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Old 04-17-2011, 03:10 PM   #1 (permalink)
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Bent Valve

Well, here we go.

I was pulling out from the Grocery store today in the Caprice that I did the LT1 swap on, I got on the throttle a little hard and it backfired and started missing bad. I'm just about tapped as far as patience goes. I swear to God it bent a f*cking valve. Rough idle, almost no power, and little bit of engine noise. I know I can do a compression and leak test. But do these symptoms sound like a bent valve to you? It's not burning crazy oil or anything. But it runs like complete shit. Possible that I just have a bent lifter?

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Old 04-18-2011, 10:42 PM   #2 (permalink)
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You can't 'bend' a lifter. Could be a broken rocker arm, could be a broken rotor under the cap.


Last edited by Gregg-O; 04-18-2011 at 10:58 PM..
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Old 04-19-2011, 12:48 PM   #3 (permalink)
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Could be a broken valve spring as well. I don't think it is very common for a stock valve spring to break(even though they are incredibly weak), or very common to bend a valve on an LT1. I would suspect other areas, before assuming it was a bent valve. It is very simple to pull the valve covers, and check the valvespring, rockers, and pushrods.

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Old 04-19-2011, 05:07 PM   #4 (permalink)
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Well I believe I overreacted. Engine noise? Well, I'm guessing it was something arcing out, or the small manifold leak just being amplified by how terrible it was running and backfiring. The incredibly terrible engine performance? The opti taking a dump. I live pretty far North, and we just got hit with some more slushy nasty snow. I believe the distributor has a crack, so water made it's way in, and caused this to happen. It was running exactly like it had a F*cked lifter, or bent valve. I have never heard of a stock LT1 do that unless it's being pushed insanely. The next morning, it started and ran perfectly fine until warm. I believe whatever water that was in the distributor had frozen over night, and after a few moments melted and caused poor performance again. I believe all problems are directly caused by the opti, and the fact that one O2 sensor is stuck at one reading. So those two things alone, in my basic LT1 knowledge, would cause crappy performance. Input anyone? I feel that I am on the right track now. Thanks guys, this LT1 stuff is a far cry from an L67 for me to diagnose.

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Old 04-19-2011, 05:09 PM   #5 (permalink)
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Quote:
Originally Posted by Gregg-O View Post
You can't 'bend' a lifter. Could be a broken rocker arm, could be a broken rotor under the cap.
I know, I tried to edit that after the post but for some reason wasn't able to. I was thinking pushrod, and somehow that came out. But I also had a thought, hydraulic lifters would make it next to impossible to bend a pushrod.

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Old 04-19-2011, 06:37 PM   #6 (permalink)
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Pushrods do get bent, but not on stock engines.

Is it setting a CEL for the stuck O2? If not unplug it and force the CEL and see if it keeps running well when warm then. Incorrect sensor feedback will make the engine run a lot worse than limp mode ignoring the bad sensor would.

Send me an email or PM about what you are planning to do about the opti.

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Old 04-19-2011, 07:28 PM   #7 (permalink)
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I will try unplugging it. Also, for some reason at idle it goes into open loop even when it's warm. I am not sure if that is normal.

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