Teflon Tape ... or not

I'm replacing a fuel pressure regulator on a 3 deuce set up. The fittings are the usual 1/4 and 1/8 inch tapered thread fittings. I previously used Teflon tape on the threads, but have since read (somewhere) that the use of Teflon tape on such fittings is not only unnecessary, but is not recommended. Anyone have advice/experience with this?

I need all the help I can get,

Grog

Avoid its use if at all possible. Problem is when not installed correctly it could get into the fuel line/system and wreck havoc.

I use Teflon tape, not that hard to do correctly. I don't use it on electric senders though.

My personal experience is that pipe threads on soft (brass) fittings seal tightly with no added tape or dope. For cast iron pipe threaded fittings I find that pipe dope/compound works better than teflon tape. So I've stopped using teflon tape.

Unless they are special 'Dryseal Tapered Pipe Threads' or 'British Standard Parallel Pipe Threads with a gasket', some sort of thread sealing is needed.

Teflon tape is properly installed by making sure that there is no tape on the thread groove that is closest to the open end of the male fitting. That way, there is no chance of any loose bits of Teflon entering the flow stream. Three turns of tape is more than sufficient and two will usually be fine. To avoid confusion on which way to wrap the tape, I always hold the tape and turn the fitting clockwise to "screw" the tape onto the threads. If you undo a fitting, make sure that every trace of tape is removed from the female side. Use a needle if needed.

Dryseal fittings look the same as normal tapered pipe threads (but may feel sharper) and have a slightly different thread form that deforms when installed thus making a good seal. But I have had no luck using them the second time after the threads have been (intentionally) mutilated.

My personal experience is that pipe threads on soft (brass) fittings seal tightly with no added tape or dope. For cast iron pipe threaded fittings I find that pipe dope/compound works better than teflon tape. So I've stopped using teflon tape.

A quick look at the McMaster catalog shows that most small brass NPT fittings they sell have Dryseal treads. So ply33 experience may be related to this threadform.

I have always held the theory that the sealer is used more as a lubricant than a sealer. I always use something even if it is only spit.

heres a good llink for you from a manufacture of pipe thread fittings.

http://norcal.swagelok.com/blog/bid/88017/Skill-Applying-PTFE-tape-to-tapered-pipe-threads

I use teflon tape all the time BUT when using tape on threads, no matter what, leave the first thread bare so there is no possibility of errant tapes fragments getting where they don't belong.

Nothing beats aviation Permatex...................Bob

I use teflon tape all the time BUT when using tape on threads, no matter what, leave the first thread bare so there is no possibility of errant tapes fragments getting where they don't belong.

Totally agree !

Well said !

Wayne

Sometimes I use one turn of teflon tape or just a smidgin of dope. When you are working with pot metal, any additional material between the fittings may mean the difference between snug and broke. Zeke

DriveAG.......Because some people miss it.......as I apparently did.......

Well, according to the good advice y'all have given, it seems that I've been using the Teflon tape more or less correctly (dumb luck). I'll certainly pay much more attention to how I use it from here on out.

DriveAG, I really appreciate the detailed information that you posted and will follow your advice in the future. I wasn't even aware of the existence of dryseal fittings and doubt that I'd be able to recognize one unless it had a label attached. Due to my excessive tinkering, most of my fittings have been previously assembled ( I assemble, disassemble, assemble ... repeat endlessly it seems); consequently, I'll probably continue to use the Teflon tape on fittings ... dryseal or not.

Counterpoint, thanks for the link.

Thanks, everyone, for your help,

Grog

I use a sticky stringy Purple thread sealent that doesn't get hard, on everything (I can't recall the name). It's available at NAPA and works on oil, gas and antifreeze. I used to use permatex which works well on gas and oil but not on antifreeze, but after finding the purple stuff I only have to have one product handy. It works awesome on gaskets as it's very tacky, making the gaskets stay in place while assembling stuff.

Good info in this thread about the proper use of teflon tape. I'll just add that I've been using teflon tape on sending units for four decades with no issues about electrical conductivity. The threads always cut through the tape sufficiently to make contact.

I use Teflon tape, but this is my favorite stuff to use.

http://www.permatex.com/products-2/product-categories/thread-compounds/thread-sealants/permatex-thread-sealant-with-ptfe-detail

All of which brings up the question,

Does anyone use tape (or dope) on pipe-threaded spark plugs such as found on Model T and many other early cars?

I have no experience with Model Ts, but have never used any sort of thread treatment on the spark plugs of my older cars. I usually coat the threads of the spark plug lightly with oil, just to help ensure consistent torque values. On the "older" cars I've worked on, the seal is provided by the copper "crush" washer, not the threads. Teflon tape working temperatures range from -100*F to around +500*F, and reportedly will melt at around 620*F. I've measured (infra red thermometer) the idling temperature of the exhaust manifolds on my small block Chevy at around +500*F, so I'm guessing that cylinder temperatures will be somewhat higher ... at or exceeding the working temperature of Teflon tape.

When installing spark plugs in the aluminum heads of my "newer" engines, I use a light coating of "never seize" compound on the spark plug threads.

Cheers,

Grog

In professional motorsports, some shops have a practice to never allow thread tape in the building or on the transporter. Then it can never find its way onto the race car, where a hurried application in the heat of the moment could produce a blocked fitting. Instead, liquid sealants are used.