Ok, somewhat off-year ( 1974 Chevy 3/4 ton truck ), but applicable to all
vehicles....my truck has had the valves tapping for some time ( had the heads
rebuilt 2-3 years ago, some 30k miles on it ), and coming back from a road
trip, it started running extremely rough. Drove another hour with it like
this and got it home ok, then it sat for 10 days before I could get to it.
Pulled the valve covers off, (because we had heard the rockers tapping at 60
mph, so I knew that they needed "some" adjustment...) and found a rocker arm
had cracked in half, on the # 5 cylinder. Rockers were extremely loose on #2
and #6 cylinders as well. I bought a replacement, did rough adjustments to
take the major play out of all the extremely loose ones, then put it all back
together...bingo, runs great, better than before the "accident". Now, my
worry...I didn't readjust the valves after the initial adjustments right
after the rebuild, and it's been like that for 2-3 years. Would those loose
rockers also have received enough stress to start them to crack as well?
Should I be concerned about them? I"ve had many Chevies for years, ( '57,
'64, '66, '71, '73, etc ) and never seen a cracked rocker arm. The truck has
125k miles on it total, so are those arms due for replacement? I bought a
spare rocker arm to keep in the glovebox, in case it decides to break another
one. Just wanted to know what some list members think about this.
Also, running the engine with a valve closed constantly, what might be the
consequences of that? I think it was the 6th valve, don't know whether that's
intake or exhaust side, but it might have been working some before the rocker
totally sheared in half. My dad's Chevy truck had lost a pushrod before, and
it bucked something fierce after that, my truck just ran rough. maybe a
sticking valve, and the new rocker might start doing the same thing? just
hoping for the best right now! I'm gonna drive it short distances for awhile,
and see how it does. Thanks for any input, Oletruckers....
'74 Chebbie running again, but worried about it...
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959