280zex Posted September 9, 2011 Share Posted September 9, 2011 Been chasing a drivetrain gremlen. I found out last night that all 6 flywheel bolts were loose and ate the clutch friction disc.. I torqued them to 80ft lbs and have only 8k miles on them, however they were used but in good shape. A few of my other car buddies said that they always used new flywheel bolts. I have never had this happen on my Z before. Mabe my torque wrench is faulty?? I wish I would have checked the flywheel bolts before the trans went into the shop ;( So now I guess I need to get new bolts anyway, 2 of the bolts are missing most of the head from gringing on the clutch disc.... AAARRRRRRRGGGGGGHHHHHHHHHHHH!!!!!!!!!!!!!!!!!! Am I ok to re-use flywheel bolts or get new ones?? I have others in the bolt bin.... Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted September 9, 2011 Share Posted September 9, 2011 I would go to the local hardware store and get some grade 8 bolts and lock washers that have the correct length, and make sure that you use new grade 8 lock washers. If they backed out before use some locktite to install the new ones. Make sure that your torqued to 80 foot lbs and not 80 inch pounds. Scott Quote Link to comment Share on other sites More sharing options...
Leon Posted September 9, 2011 Share Posted September 9, 2011 FWIW, there is no "grade 8" in metric fasteners. Metric class 10.9 would have similar strength to standard grade 8. Getting metric class 8.8 hardware would be like using standard grade 5. http://www.k-tbolt.com/bolt_chart.html Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 9, 2011 Share Posted September 9, 2011 Yes, you can reuse Datsun flywheel bolts, but not after they come loose, so go get some new ones. Red loctite and torque in thirds in a crisscross pattern like you would a lugnut is my way of doing it, I've never had them come loose on me. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted September 9, 2011 Share Posted September 9, 2011 (edited) I reused them on my stock engine, and it's held up for 20k miles. I bought new ones for my high comression enigne. Metric grade 10.9 from a store that only sells nuts and bolts. Edited September 10, 2011 by BluDestiny Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 10, 2011 Share Posted September 10, 2011 Lockwashers....don't! Take a look online for a video of a "Junkers Machine" doing fastener testing. This is exactly the environment your flywheel is in in regards to relative movement. The Diesels are worse, and imagine that, they have a single pin to take shear loadings and stop the relative motion of the bolted parts. The best way for a fastener to not come loose is proper preparation of the surface, proper bolting to insure adequate clamping and proper preload of the fastener. There is another website...maybe the Junkers Machine is on it: "Bolt Science"---there is a lot of good information there that will dispel the myths surrounding what you should to to get a bolt tight and keep it that way! One of the facts they provide is the breakdown of what torque really is: quantification of friction under the head of the bolt, friction on the threads, and actual elongation of the fastener (actual tension)...alter either of the frictional coefficients by using the improper lubricant (or using lubricant when it should be torqued dry) and you over-stress the fastener leading to deformation, loosening, or outright breakage/failure! Flywheel bolts are something you want to not have cracking off and letting their bolted component fly off someplace! I believe ARP now offers 12 point headed Flywheel Bolts for our L-Series Engines... I'd use them if they were available. Very nice quality control. I'm actually pushing my company to use ARP to make some of our fasteners for impeller studs as they have the technology to roll threads in Aermet Material. Talking with those guys is always a learning experience. Quote Link to comment Share on other sites More sharing options...
280zex Posted September 12, 2011 Author Share Posted September 12, 2011 (edited) ok so it was due to a faulty torq wrench. My wrench was 15 ft lbs lower than spec. So I got new bolts, cleaned out the bolt holes in the crank, and got some red lock-tite. Torqued in a star pattern, 20-40-60-then 80 ft lbs. Good thing I realy inspected things as my back-up flywheel had a nasty little crack in it! What I dont like is the new clutch. I was running the like-factory exedy for 280zx turbo disc and pressure plate. That didnt like my extra boost, and was kinda slipping up realy big hills under load. I think it was rated to hold 250 ft lbs torq. My new exedy is rated for 400 ft lbs torq. It does NOT like trafic at all, its either in or out no slipping. As long as I kinda launch the car its ok but if I'm easy in it I get nasty chatter. Gona adjust the linkage and see if I can get a better feel for the new set-up. Whats odd is that it takes less pedal movement to work the new clutch, doesnt give much room to work the left foot, mabe 1/2 inch of movement once the pedal feels firm. Heck the clutch in the last race car I worked on was more freindly.... Thanks Tony that web site Bolt Science is awesome! Boy did I learn alot, now to go fix some in-correctly applied bolts in the car.. Edited September 12, 2011 by 280zex Quote Link to comment Share on other sites More sharing options...
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