Rocker came off

ravege

Active Member
A few weeks ago a did a WOT blast and up pipe blew off intercooler. Seemed ok once reclamped. About a week later it starts to run rough, like a miss. Plug #5 is wet and smells of gas. Replace plug, wire, had a spare module and coilpack I swapped in too. Start up and there is a clacking sound like collapsed lifter, but it didn't go away after warming up. Pull the valve cover and see this:
Rocker.JPG


Buttons on cyl 1 & 3 look ok, but if you look carefully, the remaining #5 is angled. Is this just one of those things that happen from time to time, or a symptom of a larger problem?
 
Can't give you a great answer on this but can say, you're lucky the push rod didn't fall in!! Interesting you have 6293 heads on there too.
 
Replace all the buttons. Pretty common problem when the nylon gets hard and brittle. California car maybe is why the 293 heads. They have a tube in the end exhaust ports so the air from the smog pump goes in directly behind the exhaust valves. Unusual on an 87 GN. I've seen them on older N/A V6's.
 
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............ Is this just one of those things that happen from time to time, or a symptom of a larger problem?

Yes, this is part of a larger problem, most owners do not realize the rocker setup on a stock GN was used starting in the 1960's on Buick economy V-6 engines.

You have doubled the stock GN HP and raised the RPM range and retained barely adequate rockers for just normal driving, plus they are 30 year old parts.

The build you have should take you into the high 10's, and it would be prudent to be using the much more stable and stronger roller rockers.
 
Replace all the buttons. Pretty common problem when the nylon gets hard and brittle. California car maybe is why the 293 heads. They have a tube in the end exhaust ports so the air from the smog pump goes in directly behind the exhaust valves. Unusual on an 87 GN. I've seen them on older N/A V6's.
Interesting, I didn't know they ever came on an 87. There is about 10 sets of them hanging around the shop, I'm going to take a better look at them.
 
My pushrod had fallen in when I had wiped out lobe #3. My Mustang buddy and I could not get over the simplicity of the rocker system that was on the GN. Simplicity turned to cheapness once we realized that there were no "tolerances" of the rocker to the shaft and the fact that the nylon buttons only cost a couple of dollars for a bag of 12. But some have gone pretty fast with this extremely simple, cheap and effective system.
 
Those buttons breaking are pretty common if they are original. Mine broke about 15 years ago. Now I replace them every decade or so.

Pull that pushrod out and roll it on a piece of clean glass to make sure it's not bent. Also check the sides for any gouges or stress risers in case it rubbed the head with some force.
 
6293 castings are the same as 8445's except, most do not have the bridged end water ports. Some did, namely the StageI versions. The bridged water ports don't seem to be needed but they surely don't hurt. I have had one set of stage I heads and one set of bridged port production heads, but most did not have it. On the stage I heads, the EGR passages were not drilled.
I would pull the rockers and replace all the buttons.
 
I got a replacement kit from TA and replaced all the buttons on the driver side. The kit was a bakers dozen, alas, as careful as I tried to be, some broke and I was one short of doing the passenger side. The colors were somewhat varied, white to yellow, don't know if that's an age indicator of the buttons. Bought a few from Summit and they were all consistently colored white. Also installed RJC shaft braces. Running well now, and as a bonus I finally found a pesky oil leak, one of the fuel pump block off plate bolts is gone. Looks like a PITA to get at, too.

The engine was rebuilt by the previous owner, will look through the invoice again to see if there is any mention of replacing heads. Otherwise, no idea why the 293 would be there.
 
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