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Discussion Starter · #1 ·
I have an apparently bent valve in my 1996 Integra LS. A couple of months back I posted that I had a stuck exhaust valve on this car. I knew that it was in fact an intake valve, but when I sat down at the keyboard, it came out "exhaust". I reported that the rocker arm was laying loose on top of the head, I had assumed that it must have been assembled that way, since I could find no damage to the cam or rocker arm. I had bound the rocker arm on top of the head as I was replacing the valve cover after changing the timing belt.

I had noticed that the engine was running on three when I had moved it in to change the belt, but I figured that I'd worry about the miss after I replaced the belt. After I found the stuck valve, I removed the head, removed the valve, cleaned the gunk from the stem and reassembled everything. But, the engine still had a miss. When I did a compression check, cylinder one had zero PSI, while the other three had 145-150 PSI. So, I pulled the head again.

This time I found that I had a bent intake valve on cylinder one. Had I looked at everything when I had the head off for the stuck valve, I would have probably found the bent valve! I replaced that valve and reassembled everything again. The car ran well for about 75 miles and was running well when I parked it. Next time I tried to start it, it was running crappy again! I couldn't face going into it again so soon, so I let it stand for about a month. Last night I got back to it. Found that I had good spark to all four. Then pulled the plug wires, one at a time, and found that it was again number one which was missing.

Compression test again showed zero PSI on number one. When I removed the valve cover I found a rocker arm laying loose at the number one intake valve. This is the same valve which had been bent the time before! Using a big screwdriver, I could pry that valve down, but it would not come back up. I assumed that the timing belt must have jumped a notch or so, so I turned the crank so the timing mark lined up with the mark on the cover, and then checked the alignment marks on the camshaft sprockets. They were PERFECT!

My question is, "How is my number one intake valve getting bent when the valve timing is correct"? The engine now has 270596 miles on it. Any suggestions? Thanks. Bill
 

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Sounds to me like the valve is "dropping" down into the combustion chamber basically whenever it feels like it. Thus it would be bent because the piston will make contact with it (although I would imagine that this would be audible).

If the valve is not staying connected to the rocker arm then it will fall or "drop" down into the CC, thus resulting in it getting bent.

EDIT: Maybe pull the head and replace all the valve train components for that valve (retainer, spring, valve, stem seals, etc..)
 

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When you found the bent valve, what did the seat look like? Did you check the valve guide for damage? What did the chambers look like? The injectors filthy? We need more info....as I suspect the first bent valve either affected the valve seat, or the guide is damaged, either of which could cause subsequent bending.
 

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When you said that the rocker arm was laying loose on the valve do you mean that the valve spring was compressed when the cam lobe isnt pressing down on the rocker?

What youre saying doesnt really make sense to me because if the valve was constantly open your piston would hit the bottom of the valve which in turn a couple of things would happen... your piston would have been scored, you would hear an audible knocking noise and you wouldnt be able to pry down the valve with a screw driver since your valve was already open?

Please be more thorough with the details.

When you pull off the head again you might want to take it to a machine shop and have them put new guides in and check the valve seats and the entire moving assembly of the head.
 

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Discussion Starter · #5 ·
The valve appeared to be ever so slightly open, with the rocker arm lying on the head. It would follow from there being zero compression that at least one valve was partially open. I was able to pry the valve down a small amount but it did not return. The valve spring looks good, but I will measure it before I reinstall anything. I have been leaning toward a bad guide, because somehow the valve has to be partially open if it is to be hit by the piston. When I had the first bent stem here, I checked the top of the piston and could not find any point where there had been contact. Bill
 

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When you put a new valve in, you should test the motion to see if it gets stuck anywhere. If it does, that's reason for concern. I also suspect a bad valve guide if the rocker arm keeps coming loose. It seems to me like the valve is seated initially, then gets pressed down by the cam/rocker assembly. Valve gets stuck b/c of bad guide and then rocker loses tension once the cam profile is finished for that particular cycle of the motor. Then, the rocker is free to move anywhere at that point. Since this has happened more than once, my guess is the guides.
 

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Discussion Starter · #8 ·
TurboLS on Jan/14/10 said:
When you put a new valve in, you should test the motion to see if it gets stuck anywhere. If it does, that's reason for concern. I also suspect a bad valve guide if the rocker arm keeps coming loose. It seems to me like the valve is seated initially, then gets pressed down by the cam/rocker assembly. Valve gets stuck b/c of bad guide and then rocker loses tension once the cam profile is finished for that particular cycle of the motor. Then, the rocker is free to move anywhere at that point. Since this has happened more than once, my guess is the guides.
When I had put the new valve in, it slid in easily and did not seem to have excess slop. I did not try moving it up and down repeatedly. But, something is obviously wrong and the guides seem like the logical place to start. Thanks all for your input. Bill
 

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hello, i know its been awhile, but was scrolling thru threads, and i have the exact same problem with my 91 acura integra, i have 2 stuck valves, and found the arms lying on the head, i havent removed head yet, but did you figure out the issue/cause ? timing belt good,,,marks are aligned...thanks alot i appreciate it...
 
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