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post #1 of (permalink) Old 11-21-2002, 03:36 PM Thread Starter
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Need engine help!

<font color="green">Okay, before the weather turned bad over here (damn rain) I was tooling around with the Zuk. A few weeks ago I did a compression test on my GM 2.8L and only one cyl had 130psi (that was #2) the rest had around 0-35psi! So, I pulled off the valve covers and the damn rocker arms were too tight! I couldn't even turn the push rods! Would that keep the compression from going up? I checked the head bolts, and everything else and they are all tight and torqued to specs. I don't know much about engines, but I was told to get a valve job done and that would fix my problem. Just wanted to know if adjusting the rocker arms or valves would help any before I take the heads off!
Help get my monster running again, I miss it! [img]images/graemlins/frown.gif[/img] </font color>
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post #2 of (permalink) Old 11-21-2002, 03:42 PM
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Re: Need engine help!

Of course if the rockers are too tight it can lower compression. The valves will leak out compression if they are too tight, they will never close/seal all the way/correctly. You may have burned the valves if it's been run, the cam timing will also dictate the compression, if it's off by like 70* or something really odd the valves will open/close totally wrong giving incorrect compression readings.
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post #3 of (permalink) Old 11-21-2002, 03:46 PM
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Re: Need engine help!

or the intake valves would not flow air into the cylinders on the decompression stroke. Did you put a brick on the accelerator petal and remove all the other plugs before you tested the compression????
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post #4 of (permalink) Old 11-21-2002, 04:04 PM Thread Starter
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Re: Need engine help!

<font color="green">When I did the compression test, I just did what the back of the package said to do! [img]images/graemlins/confused.gif[/img] But, I don't remember putting a brick on the pedal. Would that make the test results different? I did remove all the other plugs, but no brick! </font color>
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post #5 of (permalink) Old 11-21-2002, 04:42 PM
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Re: Need engine help!

howdy,
the brick is just to give the engine more gas bringing up the compression to running speed. and i would not worry about a valve job. if the valve are to tight it will push the valves into the cyclinder let compression leak past the valves. so that when the valves are at the right tension the valve spring holds the valve up againest the head. with the valve to tight the valve sits lower and compression passes by the valve. hope this helps. i would say you need to just adjust your valves back and then redo the compression check and you should see a difference in compression.
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post #6 of (permalink) Old 11-21-2002, 04:53 PM
 
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Re: Need engine help!

The closed throttle keeps the cylinder from flowing as well as it might. Do adjust the valves
properly first, as mentioned. I'll bet the 135# cyl was too tight too.
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post #7 of (permalink) Old 11-21-2002, 04:59 PM Thread Starter
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Re: Need engine help!

<font color="green"> Thanks Jim and Outlawmws, I'll adjust the valves tomorrow and see what I get. And yes, the #2 cyl. with the 135psi was too tight as well! [img]images/graemlins/grin.gif[/img] Thanks again! </font color>
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post #8 of (permalink) Old 11-21-2002, 10:15 PM
 
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Re: Need engine help!

did it never run? why are the valves too tight to begin with? but to answer your question.....if the rockers are too tight it could cause it to not have compression. i am confused as to why all of the sudden the rockers are too tight and it won't run. [img]images/graemlins/confused.gif[/img]
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post #9 of (permalink) Old 11-22-2002, 05:55 AM Thread Starter
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Re: Need engine help!

<font color="green">Okay, it ran before but it had some oil leaking problems. So, I replaced the head gasket, valve cover gaskets, the rear main seal, harmonic (sp?) balancer was bad and now that is fixed, the oil pan gasket was replaced... So, I might of put the rocker arms in too tight? I was going by what the manual said to do, and guess that is wrong!?!?! So, I'm going to adjuest them so that I can move the push rods with my fingers, but they are going to be snug! </font color>

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post #10 of (permalink) Old 11-22-2002, 08:26 AM
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Re: Need engine help!

OK, its been a while since I did work on GM 2.8's but the lifters might had not been fully pumped up with oil, so when you tightened them down, it might have been to tight and never knew it. After you got it running and they built up pressure then they became too tight(obv) If it runs, start it up let it run for a few, and redo the rockers, dont mistake side to side play for up and down play in the rockers, as they'll still move side to side but be too tight.
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