| Author | Message | ||
| Paul Newman (Newman)
Junior Member Username: Newman Post Number: 91 Registered: 12-2001 |
Anytime you torque a fastener, the bolt or stud stretches. That stretch is what keeps tension on the nut or bolt itself which prevents it from backing off again. They are supposed to return to their original length when unloaded, as long as they werent overtorqued in the past. If they are torque to yield bolts, then replace them. They only get used once. If the torque spec doesnt call for an additional number of degrees of rotation of a fastener after the torque spec is set, then they arent torque to yield. Was it just not torqued correctly in the past? If you replace the main studs, will you have to align hone the main saddles? Probably. When retorquing the mains, you will know if the stud has been stretched beyond its limit by the "feel" or you can measure the stud stretch with a special tool, which not too many people are going to have lying around. I would bet the mains werent torqued correctly and I would reuse them. Paul | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1615 Registered: 12-2000 |
Some nuts do deform. Those bearing cap nuts were also like the rod nuts, they are a self-locking type, see my previous post why they are loose. After all of this rebuilding, now you know what kind of work to get into = $$$  | ||
| Mitchell Minh Le (Yelcab1)
Junior Member Username: Yelcab1 Post Number: 56 Registered: 11-2001 |
Peter' The rod bolts and nuts stayed tight. I would probably replace the nuts anyway. It is the 10 big 19mm nuts that hold the Crank Shaft bearing Caps that came loose. Should I replace those? Nuts normally do not stretch, and the studs do not stretch as a rule. If I don't replace the bearing cap nuts, is there a thread locker compound that can be used in that environment? Locktite xxx? I am way ahead of the game, yes I know. And Techcraft is not getting one red cent from me. $90 an hour to disassemble the head, geez, I don't make $90 an hour in my job. | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1613 Registered: 12-2000 |
Just remind yourself what this whole job would've cost if you never got your hands dirty . You're way ahead of the game, but that quote was over the top, keep looking... Its been debated here before about whether to re-use studs/bolts or replace. I'd automatically replace the rod bolts/nuts: when first torqued, they stretch. This stretching keeps the nut tight (although the nuts do have castellated tabs which I imagine also provides some form of locking). If you re-use them, they stretch too much and are now weakened. Also the nuts would loose that tab locking and it too wouldn't stay tight. Probably that's why you came across all of those loose ones, the previous guy may have reused the old fasteners. You've seen the discussions here about the cam drive pulley bearings, so it would be the best to replace them all (and install sealed bearings in the front). | ||
| Mitchell Minh Le (Yelcab1)
Junior Member Username: Yelcab1 Post Number: 53 Registered: 11-2001 |
I bought a winch, hooked it to the top of the garage and it helped in separating the tranny from the block. I proceeded to remove the front plate, the crank shaft caps, the pistons, and the crank shaft. It was a good thing that I decided to do a full rebuild because I found somethings in the engine that was disturbing. Three crank shaft nuts were not torqued right and came loose by hand. Three others were not at the right torque and came loose with a twist of the wrench. The person who did the engine work before did not do it right at all. Do I need to replace the crank cap nuts as well as the rod nuts? Anyway, the crank shaft is in good shape, needs to be polished, cleaned and that is it. I do need all new bearings though. The cylinders are all good, and the rings are too. But I will check them out throughly before reusing them. Now that I got the whole thing apart, what other bearings (like pulley bearing, pilot bearing, and so forth) should I just go ahead and change? This weekend I am going to disassemble the heads to see what valves need to be changed. Then, next week I will clean all the parts and do a measurement of all the critical components to see if everything is in specs. This project is getting ... fun. Except for the $2000 quote from the machine shop to do a regular head job, without any parts. That is ... just an insult to a home mechanic. |