[Fot] thread sealing

[greg]

Hey Group,
     I know we are all victims of the British car oil leak legend even 
though the amount of oil leaked by British cars pales in comparison to 
the amounts leaked Chevys. GM didn't stop using rope seals on the small 
block until 1983. Most British cars at least used rubber lip type seals 
by the mid '60s and that labyrinth seal on the TR2-4 is a very effective 
seal when manufactured and installed right. Modern steam and gas 
turbines sometimes use them. We don't have to keep contributing to the 
legend if we use modern sealants. Since my day job is designing 
hydraulic systems I have some experience at keeping oil from returning 
to mother earth.
     The best sealant for pipe threads or straight threads with a washer 
under the head (extremely dumb way to do it but we are stuck with that 
on several TR places) is the Loctite PST series - I like the 567 PST hi 
temp because it is good for 400 degrees F. Get the threads as clean as 
possible by flushing with brake clean then run a small amount all around 
the bottom of the male thread and screw in by hand. Tighten moderately 
tight with a wrench and it will not come loose or leak. If you want a 
fast cure use the 7649 primer. The PST product is anaerobic (cures in 
the absence of air). Loctite used to claim 1500 psi immediate capability 
with hand tight and 15,000 psi after 24 hour cure. You will not find 
that published anymore for liability reasons. This product has small 
teflon particles in it to help lubricate the threads for installation 
but the particles are small enough not to harm anything we have. The 
dissassembly torque is only 150% of assembly so it comes apart easy. 
Uncured PST will flush away with brake clean. At this point I have to 
say something about Teflon tape - use it only as a last resort. IT IS 
NOT A THREAD SEALANT. It is only a thread lubricant to allow the tapered 
pipe thread to be screwed in further - possibly splitting the thread 
boss. I have had more than a few customers wanting a warranty for a 
"casting flaw" at the thread boss.
     Another use for PST is to wipe it on top of an AN fitting with a 
damaged seat. Works most of the time at our low pressures. I use it 
under the large washer and nut on the half shaft, transmission, and 
pinion flanges. It is particularly good at sealing up compression 
fittings which are damaged. I have sealed many straight thread, through 
bolts into oil passages and cavities like crankcases. I once built a TR3 
motor that didn't leak a drop of oil on the guy's garage floor for three 
years and he actually put about 8k miles on it (the car not the floor).
     If I think of more oil sealing tricks I'll send them out.

Greg Lund