WSsick

iTrader: (13)

So my car developed a misfire on #7, did some checking and it wasn't a bad plug, bad coil, etc. Compression check yielded a whopping 12lbs on #7. Stuck a bore scope in it, piston looks ok, but it was a little tough to use. By chance, we just decided to take of the valvecover to make sure everything was ok in there. This is what we (didn't) find:





Called a few people, including a local performance shop and no one had heard of anything like this happening. So have you guys?

What could be worst case what's all damaged here? Valvetrain isn't noisy or anything, car doesn't sound like it's eating itself either. We'll do more investigation tomorrow or Friday...

RsSean

iTrader: (27)

it may have bent to the point where it fell down into where the lifter baskets are. Have you recently missed a high revving shift? Use the bore scope if it is lighted to look down in the PR hole to see if it is laying down in there.

You still have a issue with 12lbs on number 7

redtail2426

iTrader: (10)

yeah its down in with the lifters if its not up on top of the head.That would def explain your 12 lbs.If your intake valve isnt opening to let any air in then you should only get 12 lbs i would think.

WSsick

iTrader: (13)

Nope, haven't missed one in probably 4 months. When the SES light came on for the #7 mis I was cruising at 12% throttle (per the scanner) in 6th at like 60 or 65. Forgot to add this, but we are pretty sure it is in the basket. The light was running out on it, so we couldn't see **** but we are pretty sure we did see it.

defaultexistence

iTrader: (11)

good ole' non hardened PR's ...i wonder who it was that needed firing @ GM's research and development that ok'd using em...?

slopar

mine just usually eats tires and gas...

chassisbldr

The cyl will have air in it by default .. either from the exhaust side or it will pull from the crankcase past the rings .. you should see more than 12psi you probably at the very least have a stuck or bent valve

trans_am7935

iTrader: (15)

actually i have done this as well. i bent the pushrod and my dumb@$$ kept driving on it...then it broke in half completely...

kapke13

Mine did this as well. The rod was bent and I keep driving on it and then the rod blow up. I found damage on the pistons and the head.

trans_am7935

iTrader: (15)

well i hope i dont have any damage when i pull the heads, i have been running it strong for the last 20,000 miles or so, so i guess i got lucky!

BOBS99SS

iTrader: (2)

Defaultexist, I soooo agreee with ya man,good luck OP hope its just a upset stomach,

usmcz28

iTrader: (3)

If a lifter collapsed enough it would explain why the pushrod became unseated. Look in te lifter valley or the oil pany for the rest of the pieces. Only other issue would be if it shot out the valve cover but that would be too obvious.

BlackScreaminMachine

iTrader: (17)

The Pushrod is in the motor whether it be whole, bent up, or shattered to pieces. This is due to driver error over the life of the motor. Hitting the limiter excessivly can do it.

Since the valve is shut your not damaging anything BUT fuel is trying to be being shot into the cyl and no ignition. Not sure if its leaking down but ult, un burned fuel that gets past the rings gets into the oil and will wash down the cyl walls and thin out the oil. IF you need to move the car. Disconnect the spark plug wire and #7 Fuel injector incase you need to move it.

LilJayV10

iTrader: (39)

Interesting to see what you find out.

redtail2426

iTrader: (10)

I think your right.From your reply i came up with what could have happened.....Since its cylinder 7 you may have broke off a part of the piston ringland,this broken piece got itself between your piston and intake valve,causing the valve to get bent/and breaking the pushrod in the process.The bent valve causes your low 12lbs cylinder pressure,and the broken piston piece caused your missing pushrod.And the culprit to all of it was probably detonation.This has happend to peoples stock ls1's,its kinda a common problem

WSsick

iTrader: (13)

Hmm, seem to be getting a variety of answers so far. No update as of yet, haven't got to the car.

NVR_SPDS

iTrader: (39)

What I would do is to pull both rockers from that cylinder, and then do a compression check. That could rule out the valves, since both should be sealed with no pressure trying to open them.

99 Blue Bird

iTrader: (3)

i sware i didnt miss a shift either but the tare down of my motor said otherwise? or atleast thats what this would explain. i pulled my valve cover and seen the same thing. than pulled the head and found the pushrod under the lifter tray.

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WSsick

iTrader: (13)

Turns out it was the pushrod, which turned itself into 2 pieces (next to it's replacement):



Car seems to run good, but it has an exhaust leak so once that's fixed I'll be sure, but for now, 99.9% sure it's all better. Only thing I had to buy was a $2.14 magnet pen to fish it out (besides the initial diagnosis). Shop gave me a free pushrod (measured).

tdevil55

iTrader: (23)

I would recommend getting some harden push rods asap. Even though your not doing a cam swap or anything, m6 cars will benefit and the life of your LS1 will be extended by doing a PR swap. As you can tell, its not a hard process to do, and well worth the worry factor. May want to also really inspect the PR hole in the head, may have some damage to the head, it had to smack something to break.