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Newbie Forum: Beginner/newbie/general DSM modification questions. First mods, how to run 10's when you haven't run 12's yet, any tech question that doesn't fit in another tech forum. Probationary Members must limit their tech posts to this forum and sub-forums.

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Old 05-25-2010, 08:45 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #1 (permalink)
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1G-specific

Bent valves?how can I tell


Is there a way I can tell if my valves are bent with out taking my head off...I kno one piston and/or rings are bad but I still gotta be able to possibly drive it 15 miles to the shop so I don't want to take the head off... Any suggestions?


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Old 05-25-2010, 09:02 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #2 (permalink)
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compression test! check the compression and see a bent valve will leave the compression very low or at 0!

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Old 05-25-2010, 09:37 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #3 (permalink)
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Like I said I have a bad piston so I know there's bad compression in that cylinder....is there any other way?

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Old 05-25-2010, 10:04 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #4 (permalink)
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Quote:
Originally Posted by 90tsiawdturbo View Post
Like I said I have a bad piston so I know there's bad compression in that cylinder....is there any other way?
just about every time you bend a valve - even if your saying your pistons are bad - it still should have compression even if its low ------ with a bent valve you will have zero compression --------a compression check is basicly the only way of telling short of pulling the head and getting a shop to check it - zero compression is a sure tell sign of a bent valve also if you have a very severe miss ....even at idle --and loss of power --- but run a compression check sure fire way

Last edited by woomer; 05-25-2010 at 10:06 PM. Reason: forgot something

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Old 05-25-2010, 10:08 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #5 (permalink)
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I agree, you need to run a compression test. If you do infact have a bent valve the cylinder should be at 0 compression when testing. Read the Vfaq if you do not know how to do the test.


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Old 05-25-2010, 10:15 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #6 (permalink)
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Pull the valve cover and look for loose rocker arms. Do a leakdown test.

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Old 05-25-2010, 11:26 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #7 (permalink)
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Ok thank you guys very much for the help I appreciate it a lot!!

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Old 05-26-2010, 04:27 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #8 (permalink)
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A compression test is good but it just shows that a problem exists. Do a leak down test so you can pinpoint the exact source of the compression loss. You say one piston and/or ring is bad. You may have more than one problem. You could have 0 compression from a bent intake and/or exhaust valve and then on top of that have a bad ring in that same cylinder. A compression test won't pinpoint that. It's best to do both test.


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Old 05-26-2010, 08:46 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #9 (permalink)
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Well I'm showing low compression in that cylinder not zero compression

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Old 05-26-2010, 08:52 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #10 (permalink)
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then the valve could just be a little bent, but not bad bent....

this is bad bent....
How to change Valve guides In a 4G63T head

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Old 05-26-2010, 09:45 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #11 (permalink)
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The only way to know for certain what it wrong is to do a leak down test.


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Old 05-26-2010, 11:06 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #12 (permalink)
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Quote:
Originally Posted by 90tsiawdturbo View Post
Is there a way I can tell if my valves are bent with out taking my head off...I kno one piston and/or rings are bad but I still gotta be able to possibly drive it 15 miles to the shop so I don't want to take the head off... Any suggestions?
Pull the valve cover. If any of the lifters seem to be out further than normal, or if any of the rockers are loose you have bent valves on that cylinder.




But again, if you have obscenely low compression on any cylinder chances are you have at least one bent valve. If even one valve is not sealing properly, it will result in "0" compression for that cylinder. While rebuilding a buddy's 1G a while ago, he had two cracked exhaust valve guides on cylinder 1 which resulted in "0" compression....the valves were not even bent.


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Old 05-26-2010, 11:20 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #13 (permalink)
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Ok thanks guys!! Don't know what i'd do without you all!!

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