Sealant for NPT plugs in cam tower

['78 SC]

What are you using to seal NPT plugs installed in the cam towers? I'm building an engine for my track car and I tapped the cam tower openings for NPT plugs to facilitate cleaning the spray bars. So far I've only facilitated leaks.

A search here shows a variety of sealants used for threaded and plain plugs: none, blue/red/orange/green Loctite, Permatex Aviation ("camel snot"), anti-seize (?).

Obviously the sealant has to stand up to 200F oil at 2-3 bar. Any recommendations?

TIA,
Steve

[dannobee]

Loctite 592 for <400F. It hardens up. Loctite 567 for <300F, it doesn't harden up.

['78 SC]

Originally Posted by dannobee

Loctite 592 for <400F. It hardens up. Loctite 567 for <300F, it doesn't harden up.

Thanks for the response, Dan. Given the location, I'm opting for the higher temp 592. The torque properties are in the datasheets; neither one should interfere with removing the plug later on.

Here are some details for anyone else with a similar need:

Loctite 592 Datasheet
The high lubricating properties of LOCTITE® 592™ prevent
galling on pipe threads and fittings. It will provide immediate
low pressure sealing and allow the readjustment of fittings
shortly after assembly. After 72 hours the joint is sealed to
pipe burst pressure. This product is typically used in
applications up to 204 °C. T

Loctite 567 Datasheet
LOCTITE® 567™ is designed for the locking and sealing of metal
tapered threads and fittings. The product cures when confined in the
absence of air between close fitting metal surfaces and prevents
loosening and leakage from shock and vibration. LOCTITE® 567™
provides robust curing performance. The high lubricating properties
of this compound prevent galling on stainless steel, aluminum and all
other metal pipe threads and fittings. It not only works on active
metals (e.g. brass, copper) but also on passive substrates such as
stainless steel and plated surfaces. The product offers high
temperature performance and oil tolerance. It tolerates minor surface
contaminations from various oils, such as cutting, lubrication, anticorrosion and protection fluids

[PeteKz]

Teflon plumbing tape works pretty well too, and doesn't seize.

[dannobee]

What auto manufacturer recommends teflon tape on anything? The vast majority of them specifically forbid the use of teflon tape because the little shards can end up plugging things.

Paste yes. Tape no.

[Henry Schmidt]

At Supertec we hate oil leaks. It's like a religion to us.
Over the years we've developed a habit of using a light smear of 574 Loctite on all fitting threaded and pressed fitting that constitute a potential oil leak. Even those fitting that use an aluminum or copper sealing ring. One exception is the crank plugs. For those we use LT high vibration green.
It's a technique taught to us by one of the world renowned Porsche engine builders, Dean Polopolus (Polo Fame). Simple, reliable and easily removed.

['78 SC]

Henry,

Just to clarify, LT Green on the crank plugs because you want its strength and high prevailing torque to keep the plugs in place and LT 574 everywhere else because only the sealing (not retention) properties are needed?

[Dpmulvan]

Originally Posted by dannobee

What auto manufacturer recommends teflon tape on anything? The vast majority of them specifically forbid the use of teflon tape because the little shards can end up plugging things.

Paste yes. Tape no.

Tape is fine for cam tower plugs if you know how to use it, it’s not the space shuttle.

[Henry Schmidt]

Originally Posted by '78 SC

Henry,

Just to clarify, LT Green on the crank plugs because you want its strength and high prevailing torque to keep the plugs in place and LT 574 everywhere else because only the sealing (not retention) properties are needed?

Yes

[Henry Schmidt]

Originally Posted by Dpmulvan

Tape is fine for cam tower plugs if you know how to use it, it’s not the space shuttle.

You are correct. These old lawn mower engines aren't rocket science and yet, mistakes come out of pocket not some government budget.
Best practices when available either by experience or manufacturers specification are advised.
In 40 years and over 450 air-cooled engines I have never seen a good application for Teflon tape.

[Dpmulvan]

Originally Posted by Henry Schmidt

You are correct. These old lawn mower engines aren't rocket science and yet, mistakes come out of pocket not some government budget.
Best practices when available either by experience or manufacturers specification are advised.
In 40 years and over 450 air-cooled engines I have never seen a good application for Teflon tape.

Well if your going to use a national pipe thread plug on your cam tower.