Help freeze plugs and cam plug leaking

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Lil Demon

Lil Demon

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I completely rebuilt this motor and spent some generous time repairing all the plug hole surfaces since they had ALL been marked at 3 points with a center punch likely. I first assembled the motor using the steel narrow lip freeze plugs and I applied shellac to the surface. Well I'm sure you can imagine how that worked out. So I went back and replaced all the plugs using brass plugs, again further repairing the surface but being careful not to go hog wild and risk making the hole out of round. I once again used shellac and low and behold 3 of them still weep. My rear cam plug is leaking as well. Not sure I installed it facing the right direction honestly. Any tip and suggestions welcome. I am getting frustrated with this darn motor. For the first time in my life am I considering using rubber plugs. I live in south Texas and the car would never be exposed to extreme weather. I just hate the way it would look. Thanks in advance as always!
 
Why on earth would you use shellac? It's not a sealer. It's a wood finish. You should use the right thing for the job. I always use high temp silicone RTV. I just skim a dab off of my finger all the way around each plug. Also I try to find the plugs with the thickest contact area as possible. I never use those thin plugs. They never turn out well.
 
Coat the back and use a permatex sealer and deep brass plugs. 35 years and still no issues since installing.
 
I wouldn't use shellac, regardless of who recommends it. See that description? "Economical sealant". When I am sealing something, cost is the last thing I look for. Silicone RTV will go into small holes and imperfections and seal very well. It's thick. Shellac is very thin. I've sealed some freeze plug holes that probably should have been bored over size because of pits in the circumference of the hole and without gooping it on too thick. The stuff just works. That's exactly what it's made for. That Indian Head stuff is a trip back to the 1940s. The only other product I also like with freeze plugs is Permatex #2. It also works very well. It has a pretty high maximum operating temperature, 400*. The high temp red RTV is still higher at 650*. The Indian Head shellac is only 350*.
 
OP, how are you installing the freeze plugs? If the force of installing them is concentrated near the center of the plug, it will distort them by pulling in the sides a bit and the fit will not be uniform. They need to be driven in by placing something like a socket in the plug's recess that is just a bit smaller than the pug's recess, and them driving on the socket. That keeps the forces near the plug edges.

And be aware that there are very fine size increments for freeze plugs, like increments of 1/64", which is about a .015" increment. It would be easy to get a size that was .015" or .030" on the small side, and they would install 'snug', but not be properly tight. Where are these freeze plugs coming from? Are they being looked up to be the exact proper size?

As for shellac or Form-a-Gasket #1, they are intended for sealing together tight fitting metal-to-metal surfaces, like sealing together the 2 halves of a piston aircraft engine crankcase for a pressure and oil tight seal.. or freeze plugs. So I am not 100% convinced that is the issue here. But if the holes are pitted or otherwise out of round, then it sounds like the RTV stuff will do you better. Can't hurt to try it next time.
 
Thanks for the tips and advice. I've been a auto technician for about 30 years. I own a successful large repair shop. It's my own projects that make me frustrated and short fused I guess. LOL. I have limited time to invest into my personal stuff and I want to work right the first time, hence why I used the shallow plugs since those are the ones I got with the gasket set and was short on time and chose not to drive down the street for the proper ones. As far as tooling. I do own a great freeze plug driver set and of course an assortment of modified hand tools to get into tight areas. I think I will use RTV. It's a material I seldom use unless it's on corner of intake/oil pan gaskets. Since I like to make engines seal as clean looking as possible. These holes are too deep I guess for shellac and will go ahead with RTV. I really appreciate the advice. I knew the answers. I guess I just needed a counseling session of sorts lol. I just want to drive my darn car and well fortunately I'm blessed to be busy and I love working on my personal stuff cause I'm a perfectionist, but I need to rely on my techs more and will probably get to drive my car(s) sooner. Thanks gentlemen for all the advice once again!
 
Hopefully that blessing of being super busy with work will have long term rewards, like being financially comfortable heading into retirement. I know the same frustrations..... my 'latest' rally car build stalled out 8-9 years ago!
 
nm9stheham said:
Hopefully that blessing of being super busy with work will have long term rewards, like being financially comfortable heading into retirement. I know the same frustrations..... my 'latest' rally car build stalled out 8-9 years ago!
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Yup, I feel your pain. Hopefully you can find a way to re-ignite the progress once again. You in the automotive repair industry?
 
Lil Demon said:
Yup, I feel your pain. Hopefully you can find a way to re-ignite the progress once again. You in the automotive repair industry?
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No sir.... my business is in specialty systems and equipment for cellular and public safety communications. My son is gearing up to take things over... my pending retirement is 'the writing on the wall'. We'll see if I still know how to read LOL
 
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