Ok to give you a brief history, 8 months ago, I help replaced a motor on an 85 Z28 (305TPI). At the time member had no reverse on his tranny (automatic). Well he took the car to Texas for school and came back just this month. We went ahead and replaced the tranny and also installed the corvette servo. (A THANK YOU goes out to GMTech for his intuitive instruction on this subject matter.) Member never really drove the car hard (pedal to the metal from a dead stop) Upon installing the tranny, we set the T.V. cable and proceeded to adjust as necessary. We floored it from a dead stop and spun the tires. (Just to see if the corvette servo really would spin the tires. I would advice anyone to get the corvette servo if they are looking to upgrade their tranny) When we test drove the car we notice a slight vibration during the low rpm range but went away at higher rpm. I later get a phone call from the member telling me that something came off his car and continued to drive it another 1/2 mile to his friend’s house. He looked under the car and noticed the harmonic balancer was no longer on the car. I am at a lost as to why the HB had fallen off. We torque all the nuts and bolts as stated in the Chilton’s manual. Anyone have a guess as to why this may have happened? I do not believe the tranny could have caused the HB to come off. I will go to his house tomorrow and check it out. Does anyone know the size bolt that goes from the HB to the crank? Any help I can get would greatly be appreciated. Happy NEW YEAR to everyone..

[This message has been edited by 86z/92rs (edited December 31, 2000).]

[This message has been edited by 86z/92rs (edited December 31, 2000).]

 

Not sure on the length but it should be a 7/16 NF bolt. Go pull one off a car in the junk yard. You'll need a 5/8 socket.

 

about 10 or 15 dollars will get you a new bolt from ARP. i use my 1/2" impact wrench to tighten the balancer bolts and have never had one come off. woner if the threads in the crank are stripped?

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ICON Motorsports
1st & 3rd

 

Are you sure it came with a center bolt? My motor didn't have one. The crank shaft didn't even have the hole for one. Granted this engine is a 327 from a 65 vette but it could be possible on some firebirds. I ended up have the machine shop drill a hole and tap it so I could put a bolt in. I heard some horror stories like yours. Probally didn't happen in your case but something to look for. Also make sure the bolt has enough threads and the harmonic balencer is on all the way.

 

I've seen this happen several times. Most of the time it is due to the bolt having been forgotten. I have personally made this mistake on my father's 67 GTO but the balancer stayed in the car, just hit the core support. It could also be caused by the bolt breaking, the washer not being the right size or not installed or possibly by the crank snout being worn so the balancer vibrates the bolt loose. when you put the new one on, be sure and add some sealer to the keyway on the outside which will prevent oil seepage and also add a little bit more hold on the balancer. I would do the ARP route as well.

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Kyle Osterholt
Okarche, Oklahoma
ASE Master Certified
86 T/A 383 TPI
89 TTA #1002 T-top/Leather
89 TTA #1358 Hardtop/Leather
80 T/A Pace Car
73 Opel GT