Core plugs

[ndutton]

Studying the gorgeous Moyer engine pictured in the panorama on the home page I noticed the core plug beneath the temperature sender is reversed from the two in the manifold and the two in the head.

I just checked another engine, the two in the manifold are the opposite of the other three.

Is there a reason?

[BunnyPlanet169]

?

Looking at the panorama, I'd say the temperature plug recess was deeper, but domed surface of the core plug was facing out as you'd expect. Is that what you meant?

I believe the correct installation is dome out, lips in, no?

[ndutton]

My interpretation of the picture is the odd plug in question is dome in-lips out. The other A-4 I checked had the manifold plugs installed the same way. Nobody ever taught me a right or wrong way so I've always installed them dome in-lips out for ease of centering a socket to drive them in.

Seems to me every factory core plug I've ever seen on automotive engines was dome in. I've never had a problem so I'm wondering if it even matters.

[BunnyPlanet169]

The split hair in question

FWIW, zooming, I would think the dome is out.

I cannot speak with authority about polarity, so I won't!

[ndutton]

Yeah, I didn't zoom in, trusted my questionable eyesight. But the question lingers, does it matter (see automotive comment previously)? If it does, I'd like to know. If it doesn't, that's good info too.

[edwardc]

I once saw a watchmaker's tool for inserting the crystal face onto a watch. It had a set of matched domed/dished faces that were a slightly shorter radius than the crystal's. Squeezing the crystal in it would flex it and reduce it's diameter just enough to insert it into the groove in the watch body.

So I would think that the dome-out position would allow pressure (such as that caused by freezing) to loosen the plug and allow it to come out.

But this same effect would make it slightly harder to insert them that way.

Dome-in sould make installation easier, but take more pressure to pop it out.

But maybe the effect is not significant since we're installing it in a smooth bore and not into a grooved/notched hole.

EDIT: After posting I found this article: "A Core Plug is not a Freeze Plug"

[BunnyPlanet169]

Different plugs...

If it's a flat disc, then dome out and expand with a (experienced) tap to the middle.

The MMI plugs have skirts. I suspect they can go either way, as long as the cavity is deep enough to handle the dome in condition. I suspect they seal more as a function of skirt pressure from deformation, than diameter expansion like the discs.

But again - I don't know!

[ndutton]

EDIT: After posting I found this article: "A Core Plug is not a Freeze Plug"

Yeah, we've visited that before.

http://www.moyermarine.com/forums/showthread.php?p=71081&mode=linear#post71081

Notice that I never used the phrase freeze plug.

I've had zero problems ever and in light of the automotive installations I guess I'll continue on as before. We operate at or very near zero pressure in the cooling jacket anyway.

[BunnyPlanet169]

According to Ford

I guess it depends on the style of plug....

http://www.justanswer.com/ford/2l5v7-lift-engine-change-freeze-plugs.html

And neither is the domed disk which requires a punch to the center....

What's interesting to me is that the sealing edge is not the knife edge of the skirt, but the shoulder body of the skirt. Add Permatex...

And another good picture and description....

http://www.autozone.com/autozone/repairinfo/common/repairInfoMain.jsp?targetPage=productsHowToInspect&leftNavPage=productsHowTo&pageId=0996b43f80a013d3&subtitle=replace