                              • 15601

                              #15
                              Re: 1970 LT1 Crank Pulley Bolts

                              Originally posted by Joe Lucia (12484)
                              All------


                              I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?
                              Not to confuse the issue, but this is a 1972 base motor with 10K miles. It happened to be available to photograph.

                              1972 Base 10Kmi.jpg
                              Terry

                              Comment

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