C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

bent push rod confirmed

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Old Jul 30, 2011 | 12:02 PM
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Default bent push rod confirmed

In my last post i was concerned about possible bent push rods in my 87- although it turned out the ones that I suspected were probably ok. When I got to #2 exhaust it was clearly bent. I think the car was over-revved.

I checked all push rods and no others were bent. 3 did bind when spinning them. I replaced all 4 push rods and rocker arms with oem replacements.

Since all push rods were out I reset "valve lash" on all using the Chev shop manual. I used recommendations from the forum about how many turns after the push rod began to spin less freely (1/2 turn extra for new and 1/3 turn for existing).

Started car and it idles fine and accelerates normally but sounds ****** under hard acceleration. No smoke. Plugs look fine. No vacuum lines left open.

Did I miss something in setting lash? I did notice the directions seem to only talk about new push rods.

Tested compression this morning and all cylinders match what they read last fall. That should rule out a bent valve (shouldn't it?).

Anything else that I should check for while I have the valve covers off?

Thanks!
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Old Jul 30, 2011 | 01:26 PM
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why would you do that much work and only replace 4?
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Old Jul 30, 2011 | 01:33 PM
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Originally Posted by oldalaskaman
why would you do that much work and only replace 4?
Cheaper than 16.
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Old Jul 30, 2011 | 01:44 PM
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but now he gets to go back in and do it right
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Old Jul 30, 2011 | 02:11 PM
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I'll assume from your helpful comments that the number of turns used after reaching zero lash is appropriate and that over-revving probably explains the bent push rod.
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Old Jul 30, 2011 | 02:41 PM
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are you missing gears? sounds ###### doesnt say much

Last edited by oldalaskaman; Jul 30, 2011 at 02:48 PM.
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Old Jul 30, 2011 | 05:50 PM
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Originally Posted by mbfan72
I'll assume from your helpful comments that the number of turns used after reaching zero lash is appropriate and that over-revving probably explains the bent push rod.
I woud have replaced the bent one and the rocker/ball. replacing all of the parts that may never fail is senseless. there are many "right" ways to do most things.

we assume the valves floated, no way to know, probably not tight valve guides.

the number of turns recommended in fsm is what I would use. In my days of building it was one full turn, and what I used. same now in my 91 fsm. not sure where the other methods came from. people who were smarter than the engineers, I reckon.

lifters should stay with the cam lobes, of course. don't know what the noise is without more info, was it being driven? what?

Last edited by stoydido; Jul 30, 2011 at 05:51 PM. Reason: spell
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Old Jul 30, 2011 | 05:55 PM
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Originally Posted by stoydido

lifters should stay with the cam lobes, of course. don't know what the noise is without more info, was it being driven? what?
The op has an 87. It's perfectly fine to mix lifters with a roller cam.
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Old Jul 30, 2011 | 09:02 PM
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Thanks all. Job is done and car sounds good. AutoX tomorrow.

Manual calls for 1 full turn but anything else that I found online called for a 1/2 turn or less. Not sure why. In the end I used 1 turn.
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Old Jul 30, 2011 | 10:30 PM
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you just impressed me with your common sense
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