want to check compression. where do i
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
want to check compression. where do i
Where do i start guys? Speical tools needed, instructions ect.. would be greatly appreciated.. Seriously considering full rebuild again, and want to test how strong my bottom end is at 155+ thousand miles.. Car only burns less than half a quart after 3k miles.. Appears strong, pulls hard at all rpm's.. just wanna get an idea of what each cylinder is pulling.. thanx :)
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
Re: want to check compression. where do i (quiksilver458)
Not that bad of a job. You'll need a compression gauge. It comes with sparkplug adapters in various sizes. Pick the one for your vette. remove one plug, screw in the adapter, attach the guage and bump the engine over a few times. Write down the cylinder # and the compression, reinstall the plug and move to the next cylinder. Don't forget to releive the presure in the guage before going on to the next.
Drifting
Joined: Feb 2000
Posts: 1,994
Likes: 0
From: Charleston, WV
Re: want to check compression. where do i (quiksilver458)
You need a compression guage and a plug socket and ratchet and whatever combination of adapters you use to change plugs. Dissable the ignition...... (pull the big wire out of the dist cap) You should also dissable the fuel pump (pull the fuse or unplug the relay). Screw the guage into the plug hole and crank the engine over 5 times. (the number of times is argued by some but most textbooks that I teach from say 5). you want the readings to be within 25% from the lowest to the highest. This is the worst case I would accept and for performance I would be a little more fussy. Look for any LOW or HIGH readings. A high reading could be carbon buildup and a low one is wear and tear. you can dertermine rings or valves by folloing with a wet test ( a teaspoon of ol in the cyl) if that brings it up it's rings .......if not it's valves.
To top it off if you have the equipment (air compressor) you can do a leakdown test. Many mechanics feel that this is better than a compression test because a compression test is also affected by cranking speed
Hope that helps :seeya
To top it off if you have the equipment (air compressor) you can do a leakdown test. Many mechanics feel that this is better than a compression test because a compression test is also affected by cranking speed
Hope that helps :seeya
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Re: want to check compression. where do i (vettmech)
what fast replies.. i can pickup one of this comp testers at like a parts store right? Im going to try and do this sometime this weekend.. thanks for the help, and i'll keep ya posted! :)
Drifting
Joined: Feb 2000
Posts: 1,994
Likes: 0
From: Charleston, WV
Re: want to check compression. where do i (quiksilver458)
Yea it's available at all parts stores....... one other thing though ....... get the kind that SCREWS into the plug hole. There are some that one must HOLD into the hole and they SUCK!!!!!... you can get cheap ones and expensive ones.......... :seeya
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Re: want to check compression. where do i (vettmech)
Yea it's available at all parts stores....... one other thing though ....... get the kind that SCREWS into the plug hole. There are some that one must HOLD into the hole and they SUCK!!!!!... you can get cheap ones and expensive ones.......... :seeya
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
Re: want to check compression. where do i (vettmech)
Yea it's available at all parts stores....... one other thing though ....... get the kind that SCREWS into the plug hole. There are some that one must HOLD into the hole and they SUCK!!!!!... you can get cheap ones and expensive ones.......... :seeya
Get the kind that replaces the plug.
Racer
Joined: Aug 2002
Posts: 432
Likes: 0
From: Lancaster CA
Re: want to check compression. where do i (Steel Blue 91)
make sure to take out all the spark pbefore you do this. if you hve a blown head gasket, the adjacent cylinder can help to hold the pressure and feed it own pressure if it has a spark plug in it.
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Melting Slicks
Joined: Nov 2000
Posts: 3,388
Likes: 1
From: X
Re: want to check compression. where do i (quiksilver458)
what fast replies.. i can pickup one of this comp testers at like a parts store right? Im going to try and do this sometime this weekend.. thanks for the help, and i'll keep ya posted! :)
Burning Brakes
Joined: Feb 2000
Posts: 824
Likes: 2
From: Camden SC
Re: want to check compression. where do i (JonM)
Vettemech has a really good recommendations especially the last two sentences.
Sounds like you would really be interested in the results of a leakdown test. This test will help determine how much air (depending on the gauge set, may give a percentage, or green yellow red scale) is getting by the rings/cylinder wall.
Some good stores, (our local NAPA loans em out) may provide BOTH leak down and compression testers. Don't ya love those guys. Since the plug is out anyway, really good for making a sound decision.
90 Corvette zf6 3 speed shocks
Sounds like you would really be interested in the results of a leakdown test. This test will help determine how much air (depending on the gauge set, may give a percentage, or green yellow red scale) is getting by the rings/cylinder wall.
Some good stores, (our local NAPA loans em out) may provide BOTH leak down and compression testers. Don't ya love those guys. Since the plug is out anyway, really good for making a sound decision.
90 Corvette zf6 3 speed shocks
Instructor
Joined: May 2001
Posts: 136
Likes: 0
From: Raleigh NC
Re: want to check compression. where do i (BAdAzZV8)
Block open the throttle body also so it can suck the air in without restriction.. And for sure remove all the plugs at the same time. That will also make it a lot easier on the starter and battery. If you have bad compression in a cylinder squirt a little oil in it and redo the test. If the compression comes back up its the rings. Real low pressure in two adjacent cylinders usually means bad head gasket between the two.
