Mike Armstrong
Bronze Level Sponsor
I always wondered how accurate my 33 year old damper and pointer could be. To me, finding true (I like to be exacting) TDC was a PITA. The #1 cylinder plug hole angle made using a piston stop a guessing game, same with bump turning the engine using the starter till my finger blew off the plug hole. I wished I had marked true TDC when I had the heads off.
Anyhoo, I had forgotten about that dusty borescope I had hanging on the wall, the one I used to scope a cylinder that I was 100% sure a valve cover screw had dropped into via an open plug hole (I was wrong, thank God). So I pulled #1 plug, disconnected the coil, slid in the borescope, turned off the lights and was able to rotate the engine by hand using the fan blades. This allowed me to see exactly when the #1 piston reached the very top of the cylinder (kinda cool to rotate through full cycle and see the valves and piston moving ). This allowed me to see exactly where the pointer was lining up on the damper marks. Low and behold (or not surprisingly) it was off, by ‘perhaps’ several degrees.
https://photos.app.goo.gl/GQbypkSfYo8MgLSN6
The first photo of the damper is just for clearly showing the timing marks. The second is of the borescope. The third is to show where the pointer ended up when exactly at TDC (the yellow mark is 10 DBTDC and the red mark is 12 DBTDC). The pointer looks to be ‘after’ TDC, by how many degrees?
Anyhoo, I had forgotten about that dusty borescope I had hanging on the wall, the one I used to scope a cylinder that I was 100% sure a valve cover screw had dropped into via an open plug hole (I was wrong, thank God). So I pulled #1 plug, disconnected the coil, slid in the borescope, turned off the lights and was able to rotate the engine by hand using the fan blades. This allowed me to see exactly when the #1 piston reached the very top of the cylinder (kinda cool to rotate through full cycle and see the valves and piston moving ). This allowed me to see exactly where the pointer was lining up on the damper marks. Low and behold (or not surprisingly) it was off, by ‘perhaps’ several degrees.
https://photos.app.goo.gl/GQbypkSfYo8MgLSN6
The first photo of the damper is just for clearly showing the timing marks. The second is of the borescope. The third is to show where the pointer ended up when exactly at TDC (the yellow mark is 10 DBTDC and the red mark is 12 DBTDC). The pointer looks to be ‘after’ TDC, by how many degrees?
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