Cam Timing Puzzler
02-04-2006, 07:15 PM
#1
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Cam Timing Puzzler
Hey All;
Here's a good puzzle for everyone, especially those familiar with 4-valvers. The car in question is a 944S and this is how you physically line up the cams to get approximate cam timing.
The left arrows point to the two alignment "bumps" on the cam. They are supposed to point up. There is also a measurement taken between them, and a number of chain links between the two gear teeth pointing straight up. The right arrows point to the cam lobes for cylinder #1 that should be in this relative position. Everything here is correct as per the FSM.
Here is pic of a 944S cam gear that George B. sent me. Note the 12 o'clock position of the keyway, and the timing mark at 4 o'clock.
Here is the gear off of the car. Note the keyway at 12 o'clock and the timing mark at 10 o'clock.
Note the highlighted part number, which is correct according to PET.
With the cams lined up as per above, here is where the timing mark sits when the gear is installed on the key.
Questions; how do you use a gear with a timing mark 180 degrees out of phase? Where did this gear come from? Answers; no one has any clue what the H&%$ this thing is or where it came from!!! No one I have surveyed has ever seen a gear like that on a 4-cylinder car. The 944 experts are stumped.
Here's a good puzzle for everyone, especially those familiar with 4-valvers. The car in question is a 944S and this is how you physically line up the cams to get approximate cam timing.
The left arrows point to the two alignment "bumps" on the cam. They are supposed to point up. There is also a measurement taken between them, and a number of chain links between the two gear teeth pointing straight up. The right arrows point to the cam lobes for cylinder #1 that should be in this relative position. Everything here is correct as per the FSM.
Here is pic of a 944S cam gear that George B. sent me. Note the 12 o'clock position of the keyway, and the timing mark at 4 o'clock.
Here is the gear off of the car. Note the keyway at 12 o'clock and the timing mark at 10 o'clock.
Note the highlighted part number, which is correct according to PET.With the cams lined up as per above, here is where the timing mark sits when the gear is installed on the key.
Questions; how do you use a gear with a timing mark 180 degrees out of phase? Where did this gear come from? Answers; no one has any clue what the H&%$ this thing is or where it came from!!! No one I have surveyed has ever seen a gear like that on a 4-cylinder car. The 944 experts are stumped.
02-04-2006, 07:58 PM
#2
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Originally Posted by RedlineMan
Questions; how do you use a gear with a timing mark 180 degrees out of phase? Where did this gear come from? Answers; no one has any clue what the H&%$ this thing is or where it came from!!! No one I have surveyed has ever seen a gear like that on a 4-cylinder car. The 944 experts are stumped.
02-04-2006, 08:19 PM
#4
Three Wheelin'
PS, turning the crank over 360 degrees turns the cam over 180 degrees, so as long as the "cam sensor feeder wheel" behind the cam pulley is keyed in the way the cam pulley is (they match), it wont matter if you install 180 degrees off, the engine will run like before.
If you screw that up, you will get fuel injected at the wrong time, but the motor will still run fine. Individual cylinder knock detection will also be screwed up, but I cant think of any other consequences.
If you screw that up, you will get fuel injected at the wrong time, but the motor will still run fine. Individual cylinder knock detection will also be screwed up, but I cant think of any other consequences.
02-04-2006, 11:31 PM
#5
Three Wheelin'
Join Date: Jul 2001
Location: San Francisco, CA Porsche: '92 968 Blk/Cashmere
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Originally Posted by mark944turbo
I think the one w the holes in it is a 968 wheel.
