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ONEX #54 Web Site
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Date: 7-9-2013
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Number of Hours: 3.00
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Manual Reference: P01
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Brief Description: Right side push rods
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In the top of the first picture is a tool I'd made for a previous VW build to determine TDC. Turns out it has a 14mm threads and the AeroVee has 12mm threads, so I had to make a new one. The tool is made from a spark plug with the ceramic busted out. I used a piece of 1/8" ID aluminum hobby tubing and potted the aluminum sleeve into the spark plug body using epoxy putty. The first brass rod has a soldered washed to prevent the rod from dropping into the cylinder. Today I just put a little bend in the end of the rod to accomplish the same thing. Putting a very slight bend in the rod provided some low friction. To determine TDC, move the cylinder to slightly before TDC and push the rod in until it touches the piston. Near TDC is necessary because of the acute angle of the plug to the piston. If the rod goes in too far, the piston will bend the rod as it approaches TDC. Now connect an ohmmeter or simple "buzz box", one lead to the end of the rod and the other to a cylinder/case ground. As the piston moves up, there will be continuity in the circuit. As soon as the piston reaches TDC and starts down, the circuit will open. The "buzz box" is a Radio Shack 273-065A, 3-20VDC buzzer with a 9V battery. Picture #2 shows the box opened up and connected to the TDC indicator rod and the cylinder head..
After determining TDC on the compression stroke of #4 cylinder (right side aft) I used the push rod sizing tool to determine the necessary push rod length was 11.18". I cut a rod to length (10.75"), deburred and chamfered, heated the end with a propane torch, and attempted to get the tip in. Lots of pounding with a hammer and block and finally got it in, but it was not a satisfying exercise. Next I used an 8mm and 5/16 socket on each end to use as a pounding surface. The sockets rest on the flange of the tips. Heating the tube and pounding on the sockets worked much better.
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TDC indicators, 14mm top, 12mm bottom
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TDC indicator and buzz box connected
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