Good morning all,
I have had my Tiger since February. I do not know the history of the 260
engine but the PO told me it had been rebuilt .030 over and had very few
miles on it since (take that with a large grain of salt). A recent dyno
resulted in 156 RWHP and 200 RWTQ.
I have had a constant problem with #5 cylinder fouling the spark plug. The
plug gets fouled out by black soot. It is not wet (no fuel smell) but a
thick layer of black powder. The other seven plugs look great with the
proper color for a good A/F mixture. The engine has a miss which lead me to
investigate.
I figured that it was an ignition problem with a weak spark. I have replaced
the distributer, running an Accel electronic module, replaced cap, rotor,
wires and many spark plugs. I have determined that the plug is producing a
good spark.
In the past, the cylinder produced 130 psi for a compression check while
turning over the engine.
Yesterday I did a compression check with the engine running. I started the
engine and the pressure was 60 psi. I pulled the valve cover and re-set the
valve tension (+ 1/2 turn of locking nut once all rocker to valve clearance
was out). I tuned the engine over and had 130 psi from the cylinder. I did
not check the compression with the engine running. I drove the car about 10
miles (hard) and pulled the plug..it is getting a black build up already.
I am thinking that I have a bad hydraulic lifter. My thinking is that when
just cranking the engine, the lifter operates correctly, and thus I get a
good compression number. When the engine is running the lifter is failing
and not opening the valve enough (or too much) and I then lose compression
and get a fouled plug.
I do not think it is a valve problem because I get good compression numbers
under certain conditions. If a valve or the springs were damaged, I would
never get good numbers.
What are your thoughts?
I posted the above on the SAOCA web site and got some good feedback
(http://www.sunbeamalpine.org/forum/showthread.php?t=9028). I plan on using
Marvel Mystery oil first to see if I can get a possibly gunk'd up lifter
clean. If that does not work I will pull the intake and remove and inspect
the lifters for damage. I would then replace any suspect lifters with new
ones. That or replace all of the lifters with new. I have read mixed
opinions on using new lifters on and old cam. Some say no problem others
feel that the cam needs to be replaced also. Any actual experience with
doing this out there? I am happy with the current cam's performance.
I also noticed when the valve cover was off that I have dual valve springs
(installed in 289 HiPo heads) and screw-in rocker arm studs (also a 289 HiPo
item). But, "289" is not to be found anywhere on the head. I will be
looking into this further by checking the casting numbers.
Tanks for any further advice.
Duke
B382002037LRXFE
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