Duke
Donation Time
Cylinder #5 saga…UPDATE 25 Jan
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.
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?
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.
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?