Compared to the rest of the...
Compared to the rest of the components in your race engine, freeze plugs are a nickel-and-dime part. But poor installation practices will allow coolant leaks and major headaches.
In your racecar, a cracked block from frozen coolants in the winter isn't usually the problem. Leaking freeze plugs that dump coolant on the track, however, is. If you have a freeze plug work its way loose either from the vibrations from an engine operating at extended high-rpm levels or from occasional overheating, the coolant dump is usually right in the path of your rear tires. And a spin-out or wreck from a faulty plug is the last thing you want.
Of course, it is rare for a freeze plug to pop all the way out and dump coolant all over the racetrack. The more common problem is a slow leak that aggravates you to death. It is hardly worth pulling the engine to replace one plug, but the result is a slow coolant leak that constantly makes your car nasty.
With that in mind, here are a few tips for installing leak-free freeze plugs.
Freeze plugs can normally...
Freeze plugs can normally be bought in packs sized specifically for your engine from most automotive stores.
You generally want to avoid...
You generally want to avoid the steel plugs (left) and instead use brass freeze plugs (right). Since most racers run pure water in their cooling systems, the steel plugs can corrode and may eventually weaken and leak. Brass plugs won't corrode, but you will have to be careful on installation because they are softer and can easily be deformed. I got these from my local speed shop that supports racers.
Most packs of freeze plugs...
Most packs of freeze plugs for Chevrolet small-blocks will also include several press-in plugs for the front of the main oil galleries. These are used in stock builds but have no place in racing. Throw these out and replace them with 1/4-inch pipe plugs just like the ones used in the rear of the block.
If you need to remove an old...
If you need to remove an old set of freeze plugs, the easiest method that also won't hurt the block is to use a punch and hammer. Place the punch on the lip of the freeze plug and knock that side of the plug in to spin it in the hole. If you try to place the punch inside the cup of the plug you will just knock a hole in it. Be careful not to scar the block.
Once you get the plug spun...
Once you get the plug spun in the hole, you can use a pair of pliers to pry the plug from the block.
Remember the press-in plugs...
Remember the press-in plugs we showed you earlier? The three holes in the front of the block for the oil galleries are where they are intended. Instead of using them, tap the first portion of the galleries with a 1/4-18 npt pipe tap and plug the holes with a 1/2-18 pipe plug that you can get from most automotive or hardware stores. Make sure to use liquid thread seal to prevent leaks.
Before installing your freeze...
Before installing your freeze plugs, take a moment to make sure the holes in the block don't have any dirt or crud that will keep the plug from making a good seal. If there is any, you can usually get it out with lacquer thinner, a Scotchbrite pad, and a little effort.
For racing, you don't want...
For racing, you don't want to take any chances with a coolant leak. You can use Loctite (either red or green) to help cement the plug into place. The Loctite not only helps keep the freeze plug from working loose, it also expands to seal any scratches or gouges in the block's freeze plug bore.
There are specific ways to...
There are specific ways to install freeze plugs without warping or otherwise distorting them so that they won't leak. This is especially critical with softer brass plugs. Never hit the plugs directly with a hammer. Many professional engine builders will have punches sized specifically for the plugs, but you can do the same thing with a large socket. For Chevys a 11/8 socket is just about right. Try to drive the plug in square with the bore and just until the lip of the cup is flush with the block.
The problem with using a socket...
The problem with using a socket is it can be difficult to get a grip on it and drive the plug in nice and even. If you have a seal driver set, it makes driving freeze plugs a lot easier.
The handle on the seal driver...
The handle on the seal driver gives you better control. Use a size that completely covers the plug. Then drive the plug into the bore until the seal driver contacts the side of the bore all the way around. This ensures that the plug is the correct depth and square to the bore.
Don't forget the rear cam...
Don't forget the rear cam cover in the back of the block. This should be done before the block is on the engine stand because you won't be able to reach it once the block is bolted up. Again, use Loctite and drive the cover until it is flush with the block.
In high-performance applications where a failure can be worth big money, engine builders will often "pin" the freeze plugs to further ensure they won't come out. The process is fairly simple and you can do it yourself. Drill three holes just above the lip of each plug (on the chamfer of the plug bore in the block). Use a No. 38 bit and drill the holes on a 45-degree angle until they are approximately 0.300-inch deep. Now you can tap the holes and use button-head screws or use freeze-plug pins made specifically for this task. These pins save you the effort of having to tap each hole. Just use Loctite on the pins just like you do the plug itself.