Build your own instrument to find

Top Dead Center accurately

 I had a need to find TDC on number 4 cylinder and remembered someone mentioned a whistle being used. Don't have a whistle, but made up a simple fitting from an old sparkplug housing, attached clear tubing and ran it into a jar of water. Bubbles came out on compression, stopped at TDC and started sucking up water immediately after TDC. I worked the crank back and forth slightly a couple times to get accurately centered. Easy to see the water level position inside the small tubing.
 

 

 

From: JWL Sent: 7/3/2002 11:23 PM
If your engine has an accurate TDC indicated for #1 some temporary marks can be added at 90 degree locations (3 added marks) so TDC can be found on any cylinder.

From: fitts Sent: 7/4/2002 1:16 AM
Great idea! Suggest using light oil, rather than water, though.

From: ole Sent: 7/4/2002 1:49 PM
GREAT IDEA, RAY! This finding of #1 TDC on the un-marked 'assembled' flathead has been discussed in the past, with no real viable solution. You have found one! (The sound of my hand smacking against my forehead- "Why didn't I..). As mentioned, oil (ATF) would be good for visual (plus, if you roll 'er too far, better to have oil in the hole). Roll 'er past TDC to pull some fluid into the tubing, mark the position of the fluid on the tube and mark the pulley, then roll er the opposite way til fluid is brought to the same mark, then mark the pulley again. Divide the distance between the two pulley marks and you've found exact TDC. BRILLIANT! JWL's mention of the 90 degree marks is right on also. Just roll the motor in the correct direction, and the firing order can be followed for TDC of every cylinder. I always mark my pulleys this way to simplify valve adjustments, etc. Again, an EXCELLENT idea... rodnut

From: rumbleseat Sent: 7/4/2002 7:42 PM
SUPER SOLUTION! This is a great method to detemine TDC. I've used the whistle type, and they weren't all that accurate in my opinion. A friend has one (I think it's a Ford item) that lights when it touches the piston (the probe is bent 90 degrees to reach the plug). When piston touches probe, it provides a ground for the light. Simple. But I still think your method is far superior and more accurate than anything I've tried. Last time I had the head off I used a dial indicator on #1 to locateTDC. Made a pointer that attaches to the timing cover bolts. Filed a TDC notch on the pulley. I also filed a few notches at 2 degree intervals each direction (both advance and retard) so I can use a timing light to check where to set the advance. Your idea is great and simple..... just like a flathead..... rumble seat