Core plug blow out after engine break in?

[Zack Mckellips]

So I broke in the new 383 engine in my 70 super bee two night ago, all went great, broke the cam in, then got the timing and the carb set, then tonight I was playing with the carb, the engine was running, it was only about 180 degree, setting the carb and then the driver side core plug just blow/feel out? was a mess, but now what? the machine shop put them in, I could put more sealer on it and pound it back in, but what says that will work and/or what about the other ones? has any one had a problem like this?

[Chryco Psycho]

it could be a bad plug or not in far enough for the lip to bite into the block , install a new plug with sealer replace the coolant , beats wiping a lobe on the cam by a long shot

[Moparal]

It has happened to me before a long time ago. The plug wasnt set in right. I installed another one and never looked back

[71chally416]

   Might wanna give the others a look too. Better to blow it out in the driveway than going through the lights at the track doing 100mph. 

[moper]

Yup. It happens. The very first engine on my run in stand had a leaky plug. It sure was easy to fix there, rather than have to pull everything off to replace it. Make SURE all the others in the sides of the block are in far enough. If one comes out while you're racing you may go for a wild ride when the coolant gets under the tires.

[femtnmax]

There seems to be 2 ways to install freeze plugs.  One method is to fit a socket inside the rim of the plug and drive it in, so your 'pushing' on the inside cup.  I have seen freeze plugs leak using this method.
The other method is to fit a socket or use the proper tool that contacts the "raised rim" of the plug (the rim around the outside diameter) and drive it in.  Using this method maintains the diameter of the plug.  I have never had them leak using this method.   JMO
It's sort of like packing wheel bearings.  Many ways to do it, or so I hear.  I use the method taught by Caterpillar.  more JMO

[71chally416]

I've always used the socket method and never had one pop out. It should fit without slop on the inside of the plug and not have sharp edges that can cut into the metal or brass. I think the sealer is more important than the installation method. I use the hardening type thick Permatex from a tube on these and NOT silicone. There might be a better method but that's always worked for me for the last 35 years. Ditto for the cam plug behind the camshaft. Also make sure the plug fits right and doesn't drive in too easily. It's a definate tight interference fit. The way things are today I wouldn't be surprised at all if there are some out of tolerance undersized Nipponese plugs in the parts system.

Like the Japanese buisnessman said to the Aerospace supplier about grade 8 bolts: "Is no problem... we can put any mark you want on bolts" 

[moper]

There's also the wide and narrow brass plugs... I use the socket method, and this was my first leak. At least I found it before the customer did.