One thought. I had a similar occurrence on an MG after getting a valve job,
including new valves, guides and springs. The rockers kept breaking. Turns
out the valves were not properly ground into the seat far enough, and when
the valves were adjusted for tolerances it caused the valve spring to bind
before the rocker and rods had finished their travel. The rockers being the
weak point finally gave up the ghost after a few hours of driving.
Pull the plugs out, remove the rocker cover and turn the engine over by
hand, look at each of the springs to see if there is still a bit of space
between the coils with each valve full open (down).
Also did you check your valve clearance before starting the car? If it was
too tight it could have easily been the cause of the backfiring and the
broken rocker arms.
Keith Meinhold
66 Marston Avenue
San Francisco CA 94112
4 1 5 5 8 5 5 9 9 8 H
4 1 5 2 5 4 9 9 0 8 C
www.navyboy.com
email: keith@navyboy.com
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
Behalf Of Mark Anderton
Sent: Monday, May 05, 2003 11:02 AM
To: Lawrence Brown; 6pack@autox.team.net
Subject: Re: broken rockers,bent pushrods
Larry,
The response thread seemed to deal more with valve adjustment than with your
original calamity. If you are breaking rocker arms and bending pushrods, I
would suspect binding valves. Since you don't know the history of the
rebuild, it's possible the valve guides were not properly installed and do
not have adequate clearance - or maybe after 10 years of sitting, they are
just bound up. Another possibility is cam timing that is far enough off
that you are getting interference between pistons and valves. Not sure if
that's possible on this engine. Given what you said, I think you can count
on having to remove the head to look for damage and to determine the
condition of the head overall.
Mark Anderton
72 TR6
Virginia Beach
----- Original Message -----
From: "Lawrence Brown" <larryandrobin@charter.net>
To: <6pack@autox.team.net>
Sent: Sunday, May 04, 2003 7:36 PM
Subject: broken rockers,bent pushrods
> Hello Listers,
> I have a '74 TR6 that I've been trying to wake from a 10 year stalled
> restoration. The previous owner said the engine had been rebuilt, and it
> appears so. After cleaning out the entire fuel system and carbs of
jellied
> gasoline I got it running, not great, with a few backfires. Oil pressure
100
> lbs., which came down to about 60 in 10 minutes. When I went to start it
> again today, there was valve clatter immediately, and I shut it down. I
have
> 2 broken rocker arms and at least 4 severly bent pushrods. Can anybody
tell
> me what happened? Can 3 or 4 backfires damage the valve gear so badly?
Do
> you suspect the oil feed to the rocker shaft? Can carburation or timing
> errors cause this?
> Any ideas would be greatly appreciated. I've done over 100 separate
jobs
> to this car, and have yet to ride one block. Its getting depressing.
>
> Larry Brown
> Asheville,NC
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