Did I bend a valve?

[Tatanko]

Buddy of mine and I were working on putting a new timing belt on my Talon today and in our frustration of trying to get all the timing marks to line up (on the cam gears) the wrench slipped and we pushed too far and heard a clunk. Our suspicion is that we went too far by accident and sent an exhaust valve into a piston. If this is the case, is the valve going to be bent with just mild force from us turning a wrench?

 

[92ts1]

So, you slipped and the valve hit the piston? Usually that won't cause a problem. I would say throw it together and turn it over by hand and see how it feels.

 

[No_Skillz]

Finishing the job and starting it up will tell you more than anyone guessing.

Although I don't think you did... it takes more than that to bend a valve.

 

[slipstream808]

We didn't turn it into it per se. It actually was the tension of the valve springs that caused it to hit. We were just trying to adjust and it went and it was fast. Scared us both REALLY good.

 

[Tatanko]

Ok. Comforting to know. Slipstream808 (who was there working with me) seemed to think it would take more than that to bend a valve too but we wanted more opinions. We planned on doing a compression test before we actually allowed it to fire, especially since we needed to allow oil pressure to build first before we start it anyway.

 

[No_Skillz]

Compression test on a cold motor will probably suck, so don't get freaked out.

 

[Tatanko]

The last time we did a compression test it was cold and it came back 160 on all four cylinders. This should make for a good comparison, in my opinion. Cold vs. cold

 

[92ts1]

Truth. But before you crank it with the starter rotate the crankshaft 2 complete turns and recheck timing. That will also tell you if there is a bent valve. Also, take the plugs out when you hand crank it.

 

[slipstream808]

Plugs are out but how will this tell if we bent a valve or not? Things will sound weird?

 

[Defiant]

Do a leakdown after you finish the timing job.
If you're Hercules, you bent a valve.

 

[Tatanko]

Do a leakdown after you finish the timing job.
If you're Hercules, you bent a valve.

Slipstream is the one who did it initially and he's a lot stronger than I am, but neither of us was putting any "real" effort into turning the cam gear. It simply sprung forward a couple teeth all of the sudden because all at once we were no longer working against a valve spring.

Good to know it takes a lot of effort to bend one. Can we do the test without any of the accessories hooked up? In other words, can we just get the timing belt hooked up and do the test straight away or do we need EVERYTHING put back together? Keep in mind the front subframe is out and so is the driver's side engine mount.

 

[92ts1]

Plugs are out but how will this tell if we bent a valve or not? Things will sound weird?

When your hand cranking a motor with a ratchet/breaker bar and a socket it not only makes it easier to turn, but also if you had a bent valve and the piston caught it on the way up you would know because the crank wouldn't turn. Like someone else previously stated in another thread compression and bent valves feels the same. With the plugs in, you get compression. With the plugs out you get no compression and can tell if you hit a valve. No need to crank the motor with ignition if you THINK there is a bent valve. If you did the say curtains to your head and piston.

 

[Tatanko]

I don't know if it's just your choice of words or what but I'm not entirely sure I understand what you're saying. We got the timing belt on today and everything is lined up properly, and in trying to get the tension on the belt *just* right slipstream808 did the whole "rotate the crank 6 times" deal and everything SOUNDED normal to me. The air from the pistons moving up and down was enough to push the spark plug wires out of the hole (the spark plugs and their respective wires are just sitting in the whole because we didn't want to lose them) if that tells you anything. I still am unsure what hand cranking the motor with the spark plugs out (which we did) does to tell you about a bent valve.

 

[architechnik]

If a valve is bent, then it will be the valve stem, not really the valve head. When a valve is bent it will not easily slide up and down the valve guide, creating force against the cams or hitting the piston each time the piston comes up.

With the spark plugs removed you should get fairly consistent resistance from cranking the shaft by hand across a few rotations (there will be slight tension at each cam lobe expansion and at the peak of each piston stroke). If you do not have consistent resistance, it may be a sign of a bent valve.

Again, as others have stated, I highly doubt that you would have bent a valve from letting it touch the top of a piston just by hand. Real valve damage typically occurs while the engine is revving extremely high and the impact would be over 1,000 times the force.

 

[slipstream808]

I have cranked the motor by hand a bunch today with the plugs out. It felt normal. The resistance I felt seemed just like I always would find when you are fighting the camshafts/valvesprings. The usual easy then hard (as you are pushing some valves down) combo. No wierd sounds, no wierd resistances.

 

[Tatanko]

That makes a lot more sense, thanks for explaining. There didn't appear to be any real resistance (other than the minor ones you listed specifically) and it seemed real consistent.