Hey Guys, I just completed a carb swap on my 87 camaro with a 305. It seemed to be going great until I heard a very loud ticking. At first I thought it was detonation from incorrect timing, but after pulling the plugs i found out cylinder #7's was DESTROYED! I replaced it with a new one hoping for the best, but it still knocks/ticks and barely idles at all.
After pulling the valve cover the intake valve on cylinder 7 had a ton of free play in it, it moved up and down probably a quarter inch. The push rod is not bent either, so my question is, what broke? Is it the lifter, valve itself, or something more serious? I don't know where to go from here, any help is much appreciated guys! Thanks!

 

if you just did a carb swap only why would a valve drop or lifter collapse?
did you drop somethin down the intake manifold during the swap?

 

What broke from the plug?
If the electrode broke off, it's going to bounce around & cause problems with the piston, combustion chamber, and valves.
Checke the valve springs for breakage, same for the rocker(s). Check for cracked valve stems, or even broken valve(s).

If that's not the prob, could be collapsed lifter(s) or flat cam lobe(s), stripped // damaged, or lifting rocker studs.

Check plug wires for arcing, burnt areas. A burnt plug wire will make a tapping sound as it grounds to exhaust. Check for exhaust leaks around the head // exhaust manifold // headers. That will cause ticking sounds also.

 

Thanks for the replies, well no damage to the rockers or valve springs. The electrode could have broken off into the cylinder, the plug was pretty much destroyed when i took it out.

I put the engine at tdc and lashed the #7 intake valve. When i turn the engine over by hand it still opens and closes, goes up and down. Does this rule out a broken lifter? Or even a broken valve? I'm considering starting up the engine again to see if just lashing it back down will help

 

If you can move the valve by hand, you've GOT to have some damage to what holds the valve on it's seat. Ie broken spring or retainer, valve tip, or locks popped off.

If the valve's dropped, and been been hammered up and down by the piston, theres probably some unpleasant surprise waiting for you in the bore. Like the chunk of valve head or piston that broke the spark plug.

 

With the just the plug I was saying to myself that it would be a good idea to pull the head. With the valve issue also it seems more imperative to do so. If you have a real problem you will find it by pulling the head.
Better to find out now instead of later. Could mean a new motor then. It might be nothing but could be something wrong now and cheaper to fix it now as compared to later.

 

Best to tear it down now. If it continues to run you risk debris getting into other cyls and causing more damage. I had a chunk of exhaust valve break off on a chevy 350 in my boat. I ran it till it died trying to get back to the dock. Pieces of the valve wound up in 3 additional cyls.

I'd also remove and check the "new" carb carefully. May find the little screws that hold the throttle plates to the throttle shaft are missing..

 

Thanks for all the replies, its always appreciated! Ok, looks like its time to tear the head off and see what's going on, hopefully its not too expensive to fix

 

Pull your new no 7 plug again - has it too sustained damage? Post up pics if you can, we all love some good carnage!

 

Yep, destroyed again. When i turn the engine over by hand i can feel a TON of resistance when that cylinder is at tdc. makes me think either a valve or something is physically breaking the plug.

 

Yup
You have some debris from something in there!
Don't try to start it again.
Pullmthe head.

Hopefully you caught it before the piston cracked or valves got hammered, or the cylinder wall got gouged!!! EEK!!