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FAQ Archives: A Ticking TF
Question:
| Dear Mr. Twist, Here is a thorny problem for you to cogitate! I have conducted extensive research and value your input. My 1955 TF 1500 is making a ticking sound, prominent at idle. It sounds like a valve lash set way too wide. Here are some observations related to this sound: 1. It occurs regularly at cam speed (I think, this is hard to tell), and is most prominent at lower rpms, such as idle. 2. It lessens as the engine warms, but is still present. With a warm engine, the intensity of the sound waxes and wanes. 3. It goes away under heavy load (such as starting away from a dead stop), and quickly returns as the load lessens. 4. It is somewhat louder as the engine decelerates after accelerating. 5. The sound is more prominent on the right side of the engine. 6. Using a screwdriver as a stethoscope, the sound seems loudest with the screwdriver held against the head just in front of #2 sparking plug and at the middle tappet cover bolt. It is not audible via screwdriver anywhere else. 7. Pulling sparking plug wires reveals that the sound goes away if #2 has no spark, and returns immediately upon returning spark to #2. 8. Compression testing reveals: (pump-up pressure, amount of time required to then decline to 100#) #1 – 160#, 12 sec.: #2 – 170#, 11 sec.: #3 – 170#, 11 sec.: #4 – 170#, 12 sec. 9. Sound persists after ensuring correct valve lash settings. 10. By decreasing valve lash setting until it is just eliminated, the sound disappears. In particular, eliminating valve lash on #3 valve (intake for #2 cylinder) eliminates the sound. 11. Observation of rocker action suggests all cam lobes functioning. 12. Inspection of rocker assembly reveals: the bushings and shaft are in good shape. The rocker pads (where they contact the valve) are pitted on #2 intake and exhaust, and #4 exhaust. #2 exhaust is particularly bad. These were then ground to present a smooth surface to the valve stem, without any resultant change in the sound. 13. Lifters removed and inspected. #1 and #8 severely worn. Inspection of cam (as best possible without actual cam removal) fails to reveal any obvious defect of the cam. New lifters installed using lots of cam lube on the cam lobes and lifter faces. This does not eliminate the sound. 14. #2 intake pushrod slightly bent (about 1/16″ out of straight). Replaced, without impact on the sound. 15. All pushrods inspected and are otherwise free of galling scraping, or cracks. Ends tight. 16. Engine rotated by hand (wrench on the front pulley bolt) until piston #2 just starting to descend, as observed through spark plug hole. A screwdriver was then used to push down on the piston, looking for any free play in the small end. None noted. Top of piston noted to be carboned up (as are the other 3, as well). 17. With rocker assembly removed, intake and exhaust valves on cyl. #2 do not wiggle back and forth. 18. I considered removing I2 and E2 valves to inspect guides, but cannot do so with engine in the car. However, looking through the springs, the guides seem intact, although adequacy of this exam is doubtful. SO!! The problem seems to be in cylinder #2. Is it a bad small end? Is it a cracked rod? Is it cam-related? I am baffled why removal of valve lash AND removal of #2 spark both relieve the sound. + + + + + + + + + + Dear TF Owner, Thank you for this comprehensive overview of your TF. Try running the engine at idle, noting the noise. Place a 0.010 feeler between the rocker and valve stem. If the noise goes away, then the problem is related to the cam/lifter/pushrod. If there is a rapping on deceleration, the problem is a loose gudgeon pin to con rod fit. We’ve learned to ALWAYS check the rods for cracks. Please let me know what you find. Safety Fast! John Twist |
