Did I bend a valve or mess up a piston

 
Old 12-25-2018, 05:39 PM
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Default Did I bend a valve or mess up a piston

So I had just put my head onto my newly built lsvtec and without thinking I turned the crank when the cams werent at TDC. I ran into some resistance while turning on the engine. Do you think I just ruined the engine?
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Old 12-25-2018, 08:20 PM
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Default Re: Did I bend a valve or mess up a piston

Did you push past the resistance or did you stop ???
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Old 12-26-2018, 03:55 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by JRCivic1 View Post
Did you push past the resistance or did you stop ???
I pushed past it once
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Old 12-26-2018, 04:05 AM
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Default Re: Did I bend a valve or mess up a piston

Pull the head, I strongly suspect a bent valve.
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Old 12-27-2018, 10:51 PM
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Default Re: Did I bend a valve or mess up a piston

If you need some stock replacement valves I have intake and exhaust just pm me I'll make you a good deal.
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Old 01-01-2019, 02:52 PM
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Default Re: Did I bend a valve or mess up a piston

Do compression test before jumping to removing the head. Horrible advice to just pull the head. Compression test takes 20 minutes
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Old 01-02-2019, 05:31 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by Cupajoe View Post
Do compression test before jumping to removing the head. Horrible advice to just pull the head. Compression test takes 20 minutes
If you are hitting resistance hand turning it, what kind of damage do you expect to avoid trying to compression test it with a starter cranking it over repeatedly.

If there is fear of piston to valve contact, a compression test is horrible advise in my opinion.

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Old 01-02-2019, 05:46 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by TomCat39 View Post
If you are hitting resistance hand turning it, what kind of damage do you expect to avoid trying to compression test it with a starter cranking it over repeatedly.

If there is fear of piston to valve contact, a compression test is horrible advise in my opinion.
I agree, compression test is irrelevant in this case. The fact is, the OP pushed past the resistance once, and like it or don't believe it or not, that bent at least two valves.
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Old 01-02-2019, 06:03 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by shipo View Post
I agree, compression test is irrelevant in this case. The fact is, the OP pushed past the resistance once, and like it or don't believe it or not, that bent at least two valves.
This is under the assumption the timing is correct on the engine, then do the compression test.

I agree do not do with it out of time.
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Old 01-02-2019, 06:55 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by Cupajoe View Post
This is under the assumption the timing is correct on the engine, then do the compression test.

I agree do not do with it out of time.
Once again, the OP stated he pushed past resistance when he rotated the engine (which was out of time), in this case, a compression test is moot, the head has bent valves. End of story.
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Old 01-02-2019, 12:51 PM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by Cupajoe View Post
This is under the assumption the timing is correct on the engine, then do the compression test.

I agree do not do with it out of time.
I think I know what you might be getting at.

It hasn't been made clear what kind of resistance. The head with closed cylinders (spark plugs in) and proper valve lash etc, will have resistance as the lobe pushes open valves. I'm not sure if an inexperienced hand will know the difference between valve spring resistance and valves contacting piston resistance. And depending on just how the contact is made, there might not be a solid tock of the valves and piston contacting.

Instead of compression test that requires a starter/transmission, a leak down test will let you confirm which resistance was felt.
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Old 01-03-2019, 02:19 AM
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Default Re: Did I bend a valve or mess up a piston

Sounds like OP doesn't have a clue about engine building. He should just have someone competent to check for damages.
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Old 01-03-2019, 03:33 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by TomCat39 View Post
I think I know what you might be getting at.

It hasn't been made clear what kind of resistance. The head with closed cylinders (spark plugs in) and proper valve lash etc, will have resistance as the lobe pushes open valves. I'm not sure if an inexperienced hand will know the difference between valve spring resistance and valves contacting piston resistance. And depending on just how the contact is made, there might not be a solid tock of the valves and piston contacting.

Instead of compression test that requires a starter/transmission, a leak down test will let you confirm which resistance was felt.
Sorry, not buying, that head needs to come off. The fact is, depending upon where the engine was in its's rotation when the head was bolted back on, valves cold have been bent at that point; rotating the engine further would have resulted in even more bent valves.
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Old 01-03-2019, 10:19 AM
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Default Re: Did I bend a valve or mess up a piston

Originally Posted by shipo View Post
Sorry, not buying, that head needs to come off. The fact is, depending upon where the engine was in its's rotation when the head was bolted back on, valves cold have been bent at that point; rotating the engine further would have resulted in even more bent valves.
I understand.

Your perspective is based on your knowledge and experience of being able to tell the difference of valve spring resistance and compression resistance versus valve/piston contact. Simply, you know the differences in feel and you assume the OP does too.

The other person realizes the OP may or may not know the difference. If the engine is not damaged due to OP thinking it's contact but in reality it's valve spring and compression resistance, the recommendation of pulling the head is unnecessary work.

If on the other hand, it is contact resistance, then cranking the engine is the least useful advise and may cause more damage.

My thought of leakdown may mitigate the cranking, but it also means reverse turning the motor via the cam pulley to the position just before contact. This also assumes the engine wasn't turned further than past the first resistance point. If the engine has been turned through multiple resistances, it's all a moot point and doing a leakdown on all four to confirm damage/lack of damage is still sound advice.

The key in reverse turning the engine is that you have to turn the engine clockwise by the cam shaft, not the crank shaft. This will keep tension in the proper areas of the timing belt to prevent teeth skipping. And you don't turn it fast, so hand turning if you are going to do this. Don't hook up a high powered drill and reverse crank the motor at the cam shaft, the higher speed may cause issues and allow the belt to begin bouncing.

Using a leakdown test, OP can identify if their assumption is accurate. If it's not accurate, there is no need to waste energy and time in pulling the head.

Last edited by TomCat39; 01-03-2019 at 02:43 PM. Reason: spelling correction
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Old 01-03-2019, 10:54 AM
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Default Re: Did I bend a valve or mess up a piston

Well, at this point I guess it's all moot, errr, unless the OP comes back and updates us.
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