<VV> Re: bolts loosening

[djtcz at comcast.net]

------------- Original messages, snipped  -------------- 

> There are several places on the Corvair motor and transaxle where bolts or 
> nuts can back off or gaskets can compress in time and leaks can occur. Two 
> good examples are the Trans to Diff bolts and, of course, the valve cover 
> bolts. > In many years of racing, I have cross-drilled the heads of some bolts and > nuts to allow a proper safety wire installation. A proper safety wire 
> installation retains the torque on an already-torqued fastener - the wire, when 
> tensioned, pulls the head or nut in a tightening direction. (For complete 
> coverage 
> of this subject, see "Prepare to Win" by Carroll Smith). The reason for this 
> post is a new Harbor Freight catalog has Safety Wire Twister pliers for 
> under $5. I have had Safety Wire pliers and a coil of the deformable wire in my 
> tool box for 25 years. If you don't, this looks like a good time to add it! 
> Harbor Freight item number is 45340-3AKB - $4.49 - Since I already have a 
> good one, I will probably not get a second, but I am sure a few other items in 
> this catalog will find there way into my garage. If you have a Corvair-powered 
> race car, make sure your valve covers will never leak by changing out to 
> short 1/4-20 studs and tall cross-drilled nuts, safety wired tight. 
> 
> - Seth Emerson 
> 
> 
 >> Hey Seth, 
> For those who haven't used it before, done right, there ABSOLUTELY no way that  nut or bolt is going anywhere. The only limitation is needing two attach points,  one for each end of the wire. AIrcraft use stainless steel wire, but 
> ground-bound applications wouldn't require it in areas not prone to rust. 
> Stainless isn' t the cheapest, but one roll lasts a lifetime. 
> I especially like your treatment on the valve covers, given that this is a 
> problem area. 
> 
> Chuck Kubin 

Safety wire does keep bolts/screws from unwinding.

But on a gasketed surface it would merely keep the bolt from un-winding when the gasket crept after initial compression.  This would keep the situation from getting worse, but the initial gasket compression can be pretty significant.  I carefully torqued the bolts on the rugged cast oil pan  to the  MAX factory spec  on an old (oops,  1976 ain't old in Corvair years) BMW motorcycle with a brand new OEM gasket (thick gray composite).  When I checked the torque the next day (never ran the bike) all the bolts were way under the MINIMUM spec.  After 2 or 3 re-torques it was stable
Structural joints too can loosen with NO bolt rotation.  Joint face Surface dings and no washers under bolt heads can result in significant loss of preload.  My favorite surface prep/surface flattening tool is a big fine mill bastard file.  Small Stones or polishing cloth really can't true up a surface.  2 or 3 gentle full coverage passes with a big file quickly reveal and correct lumps and mounds, and reveal gouges and low spots.  Pressed steel pans and covers usually need local straightening first, which suggests to me they need reinforcement (like the valve cover clamps) to provide even clamping.