In a message dated 1/14/99 5:59:36 PM SA Eastern Standard Time,
gt0003a@prism.gatech.edu writes:
> Matt, if you get new studs for the engine, remember to throw out the
> specs for the original bolts/studs. Companies like ARP will include the
> assembly lube or ask that you use oil during assembly. The lubricants
> basically decrease friction significantly between the threads. Such
> lubricants may reduce the friction and increase the clamping force by as
> much as 75%, therefore meaning that you need to use less torque during
> tightening.
You are correct that clean new threads will allow for more clamping force to
be transmitted due to less friction in the fastener, but IMHO you drew the
wrong conclusion here.
Torque specs are always given for clean lubricated threads. After all the
torque specs for any automotive fastener are written by the car maker. I feel
it is safe to say that when cars are built, the threads are clean and lubed.
<G>
>
> Better than loc-tite would be a good, or even a bad set of tap and
> dies. These are invaluable during reassembly. Many bolts, captive
> nuts, etc. are not wasted and can easily be cleaned up with the tap and
> die. I shudder at the stuff from Harbor Freight, but even a crappy
> Taiwanese tap and die set from them will save you time and money.
These would be good for cleaning up threads.
A few other notes on Loc-tite:
blue (242) is used for most applications. Red (271?) is the super strong
stuff and should only be used in very specific applications. Properly applied
red Loc-tite is stronger that a grade 8 bolt and will take the threads off a
bolt on disassembly (yes really, I have had it happen to me). Green after
lock is used instead of a mechanical bend over tab. The joint is assembled
and the a drop is applied to the exposed bolt end wicking action will pull the
Loc-tite in where it is needed.
IMHO opinion most people that install Loc-tite don't understand how to do the
job properly, and therefore do it wrong. The threads must be totally clean,
both make and female. No dirt, no grease, just clean. Loc-tite primer is
worth the hassle to find and use. It cleans up any remaining crud and acts as
a catalyst to make the Loc-tite cure faster. Without primer Loc-tite takes 24
hours to cure, with primer it takes one. This means that if you are on the
pre-grid and have to screw in a bolt for a race that is starting in 10 minutes
don't bother with the Loc-tite, it is not going to help. Yet, at almost every
race that I go to, I see guys baptizing bolts in Loc-tite that are going to be
in a race long before the 24 hour cure time is up (very few people seem to
know about primer).
Last but not least Loc-tite products turn to powder at 450 degrees F. If you
have a bolt that is loc-tited and you are having trouble doing the
disassembly, heat that sucker, at 450 it will unscrew.
For a really good discussion of torque, fasteners, and other things like that
get hold of Carroll Smith's book Prepare to Win.
Rick Ewald
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