tdc question
- richcarl32
- Posts: 28
- Joined: Fri Jun 30, 2006 3:05 pm
tdc question
on a 1978 2.0 FI , is tdc when the intake valve closes completely on cylinder one. i have obsereved the valves while i turn the bolt on the alternaotor. it does not seem that the notch is lining up with o at that point. just after the intake valve closes( comes to the top). when is tdc according to the valves. please help me.
- Marc
- Moderator
- Posts: 23741
- Joined: Thu May 23, 2002 12:01 am
The intake valve is well on its way closed by the time the piston reaches BDC, but doesn't shut completely until the piston is on its way back up...exactly how far after BDC that occurs will vary with the cam, but you'll always need to keep turning the crank for more than a quarter-turn after the intake valve shuts before it reaches TDC.
When the crank's at TDC, the front three valves on one side will be shut and the rearmost (towards the bumper) valve on that side will be open. If you find this on the right side, it's #1 that's near the firing point ("#1 TDC"); if it's on the left side, you're at #3 TDC.
When the crank's at TDC, the front three valves on one side will be shut and the rearmost (towards the bumper) valve on that side will be open. If you find this on the right side, it's #1 that's near the firing point ("#1 TDC"); if it's on the left side, you're at #3 TDC.
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- Posts: 521
- Joined: Sun Mar 11, 2001 12:01 am
The marks for TDC
Hi, they are correct. However you are dealing with two aspect of timing.
1) TDC= Top Dead Center of the Piston travel. This will only help you if you have spec's on you cam timing. Remember cam timing is half of crank timing.
2) If the firing order is 1432, this means that #1 piston and its buddy piston #3 is at top dead center. So, the cam determines if its is indeed #1 getting ready to fire. Now the accuracy of the timing mark static is for TDC of the crank. To note your timing, it will be first while assembling the engine for the first time and lining up the timing marks at the gears.
Setting you timing well be for a best running condition.
TDC should only equal #1 and #3 are TDC and from there you use the marks for a point of reference, for adjusting the cam timing (or best run condition).
If it bothers you, you can buy a stationary pointer and install it for a corrected TDC, if you have proven the mark is off.
1) TDC= Top Dead Center of the Piston travel. This will only help you if you have spec's on you cam timing. Remember cam timing is half of crank timing.
2) If the firing order is 1432, this means that #1 piston and its buddy piston #3 is at top dead center. So, the cam determines if its is indeed #1 getting ready to fire. Now the accuracy of the timing mark static is for TDC of the crank. To note your timing, it will be first while assembling the engine for the first time and lining up the timing marks at the gears.
Setting you timing well be for a best running condition.
TDC should only equal #1 and #3 are TDC and from there you use the marks for a point of reference, for adjusting the cam timing (or best run condition).
If it bothers you, you can buy a stationary pointer and install it for a corrected TDC, if you have proven the mark is off.