 Compression question, What should I do? |
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| monkeyboy |
 Jul 27 2014, 01:21 PM
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#1
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Senior Member  Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None  |
I pulled my motor out of the car to work on my Fuel Injection project.
When I pulled the motor I did a compression test. Cylinder 3 and 4 are at 115-120 PSI, and 1 and 2 are at 130 PSI. Is that difference anything to worry about? Leakdown is only 2-3 % on any cylinder. Should I yank the heads and check the deck height since I have it apart, or is this not enough to worry about on a stock 2.0? |
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| malcolm2 |
Jul 27 2014, 01:27 PM
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#2
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Advanced Member Group: Members Posts: 2,738 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States 
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You did the test with the engine out? Someone will correct me if need be, but shouldn't that test be done cranking the engine, usually in the car? Maybe I mis-read and you did the comp. test before you pulled the engine.
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| monkeyboy |
Jul 27 2014, 01:29 PM
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#3
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
I have an engine stand. An old bell housing with a starter on it. I can spin the motor out of the car.
I also had the whole induction off so there were no restrictions. |
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| euro911 |
Jul 27 2014, 01:45 PM
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#4
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,845 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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Perform a valve adjustment and a compression check again, Jim
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| monkeyboy |
Jul 27 2014, 01:47 PM
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#5
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
Mark, I took the rocker arms off. I will try it again with no valves opening.
Would 15 PSI be enough to tear off the heads if it is indeed the case? |
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| euro911 |
Jul 27 2014, 02:42 PM
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#6
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,845 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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If you have the motor out and partially disassembled, half the battle is over.
If you have the time and a little play $, pull the heads and barrels, inspect the cylinder bores and check your rod play. If the cam and lifters (and cam bearings) are OK too, you can re-ring it and lap the valves and seats (although your leak-down #s look ok). 15 #s is low though … it's only 8.5% of your highest compression reading (130 psi). I'd pump more in there to obtain a more accurate reading. You've got a little homework to do. EDIT: I think I misunderstood - were you referring to the 130 vs 115?, or using 15 # to check your leak down? 130 is 13% higher than 115 and you'd like to keep lower than 10% difference |
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| monkeyboy |
Jul 27 2014, 02:48 PM
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#7
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
QUOTE(euro911 @ Jul 27 2014, 01:42 PM)  If you have the motor out and partially disassembled, half the battle is over. If you have the time and a little play $, pull the heads and barrels, inspect the cylinder bores and check your rod play. If the cam and lifters (and cam bearings) are OK too, you can re-ring it and lap the valves and seats (although your leak-down #s look ok). 15 #s is low though … it's only 8.5% of your highest compression reading (130 psi). I'd pump more in there to obtain a more accurate reading. You've got a little homework to do. Wait. I did my compression test and got 115, 120, 130, 130. My leak down test was done at 100 psi and there was only 2-3 % leak down on any cylinder. I think I'm good there. I'm not tearing into the bottom end. I have another motor that I'll build while I drive this one. I was just wondering if the 15 psi difference in compression would be worth tearing apart the top end. |
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| euro911 |
Jul 27 2014, 03:03 PM
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#8
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,845 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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See my edited post (above)
If you're building a new motor, I wouldn't worry about it now. Let's see what you get when you re-test (IMG:style_emoticons/default/popcorn[1].gif) |
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| monkeyboy |
Jul 27 2014, 03:05 PM
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#9
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
Got it. I'll keep you posted. Thank you.
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| monkeyboy |
Jul 27 2014, 04:17 PM
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#10
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
Changed out the rocker arms and readjusted the valves. Brought everything between 125 and 130 PSI.
Thanks Mark. |
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| euro911 |
Jul 27 2014, 05:58 PM
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#11
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,845 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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