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Cam Gear Broken Teeth, aluminum gear 289

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  • Engine: Cam Gear Broken Teeth, aluminum gear 289

    Ok All. I have an Aluminum Cam Gear with broken Teeth. Some background so you can help diagnose this for me.

    My 289 is a 62 full flow block. I had it rebuilt short blocked 700 miles ago. So its pretty fresh. The crank was ground to 30 under.

    Recently my distributer sheared its drive pin. After some sleuthing I determined that something hard was jammed in my oil pump. I pulled the oil pan out and found broken aluminum cam teeth. Sigh. So I pulled the front end to get at the cam gear and found a lot of the teeth on the from of the gear broken off. See photos below.
    You can see on the gear on the drive side of the gear (back of gear towards car rear) that there is a lot of spalling on the teeth. On the front side of the gear, a number of teeth have been broken off.

    When I installed the cam gear and new crank gear, I did notice the fit was snug, with no appreciable backlash. But did not think much about it as the gear did slide on and cam seemed to rotate with no friction. Perhaps this was a mistake.

    So here are the questions.
    1. What could be causing this problem?
    2. If the problem is caused by a badly done line bore, what are my solutions? Can I install a fiber gear and hope that the clearance will open up?
    3. Any other suggestions to solve this problem?

    I really want to get my car on the road again and am not interested in pulling the engine and having it "fixed"

    Thanks in Advance. Click image for larger version

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  • #2
    I have heard lotsa stories over the decades of repro aluminum cam gears that were defective. Stories included high pitched whine, and gear teeth failure. Interesting to note, on yours, all broken teeth and tooth wear/contact patterns are on the front side of the gear. This would be cause to suspect the aluminum gear. With a fiber gear, you could do a comparison of fitment and teeth contact patterns.

    Other than a defective aluminum gear, about all that's left is a line bore that resulted in the crank and cam being too close. I'd explore the possibility of a defective gear first.

    Comment


    • #3
      Thanks Joe. The wear on the teeth on is kitty corner. Ie, wear on the one side of the tooth (that resulted in some being broken off), and on the back of the tooth on the other end of the gear tooth. Almost like the tooth angle was cut a fraction of degree off true contact angle. I intend to fit up a fiber gear and check for lash. But I am several days away from doing that.

      Comment


      • #4
        Crankshaft endplay in spec?

        Comment


        • #5
          Good point. I’ll check tomorrow. But why would that affect the teeth for cracking?

          Comment


          • #6
            Just part of the process of elimination.

            Comment


            • #7
              What about Cam Gear to Crank Gear alignment?
              In your picture, of the two mated, the Cam gear may not be seated all the way, but if that was it's running position the front Gear faces do not look flush.

              Are you saying the Main Bearing caps and Block were machined/line bored? ...WHY?
              I have never had a problem after Rebuilding an Original Factory Like bored Block. Sounds like the best way to ruin a Block.
              StudeRich
              Second Generation Stude Driver,
              Proud '54 Starliner Owner
              SDC Member Since 1967

              Comment


              • E. Davis
                E. Davis commented
                Editing a comment
                Also the alignment and the depth of the cam teeth to the crank gear are no where near matching. Might want to find a replacement for both that are not made in China.

            • #8
              That wear pattern sure looks like the gear teeth were hobbed at a slightly off angle. guess my aluminum cam gear will go in the "Trophy Cabinet". Luck Doofus

              Comment


              • #9
                You might want to shot some prussian blue onto the gears to check the contact pattern. I believe I read somewhere that such alloy gears had to be carefully run-in. Had this been done?
                sigpic

                Comment


                • #10
                  Originally posted by christophe View Post
                  You might want to shot some prussian blue onto the gears to check the contact pattern. I believe I read somewhere that such alloy gears had to be carefully run-in. Had this been done?
                  Sorry but that excuse is feeble. No reason to have to break a cam gear in, if it fits as it should. Sounds like a BS answer given by someone who maybe produced the gears. Unacceptable.

                  Comment


                  • #11
                    Doofus's comment is correct.
                    If you look, the inside of the teeth and the outside of the teeth are worn with no full tooth contact. A bad cam gear from the start.

                    Not sure which is which, but but upon acceleration one side is worn, upon deceleration, the other side is worn. This indicates a badly machined gear, and NO, I would NOT continue to use this gear. The pattern wear is excessive and very bad.

                    The galling is somewhat normal, but on the outside (or front) of the gear appears worse than the inside (or back) of the gear. Again, normal wear for a mis-machined gear.

                    Al - Time for another gear (even if only one tooth was chipped), if you ask me.

                    Mike

                    Comment


                    • #12
                      Originally posted by JoeHall View Post

                      Sorry but that excuse is feeble. No reason to have to break a cam gear in, if it fits as it should. Sounds like a BS answer given by someone who maybe produced the gears. Unacceptable.
                      If I recall well, I heard this about Panhard engines equipped with an aluminium gear instead of celoron. As these were used on a delicate engine, this might have been extra safety from the part of the manufacturer. Of course, I do agree with you, Joe. Such parts should be perfectly machined.
                      sigpic

                      Comment


                      • #13
                        By any chance did you install one of the repop crank gears? I have had issues with them.
                        78 Avanti RQB 2792
                        64 Avanti R1 R5408
                        63 Avanti R1 R4551
                        63 Avanti R1 R2281
                        62 GT Hawk V15949
                        56 GH 6032504
                        56 GH 6032588
                        55 Speedster 7160047
                        55 Speedster 7165279

                        Comment


                        • #14
                          That also looks like a repop cam gear. The quality control on both the repop cam and crank gears are suspect. At this point, I only install good used aluminum cam gears and good used crank gears. I have had better experiences with good used.
                          78 Avanti RQB 2792
                          64 Avanti R1 R5408
                          63 Avanti R1 R4551
                          63 Avanti R1 R2281
                          62 GT Hawk V15949
                          56 GH 6032504
                          56 GH 6032588
                          55 Speedster 7160047
                          55 Speedster 7165279

                          Comment


                          • #15
                            Originally posted by JoeHall View Post
                            I have heard lotsa stories over the decades of repro aluminum cam gears that were defective. Stories included high pitched whine, and gear teeth failure. Interesting to note, on yours, all broken teeth and tooth wear/contact patterns are on the front side of the gear. This would be cause to suspect the aluminum gear. With a fiber gear, you could do a comparison of fitment and teeth contact patterns.

                            Other than a defective aluminum gear, about all that's left is a line bore that resulted in the crank and cam being too close. I'd explore the possibility of a defective gear first.
                            I completely agree with Joe (for whatever that is worth).
                            Gary L.
                            Wappinger, NY

                            SDC member since 1968
                            Studebaker enthusiast much longer

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