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Core plugs/freeze plugs

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J

JTSchmid

Freshman Member
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Hi,

I'm sure this has been talked about before. I've heard horror stories of core plugs coming out, has anyone installed threaded plugs in Healey engines. I've been contemplating installing either tapered or o-ring boss type plugs. Any feedback would be greatly appreciated.

Regards,

Jim
 
They're able to be forced out for a reason; to avoid cracking the cast-iron cylinder block should the coolant inside freeze and expand (7%+- rate of expansion).

The only time I EVER had one (1 only) come adrift was when I let an MGB sit at my place of employ, and we had an overnight freeze sufficient to force the plug out. I was working in the Gulf of Mexico at the time, and really didn't think much about it freezing in New Orleans.

My recommendation is to fit them with a thin film of the "old style" non-hardening brown Permatex sealer. They must also be "mechanically" seated properly (BFH). I've been doing them that way for close to forty (>40) years, and no comebacks.

They're called "freeze" plugs (or "expansion" plugs) for a very good reason...
 
I've been told that the holes were really required in the casting process as opposed to them being freeze plugs, else why so many when one would do?

In any case I blew two of the flat type that are peened into place out of my Elva MGA engine when running in successive sessions for the first time after a fresh rebuild, and now use only the brass Balkamp type which uses a disc and a backing plate that is pulled up tight and jams the disc in place via a hex nut in front. I clean around the hole very carefully set them in 5-minute epoxy and then tighten them using two wrenches as tight as I can. So long as they are in square I think they are in there forever!

This is one of those jobs that is best done before the engine is reinstalled because it is tough to get a good angle on the nut with engine in situ, but I have also done them at the track on a few occasions. Luckily I have always blown the plugs along the side of the engine--there is one that is in the back face of the engine and that would require pulling it out, all for a blown plug!

I also tried (on a junk block) tapping the holes and plugging them with a conventional tapered pipe plug but found that the way the holes were cast it was impossible to get a drill to bite evenly to give me a clean hole into which I could run a tap.
 
I've had them blow out from overheating and leak due to rusting from neglect. If they blow out from freezing, the core plugs may be the least of your problems. The ones you can access easily probably are best replaced with the original peen in type. Where the are not easily accessible, I have had good luck with the metal backed rubber expandable type.
 
Properly installed, cup or disc type last a long time unless you have a rust problem in cooling system,I have a Matco kit w/adapters&swivels to enable proper install. Rubber plugs can weep& come out at the most inopportune time.Been there, done that! Genos2
 
Hello :savewave:,

the story of the freeze plugs is a fairy tale. The holes are only to remove the sand after the casting process.
Some engines without coolant are exploded in a cold winter and safe the block...so the people believe this is a freeze plug... :thumbsup:
I can`t believe how much rest of sand and rust I removed if I flow my block with a high pressure cleaner .

Anyway,about your question. I removed all plugs, because the rust works from the inside slowly to the outside. I use the pot-type because there are original on my engine, and there are easier to get sealed.
The flat cover-type is not so easy to get sealed and get fit.
Before the press in process with a hex nut bit ,I clean the holes seriously, than I dispense very thin layer silicon based sealing (for this application) in the holes.
I have no long term experience, but I believe it should work over live time.

Bye michel- who like original solutions
 
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