Team Chevelle banner
  • Hey everyone! Enter your ride HERE to be a part May's Ride of the Month Challenge!

Status
Not open for further replies.
1 - 7 of 7 Posts

·
Registered
Joined
·
43 Posts
Discussion Starter · #1 ·
how do you do a comprression test and what are good numbers and what are bad numbers?if they are low what types of things could this mean other than piston rings.
 

·
Premium Member
Joined
·
1,651 Posts
Warm up the engine fully. Remove the spark plugs. Block open the throttle - don't forget to close it when you are done testing! Screw the compression gauge fitting into the spark plug hole. Crank over the engine with the starter. I like to go at least 4 complete engine revolutions, but you can just stop once the needle on the compression gauge stops rising. Record the compression value. Now take a reading in each of the other cylinders. The lowest should be 75% of the highest. If it is good! If not, you need to look for a blown headgasket, bad valves, bad cam lobe.......

If you put some oil in your lowest cylinder and the compression goes up significantly, then it is the rings. If it remains the same, it's one of the other things previously mentioned.

Mike
 

·
Registered
Joined
·
3 Posts
also, before you start the car, make sure to disable the ignition. get the readys. the amount should be 75% of the highest amount. then you can do a wet test which is putting oil in to the cylinder than getting a reading. if the number is higher then what is was when its dry, then its your piston rings. if the number is lower or stays the same, it could be your head gasket or your valves may need adjustment.
 

·
Registered
Joined
·
43 Posts
Discussion Starter · #4 ·
whats the best way to block the throttle open?also how should i disable the ignition and then turn it over??

[This message has been edited by dumbguy (edited 09-10-2001).]
 

·
Premium Member
Joined
·
1,651 Posts
Get a piece of bailing wire to hold the throttle open.

To disable the ignition, ground the coil wire (the one that goes to the center of the distributor cap).
 

·
Registered
Joined
·
80 Posts
adamlym:you have to crank it over not just bump it.unclepennybags does it four engine revolutions.i just watch the gage to obtain the highest reading within a few seconds then stop
 
1 - 7 of 7 Posts
Status
Not open for further replies.
Top