Bent valve?

[paulg]

So recently driving my car I got on the throttle and as soon as I let off it died. No noise or weird sound just died. Turned back on no problem. Then later it shut off as my foot was in it. Wouldn't start back up. Spark and fuel are perfect.

So i Checked all grounds reset the cam sensor (per caspers cam sensor tool) and couldn't get it in time. Yes I set it at 25* after tdc and no it's not 180* out. Car started and sounded like a tractor WTF! Air back firing through the throttle body then shut off.

So now I'm assuming the Timing chain skipped a tooth or 2. Pull off the front cover and chain looked perfect. At tdc the marks on the gears line up perfectly.

So now I think maybe I wiped the cam flat. Oil is clean so I pull off the intake to take a look no metal shards litters all look normal same swirly mark on the bottom of each lifter. So I turn the motor to see if the lifters are moving up and down (no push rods or rockers on the motor at this point) and I distinctly hear air leaking out of the DS head through #3 intake runners. Take a closer look at the valves /springs and one of #3s is sitting lower then the rest. Don't know if it's bent or broken or fell out of place yet as the head is still on the car but I'm assuming it bent.

What the hell caused this? What steps can be taken to prevent it happened again? What else should be checked out. Ect.

Ps yea I know a simple compression test would have figured this out before I took shuffle apart but it was coming apart anyway as it so happens lol

 

[TurboBuRick]

Usually when a valve is bent, it's because it got hung up and the piston smacked it. In that case you would have a dead miss on that cylinder.

 

[TurboDave]

Checked the crank sensor???

 

[SHADOWII]

For the "no start" check the fuseable links. Check the lifter to see if it cullapsed, maybe due to lack of oil via blocked oil passage or maybe a broken spring. the hiss of air from #3 could be a cracked header, which is "norm" between #3 & #5 header pipes.

 

[paulg]

I didn't check the crank sensor I just didn't mess with it when I pulled the front cover as I'm not familiar with crank sensor adjustment. I'll be reading about it on vortexbuicks right now though.

Don't think it's a cracked header as the rockers and push rods are off the car the valves should be closed. I can see the rear #3 valve/spring sitting about 8th of an inch lower then the rest. Pulling off the heads today and off to the machine shop.

My concern is to how/why this happened? My cam and lifters appear to be fine and no pushrods are bent. But should they be replaced anyway to prevent another mishap? Or was this just a really bad miss that has nothing to do with the valvetrain itself?

 

[paulg]

Doing a quick compression test right now to verify #3 is leaking.

 

[TurboBuRick]

Is the motor stock? I doubt the valve is bent. Prolly just some carbon build up. Surly not the reason your car died.

 

[paulg]

There is evidence of a rebuild. Timing chain is not the original plastic one and no tensioner on it. Warranty seals on the freeze plugs. When I pull off the heads I will look for a bore size/stamp on the top of the pistons. I'm not sure what happened. I don't remember seeing anything when I put these heads on my car but back then I assumed stuff was stock so I probably didn't try rubbing off the carbon to check at all. I'm not sure what's going on with this thing.

 

[TurboBuRick]

I was thinking carbon build up on the valve stem or a piece stuck between the valve and seat keeping it from sealing 100%.

I think you went a little too deep a little too fast.

Did you check the wheel on cam sensor? There is a tab that breaks off. When that happens the wheel is no longer keyed to the shaft. That allows for it to move around reaping havoc. Even if you set it, it can jump just by starting the motor.

 

[paulg]

I did remove the reluctor wheel in the cam sensor and verified the tab was in place so the reluctor wheel didnt spin off. I went through the cam sensor wires And cleaned the connectors etc. I did all of this the second time I reset the cam sensor.