Date registered: Jun 2005
Vehicle: 72 250 M130 W114
Mentioned: 0 Post(s)
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RE: Setting the Timing on a '71 250
Ok. TDC, Top Dead Ceter, is when piston #1 reaches it's full compression stroke. In this situation, the valves must be closed. The piston will have reached it's apex, (the highest it can travel), The timing mark on the cam will be ligned up, and the ditributor rotor will be poiting to the spark plug that connects to cylinder 1. Typcaly this is where a running engine would fire the combustion chamber, which would follow the remaining cycles of a 4 cycle engine, power, exhaust, intake and back to compression.
TDC is determined by removing spark plug #1.
Cover the whole with your finger and turn the cam by hand. When the piston comes up and it is in the compression stroke, it will build pressure, if it does not then you're in the exhaust stroke.
It will build enough pressure to push your finger off the hole.
put a straw in the cylinder. This will help you to visualise where the piston is. As the engine turns the piston will go up and down and you'll be able to see that with the straw. makes sense?
Read the timing wheel and when it reaches 00. the straw should be at the highest point. Turning the engine any further will cause the straw to come back down.
At this point, the cam shoulde be aligned, as is in the picture, and the rotor on the distributor should be very close to the timing mark on the distributor housing. It's a little line not found anywhere else on the housing. Remove the ditributor cap.
if the cam timing wheel is not lighed up when you're at 00 and is actual at the bottom, you're at the exhaust stroke. Rotate the engine 180 degrees.
if it is off, then leave the engine, crankshaft, at 00, remove the cam wheel bolt, then the cam wheel, then put the bolt right back in there and use ut to bring the timing mark back to center.
If you have any questions, email me your phone number and a good time to call you and I will be happy to walk you through it. You can email me at ggenovez at gmail dot com.
Now if you don't mind, I also have a 250 and a haynes manual. It does not go into too many details on how to remove the rocker arm. Would you mind email me the directions on the book.
Also the ISBN # on the book would be very helpful as well.
Thanks and good luck