GT Misfire Issues

[rgartzle]

Didn’t see anything on the head of the piston, think it’s worth trying to put it back on and checking compression?

Nevermind. Ignore that. I agree with the bent valve idea

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[SheepDog]

found this rocker roller laying in the head. Assuming lifter failure, still wondering why it would have 0PSI

Maybe the valve spring broke

 

[rgartzle]

Maybe the valve spring broke

Spring is fine

 

[WildHorse]

Didn’t see anything on the head of the piston, think it’s worth trying to put it back on and checking compression?

Well you have zero psi, so something went screwy Lewie. I can't make that call cause I don't wanna be responsible if the valve is indeed bent and causes more damage.

 

[SheepDog]

If you have one of these and a compressor, you can remove the spark plug of that cylinder and then pressurize the cylinder (Compression stroke obviously). If one of the valves is bent you will hear the air rushing out the intake or exhaust depending on which valve that rocker was attached to

 

[WildHorse]

So, whatcha ya find other than the rocker ?

 

[rgartzle]

So, whatcha ya find other than the rocker ?

Nothing so far, done for the day. Thinking about sticking the borescope through the intake port if I can see anything. Problem is after I set that rocker back in place now the starter is just clicking (battery has enough voltage), so not sure what’s going on there because it’s a new starter & battery.

If I get good compression on that cylinder once I can get it to crank do you think that would suffice? Or would it still be a better idea just to take the head off and get that valve out

 

[WildHorse]

If I get good compression on that cylinder once I can get it to crank do you think that would suffice? Or would it still be a better idea just to take the head off and get that valve out

I'd do a leak down test. That way you can elimiate a bent valve(s).

 

[rgartzle]

I'd do a leak down test. That way you can elimiate a bent valve(s).

That’s next, I’ll let you know what I find. Appreciate the input so far

 

[ice445]

found this rocker roller laying in the head. Assuming lifter failure, still wondering why it would have 0PSI

Any substantial leak will lead to 0PSI compression. Did you check which side that rocker was for? intake or exhaust? I assume exhaust, since if the exhaust valves are stuck closed it will pulse air back into the intake, causing misfires on other cylinders.

 

[rgartzle]

Any substantial leak will lead to 0PSI compression. Did you check which side that rocker was for? intake or exhaust? I assume exhaust, since if the exhaust valves are stuck closed it will pulse air back into the intake, causing misfires on other cylinders.

Right side intake valve on #6

 

[rgartzle]

Well I compression tested #6 after I put the roller back in and it came back with 220psi and held so safe to say the valve is seating properly. However I did turn the motor a couple of times by hand before trying to crank it and did notice that a tiny screw ended up in the cylinder.

Not sure if might’ve wedged itself in between the valve from being dropped in when the intake manifold was installed but either way I’m assuming maybe that was holding the valve open and I was able to dislodge it. Car runs great now

 

[NGOT8R]

@rgartzle, where did the screw in the #6 cylinder come from and how did you remove it?

 

[ORRadtech]

Not to speak for the OP but my borescope came with a magnet attachment. I've been able to retrieve small things from some very tight places. A screw in a cylinder would be pretty easy.

 

[rgartzle]

@rgartzle, where did the screw in the #6 cylinder come from and how did you remove it?

I had an exentendable magnet and I just bent it a little bit, it took a few tries. Looked like a hose clamp screw

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