Jump to content

Compression check


Erndog

Recommended Posts

I want to do a compression check on an Olds 230 that sat for over 35 years. It still has oil in it, but I am concerned that all of the bearing surfaces are dry by now. I don't know how many revolutions it takes to get oil to the bearings throughout the engine.

Is it safe to do a compression check on it, or will those few revolutions be enough to destroy the bearings?

Link to comment
Share on other sites

Change the oil first. Then squirt about 1 tablespoon of MMO or ATF into each cylinder and let it sit for about a week. This may help prevent broken rings if they are stuck. Next, pull the center wire from the distributor to prevent ignition, although it is not likely to happen. Let it crank for about 30 seconds and you should be OK. Even on a running vehicle, you always need a bit of oil in the jugs before running a compression test.

Link to comment
Share on other sites

A common practice on rebuilds of newer engines is spinning the oil pump with a drill motor and pressurizing the system before initial startup, this assures that everything is lubricated and the oil flow will start right away. They even sell tools for this purpose that fit in the distributor opening and engage the oil pump drive. I'm not sure how this is done in your engine but may be an option if you can access the drive shaft.

Link to comment
Share on other sites

If you can turn it over by hand then first remove the plugs and turn it through a full cycle by hand, in other words make sure that all of the cylinders have gone though all four strokes; this way you should be able to detect any tight spots or binding.

Having done this then spin it over with the starter ( plugs still removed ) until you observe oil pressure on the guage or warning light.

As mentioned above you are likely to encounter stuck rings or valves after all this time so upper cylinder lube and a gentle hand are required.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...