Cobra issues... Any thoughts?

[Phish]

Last night Jordan and I came across a strange issue when working on a Cobra. To start things off, it had no compression on Cylinder seven. We are thinking the worst but decide to take a closer look. I get a borescope and look in the plug hole and everything looks grand. We want to check the valves so we pull the blower off. All intake valves look excellent. Decide to go a little deeper and check out the exhaust valves. We pull the valve cover and Jordan discovers something that we though was going to be a quick fix and have the car up and running in no time. The rocker was off the valve on the farthest exhaust valve to the back of the car.

Even with the rocker off, the spring looked to be compressed a little. We kept compressign the spring and releasing it and eventually it released and came back to normal operation. Pulled a compression check and WHAM... compression!Jordan snaps the rocker back on quick like and we compression test again. ZERO compression. Rocker off... compression like a champ. Rocker on... none what so ever.

We assume the rocker has issues from coming off and hanging out in the head for about 50 miles of driving (looks good though). So we remove the rocker off of the other exhaust valve, put it on the valve we are having issues with and leave the rocker off the new valve. No compression once again. Its not the rocker. We take off both rockers just to double check ourselves. and we have compression.

We are now getting to be pretty stumped over this. The valve seats fully and is easy to move up and down so we dont think its a bent vavle. We checked the spring out and it does not seem to be broken or cracked. Anyone have any ideas of what this could be. Obviously the head is going to have to come off and gone through. But this is just a little mind boggleing.

Let the thoughts start rolling guys...

[c_mart_28]

Weird.

I don't have any beneficial input but I'm anxious to see what people think.

BTW, this is a '03 Cobra Phish is talking about.

[slow ride]

Over rev might have caused piston to valve issues and bent the valve causing it to bind in the guide. Rocker keeps falling off as it's not loaded at times. Is the lash adjuster/lifter ok?

[Phish]

If the valve was bent then woudlnt it not seat or seal when the rocker was off the valve. Not only does it have compression but its excellent compression when the rocker is not there. Everything looks good as far as the rocker and its install goes. It fits nicely onto the valve and the oiler and there is no slop or play when its installed. Tight to the cam.

[Phish]

Here is a little pic of what we found down inside after taking the valve cover off. You can kinda see the spring/valve also.

http://i232.photobucket.com/albums/ee44/Phish806/IMAG0180.jpg

[skipdownstairs]

Im thinking perhaps the valve may be binding in the guide also. I would remove the retainer and spring and check to make sure that the valve moves perfectly freely then throw that spring in a checker to check the spring pressure something is a miss and you will find it I'm sure, just hope the head doesn't need to come off may be a bad/weak spring???

[skipdownstairs]

Only other thing that comes to mind is the lash adjuster like what slow ride said take a look at that and or put a new one in there just to be sure

[Phish]

We swaped the adjuster with the valve next to it also. It had no effect on anything so it would not be the issue either. I am thinking we can pull the spring out and see if the valve has any issues moving in the guide.

[slow ride]

Not sure what resolution that bore scope has, but check the piston over to see if it might have a slight sign of valve contact (expecially that exhaust valve location).

[Phish]

That was the issue we had with the borescope. It would only go down to the threads for the spark plugs - then the head was to big to fit (thats what she said). However, everything we could see on top of the piston looked good. We may have to take another look jsut for saftey measures.

I think Sat we are going to remove the spring and see if the valve has any issues with movement. Replace the spring if the valve checks out. We can take another look at the piston there. Hopefully we can get all this done and figured out without removing the head.

[slow ride]

Hard to say, but even if the spring was weak it wouldn't cause a problem when cranking the engine over of a compression test I'd think. Just seems like there is a valve stem to guide issue going on. I'm guessing the head will have to come off, but I hope it doesn't. Good luck with it.

[Phish]

Yeah, we should know saturday. The valve is where we will dive to first. I will try and keep everyone posted, but this seems to be the only theory that we can come up with at the moment.

[Phish]

So, Yesterday I head to Jordans to attack this car a little more. Our plan of action before heading to the garage was to remove the head and check the valve in the valve guide along with the spring. We head to the garage and just for grins we check the compression. Cylinder seven has perfect compression and cylinder 5 has NONE. So instantly we know that the last time we worked on the car, we swapped the rockers and lash adjusters between those two cylinders. Now we know it has to be one of those two things.

We run and steal an adjuster and rocker off of another motor Jordan has laying around and p0p them on cyl. 5. No compression. At this time, we are starting to get a little mind fucked. "Theologicly" we had eliminated all components that could be the issue. After a little bit of playing around with different ideas. I realize we are really retarded. We never Bled the new lash adjuster before installing it. We pull it out I bleed it and drop it back in. Turn the car over and WHAM compression.


To sum it up. The rocker came off CYl. seven. When we first found the issue and re installed it. it still did not hold compression because when driving the car with this issue the lash adjuster adjusted itself fully outward. Thus when re-installing the rocker it held the valve open the slightest amount causing the loss of compression. Once bleeding The adjuster and re-installing the rocker the problem was fixed.

That being said. Jordan, Matt and I re-installed the Valve cover, the blower, and everything else to get this trurd back together in around 45 minutes. Car fired up and ran like a champ.

We ended up taking the car to a Car meet in town and calling the owner to come to the meet. He had no clue that we had it fixed and was still thinking it was a pretty major issue. It was a pretty cool setup. He was quite surprised to see it sitting there and definitely had to do a double take on that one.

Now giving credit were credit is due, It was quite the group effort doing the work between Jordan, Matt and I. Also a few suggestions from people gave us a good direction to go in. So thanks for the help all. Glad to get it fixed, up and running and all for the price of $0.

[c_mart_28]

Well done guys.

Glad to hear it was nothing major!

[snickerlicker]

Did you blow anyone away in it??

[slow ride]

Is there any chance of piston to valve contact when the lash adjuster is fully extended? Should let them sit installed or turn the engine over by hand a few times to make sure they are not pumped up. Either way it runs now so good deal.

[Phish]

I really dont think that there was any contact in that manner. When we looked at the piston with the borescope we could not see any marks atop the piston. It all looked really good actually. When all re assembled compression was excellent. I really do think there was alot of luck involved with this not causing some major damage though.

[Batwood]

Sounds like it could have been a nightmare! Glad to see it was easily resolved. Pulling the heads on these don't appear to be much fun.

[Phish]

Yeah we were talking about pulling the head. It woudl have been a major pain. We were lucky it was on the passenger side. I dont believe the drive side valve cover can be removed with the motor in the car. So same issue on the driver side would have required pulling the motor.

[BGjohnson]

popping out the finger followers is a known issue with these things. Usually an over rev by downshifting. Glad you guys remembered to bleed the lash adjuster before tearing every apart. It was going to be my suggestion.