threaded case plugs

wprater · 02-29-2016, 07:32 PM

I have a 930 case for my SC and some of the plugs have been removed and threaded. I have what I think should be the replacement plugs for these, but Im not certain which I should put where, and how I should secure them.

The three plugs should be for the ends of the main case oil channel (flywheel area and cap on reverse side) and a smaller one near the pulley. but what about the one on the side of the main channel in last pic below?

I tried to put them in, but they seem to get stuck partially, do I need to torque harder? And should I use loctite or some other sealant on the threads?

here are some pics. Im very interested in the threaded part on the side of the main oil channel on the side of the case; what do do there??

afterburn 549 · 02-29-2016, 10:41 PM

Pipe plugs, as a rule, should go in three full turns B4 friction is felt. (not a law)
They are tapered so as to get tighter as they go further in.
There are also straight plugs which will never get tight unless they go up against something.
Streight plugs will leak.
Pipe plugs should have a some pipe thread wrapped on them or in oil galley situation, perhaps EPOXY on the threads.
Each method has its merits and opinions .

chris_seven · 01:03 AM

If I used threaded plugs in this location I would always use a tapered plug as they are the only real method to guarantee a good seal.

If you look closely at the plugs you have they do appear to have a taper and they could well have an NPT thread form.

One appears to have a micro encapsulated sealant applied, which means it is dry until torqued and then the small particles break and a liquid sealant is released.

You could apply a Thread Sealant such as Loctite 566 to the other plugs but is shouldn't really be needed.

If you try to overtighten you will just strip the case threads so the only way to make this type of plug a flush fit is to try to buy the shortest plug you can find.

You may be able to find Aluminium Plugs that would reduce the risk of pulling out the case thread but you do need to avoid overtightening.

Wrapping this type of plug in a PTFE pipe tape is also common practice and I would never do this on a plug installed in an oil gallery.

afterburn 549 · 02-29-2016, 10:55 PM

My opinion epoxy is best BUT- you have to keep in mind what you are doing and where a little excess may end up.
In this case hahah in this case simply tilt engine up so gravity works for ya.

wprater · 02-29-2016, 11:10 PM

great info, thanks!! so these must be pipe plugs then. they start to get tight as I turn them a few times as you'd both suggested they might. I tried to turn one with a bit of force, but luckily didn't strip any case threads.

I'll need to get another case plug for the threaded plug on the side of the galley then, as I dont have one of that size.

Mark Henry · 04:09 AM

NPT pipe threads are tapered that is why they get tighter the further in they go.
NEVER use teflon tape, it makes things too slippy and can lead to over tightening the plug and cracking the case galley boss.

In the 3rd pic you can really see a galley in the threads, you must take care not to block this. If blocking the galley is an issue you could notch the plug and index the location. The other way is the plug can stick out proud as long as it is at least half way in. You want the plugs tight, but don't be a gorilla.
Note the plug behind the fan must be in far enough not to interfere with the fan housing. (your last pic, this is the one you may have to notch and index)
I just use loctite (620 is my go to for this), I wouldn't use epoxy on the threads, you could do the exterior if you like. The thread sealant on the one plug in your pic I've never had an issue with, I still use a drop of 620.

Never use aluminum or brass plugs, you will strip out the hex. Different metals expansion is not an issue.
You should have had all your plugs in at the start of the build and checked for clearances before the build.
30 years experience doing this to Type 1 and 4 VW aircooled engines.

wprater · 03-01-2016, 10:32 AM

thanks for the info!! I measured the length, galley inlet depth, and installed depth. things look good!

I've tightened them tight.. one stopped and I snugged it up. the other large one still turns a wee bit.. not sure if I should keep tightening.

this small one I. light today may not be tapered, as it only seems to tighten at end.

Mark Henry · 03-01-2016, 11:09 AM

Try a different plug, it's like A $1.50 don't use that square head plug on an expensive 911 engine build.

wprater · 03-01-2016, 11:46 AM

confirmed that I won't be using that one. they told me at hardware store they were tapered. :/

afterburn 549 · 03-01-2016, 12:39 PM

If i remember , there are different thread pitches in metric. ( Just to confuse ya! )

wprater · 03-22-2016, 01:01 PM

Quote:

Originally Posted by Mark Henry;9018506

...

Note the plug behind the fan must be in far enough not to interfere with the fan housing. (your last pic, this is the one you may have to notch and index)

Mark,

It turns out that plug behind the fan housing is too deep and sticks out more than possible to clear the housing. What do you mean by notch and index? Im looking for a shallower 3.4" plug, but no luck yet.

Mark Henry · 01:56 PM

I've never done the plug behind the fan, but I knew it would be close.
Two methods to get around this, or you can do a combination of both.

1/ Grind the backside of the plug and even the front side as long as you have enough of the hex left to catch the key.

2/ Indexing you can grind a grove the plug so it clears the passage, then mark it (index) for the correct orientation for when you install it.

Doing either of above you the you want to make sure you clean up the threads real good and be positive you can instal the plug without cross threading it. You also want to be sure of depths, etc.
You don't have be a gorilla putting the plug in, but the should be a bit snug. Everyone has there favorite sealants, but I use loctite 620 and have never had a leak on the 3/8 plugs, on the many aircooled VWs I've done.

.

Mark Henry · 03-22-2016, 01:54 PM

dp

ajwans · 03-22-2016, 02:40 PM

Check carefully whether they are NPT or BSPT threads, I think the difference may be 1 thread per inch (18 vs 19)

Ask my why I know this.

andy

Mark Henry · 03-22-2016, 03:37 PM

Yes I'd check to be sure, but BSPT isn't very common in the US.
NPT is the US (North America) common pipe thread.

wprater · 03-26-2016, 02:32 PM

Quote:

Originally Posted by Mark Henry

I've never done the plug behind the fan, but I knew it would be close.
Two methods to get around this, or you can do a combination of both.

1/ Grind the backside of the plug and even the front side as long as you have enough of the hex left to catch the key.

2/ Indexing you can grind a grove the plug so it clears the passage, then mark it (index) for the correct orientation for when you install it.

Doing either of above you the you want to make sure you clean up the threads real good and be positive you can instal the plug without cross threading it. You also want to be sure of depths, etc.
You don't have be a gorilla putting the plug in, but the should be a bit snug. Everyone has there favorite sealants, but I use loctite 620 and have never had a leak on the 3/8 plugs, on the many aircooled VWs I've done.

.

Thanks for the clarification. I will go with the grinding if I cannot find a replacement plug. I don't have the tools for the grinding, so I need to find a local shop that can do it. Have to grind the front, as the back is already pushed all the way through (it's not blocking the inside galley) where it's tapered depth has maxed out.

If I get a shorter plug, the indexing might be needed, as it would probably push through deeper.

eastbay · 10:42 AM

They do make shallow -short length- flush mount threaded plugs that will fit, as I have one in my case. Fits flush, nice and short, no where near the oil passage.

wprater · 03-28-2016, 12:46 PM

Eastbay, ideas on a resource to get this shorter plug? I've tried 3 local fittings stores and some online shops as well.

wprater · 04-05-2016, 01:40 PM

Still cannot find anything shorter than the left plug in the first pic (first post). I shave off 4mm off the top, so it's flush to that case curve, but I think it needs to be almost completely flush to case hole? If I go that far, I surely wont have room left for the allen key. Thoughts?

boosted79 · 04-05-2016, 04:35 PM

No need for the plug to be flush with the case at that location.