TDC...search for the real truth
12-28-2002, 07:08 PM
#1
Instructor
Thread Starter
TDC...search for the real truth
Trying to determine the correct tdc on the compression stroke to correctly install the distributor. Have heard all the backyard ways to do it, now i want the honest to goodness no kidding way to determine. With the #1 plug pulled and the piston at the top of the cylinder what position are the valves (intake and exhaust) in when on the compression stroke? Is there another fool proof way to determine tdc on the compression stroke? Let me know, i'm dying to get the rebuilt motor started!
12-28-2002, 07:32 PM
#2
Re: TDC...search for the real truth (1972vettman)
Both valves should be closed and the timing mark at 0° should put you at TDC. Next put the distributor in so the rotor is pointing to the #1 plug wire and all should be correct.
12-28-2002, 07:34 PM
#3
Safety Car
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Re: TDC...search for the real truth (1972vettman)
Both valves will be closed. You can usually feel the compression against your finger if you hold it over the spark plug hole as you turn the engine. If there is no pressure, then it's on the exhaust stroke and the pressure is going out the exhaust valve which would be open then. Once you have located TDC, turn the engine back until the timing marks are lined up at whatever initial you want to run (engines don't run so good at 0º advance). When you install the distributor, mark the position of the number one terminal of the cap on it's housing and align the rotor with that mark. Upon start up, your timing will already be real close and you will spare yourself all the backfiring and overheating problems the 0º fans seem to enjoy :).
12-28-2002, 10:58 PM
#4
Team Owner
Re: TDC...search for the real truth (1972vettman)
If you really REALLY want to determine EXACTLY where TDC is, then you need a piston stop and a degree wheel. Put the piston stop in the plug hole. Mount the degree wheel on the damper. Turn the engine clockwise until you hit the stop. Record the angle. Turn the engine counter-clockwise until it stops, record the angle. The AVERAGE of those two angles is the TRUE TDC.
For example, suppose the piston stop stopped the engine at 10 degrees before TDC in one direction and 12 degrees after TDC in the other direction. That would tell you that your zero point isn't centered. If it was, each reading would be 11 degrees from TDC. Make sense?
For example, suppose the piston stop stopped the engine at 10 degrees before TDC in one direction and 12 degrees after TDC in the other direction. That would tell you that your zero point isn't centered. If it was, each reading would be 11 degrees from TDC. Make sense?
