I've read a few threads about the plugs, but there were some competing opinions, so I would like to ask for the latest thoughts.
1. What sealant should be used? One thing was clear - NO TEFLON. The most compelling suggestion was JB Weld. Is that a reasonable solution?
2. What kind of plug? Many opinions say NO to brass or aluminum because their head could be easily stripped. Steel was suggested. How about stainless? Any issue with the different expansion rates between the case and the plugs?
One thing is clear - they should be replaced. Of the 11 plugs, 2 almost fell out. They were definitely potential sources of future leaks!
Thanks for your thoughts!
https://lnengineering.com/type-4-store/type4store-products/oiling-system-accessories/galley-plug-set-non-full-flow.html
I just put these in an engine I'm rebuilding.
http://www.914world.com/bbs2/index.php?showtopic=274249&hl=oil+galley
LN engineering also has a non full flow set. 5 steel plugs. I am working on my second engine now. Don’t remember if i used sealant last time. If i did it was whatever Jake recommended.
Steel plugs work fine, when you tap make sure it deep enough that the plug sits flush or almost flush, very important with one flywheel side plug. Liquid teflon is OK just not the tape. I don't like JB weld for this as you may need to clean them out next rebuild.
Only the 5 plugs, 3 behind the flywheel and the two at the front need to be done.
I'll stir the pot.
Aluminum plugs are my preference. In my engineering judgment there is no point mixing dissimilar materials when it comes to galley plugs. Not saying steel can't be used, Per Mark's guidance and tribal wisdwom, others most certainly have been used steel with success.
My reasons for my perference of aluminum plugs:
1) The factory plugs are aluminum. Why? To avoid the potential for leakage that can occur with dissimilar expansion rates. Granted, the OEM plugs are press fit and has a different type of failure mode than the threaded interference fit of a NPT plug. NPT is less likely to leak than a press fit but NPT's and associted tapping operations x 11 holes would have been more expensive to use in production.
2) Potential for galvanic corrosion increases with dissimilar materials. Negligible concern for sure but why add potential for galvanic corrosion in a pressured, potential oil leak path.
3) I've heard the complaint that Aluminum NPT hex's strip. I've never had this problem of stripping an aluminum hex on installation. As with the factory galley plugs, my view is that installation of the Aluminum NPT should be permanent. If the orginal set has been undisturbed for 45 years, I'm not going to plan on ever removing aluminum NPT's after a rebuild. Sure an engine could blow and there would be the need to reclean the galley but I'm not going to plan for that kind of catastrophic failure - the factory didn't nor will I. If need be, the aluminum NPT's can be machined out and replaced later, assuming the case was even still salvageable.
4) My preferred install method ensures a light shrink fit (same as the OEM plugs) in conjuction with the NPT. Put the oil galley plug in the freezer (that's why some call them freeze plugs Just kidding . . watercooled thing I know ) for about 1/2 hour before you need them. Lightly heat the case with a torch. Doesn't need to be raging hot (200F is plenty) so let's not start debating about warping cases. Now thread in the the NPT plug quickly with just a light dab of blue Locktite mostly for lubrication purposes to ensure no thread galling occurs on install. As the case cools you'll end up with a light shrink fit.
Now as the case expands and contracts you have identical expansion rates, a light shrink fit, the benfit of multiple threads as a labrynth seal, a bit of locktite as thread sealant. It won't leak. And as an added bonus, that plug isn't coming out on its own - ever But, as noted above, don't expect to remove it easily in the future. Aint' gonna happen. It will have to be machined out.
Again not saying steel can't work, just that aluminum is my personal preference.
In this case it doesn't really matter which material you use, I only use steel plugs because one day I may have to take them out. Like with most engine builders it's hard to change the mindset when you have a solution that has worked for years, not to mention the couple hundred steel pipe plugs I have in stock. The dissimilar metals/leakage theory is just a no go with my thinking, metals don't expand in just one direction, they expand in all directions. If anything the pipe plug gets tighter as heat increases. I've never had a steel plug leak and I've done this mod on many of my own and customers engines. BTW the steel plug will never rust on the business side.
The pipe plugs I use have the micro-encapsulated thread sealant already on them, same as the 996 factory bolts. Took me awhile to trust this treatment, but they have never leaked. Tech tip if you get these plugs, is use a spare/bare plug to test fit the depth of the plug, then once happy install the ME plugs.
Always use a new or sharp 3/8" NPT tap, you drill to 9/16" and try to oval out the top hole, but best way is to carefully use a taper ream for proper size. I've cut the tip off of my reamer so it doesn't go in too deep. Lube the tap, there are special cutting lubes if you have them, but WD40 works good enough. Always check your test pipe plug depth as you cut with your tap. Don't worry about threads into a galley, but there's a blind plug in the front and one in the back, so don't drill in too far. The most outward hole (3-4 flywheel side) the plug must sit flush or just a hair proud or it will hit the flywheel. I leave the rest of the plugs a bit proud. There's holes with galley right behind them, the 1/2 flywheel hole (IIRC) is a hole really close to a cam galley, leave the plug almost half proud or some builders back cut the plug. Never over torque the pipe plug, but I know I put more torque on a steel plug than you ever could on an aluminum or brass plug. One thing I've never measured is the torque, the plug just stops in the taper, I give one more try and you're done.
Do install all the plugs before you start engine assembly, if there's any issue with depth you want to know before assembly.
empi makes a nice assortment set
Thanks for all the help, it was very useful.
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