Wiped Cam Lobe? What are my options? (Page 3/7)
fishsticks MAY 20, 12:10 AM
The best time to check for timing chain slack was when the lower intake was off.

Pull a valve cover and watch the rocker of a valve that's opening/closing. Turn the crank both directions and make sure the rocker moves without any delay.
tnkgnr MAY 31, 10:37 PM
Took the timing chain cover off. Chain didn't look too stretched, but replaced it and the sprockets anyways.

It does appear that things might be 180 degrees off though. When the sprocket dots align, the distributor is pointing to the #4 wire like this:


When its at #1 TDC on the compression stroke, it looks like this:


Should I go ahead and rotate the cam around so the dots point at each other at #1 TDC, or does it even matter?
tnkgnr MAY 31, 10:57 PM
Reading elsewhere on here, it seems that the dots pointing at each other is correct for #4, and both up is correct for #1.
Notorio JUN 01, 11:54 PM

quote
Originally posted by tnkgnr:

Reading elsewhere on here, it seems that the dots pointing at each other is correct for #4, and both up is correct for #1.



Did you get a chance to try anything else for this problem? It seems like a real heart breaker
fishsticks JUN 02, 11:13 AM

quote
Originally posted by tnkgnr:

Took the timing chain cover off. Chain didn't look too stretched, but replaced it and the sprockets anyways.

It does appear that things might be 180 degrees off though. When the sprocket dots align, the distributor is pointing to the #4 wire like this:


When its at #1 TDC on the compression stroke, it looks like this:


Should I go ahead and rotate the cam around so the dots point at each other at #1 TDC, or does it even matter?



The camshaft rotates at exactly half the crankshaft speed. So if you line the dots up in one direction, it will line up the other way also if you spin the motor over.

I would put it dot to dot and set your distributor to #4. Pull the plug on #4 to make sure it's at TDC. Also check and make sure both valves are closed.

[This message has been edited by fishsticks (edited 06-02-2021).]

tnkgnr JUN 02, 10:22 PM

quote
Originally posted by Notorio:


Did you get a chance to try anything else for this problem? It seems like a real heart breaker



One step at a time - will definitely post whatever the problem was once it's found (and whether or not changing the chain did anything). Though given the condition of the timing chain/sprockets, I doubt this was it.
tnkgnr JUN 02, 10:24 PM

quote
Originally posted by fishsticks:

I would put it dot to dot and set your distributor to #4. Pull the plug on #4 to make sure it's at TDC. Also check and make sure both valves are closed.




Will air whooshing out of the #4 spark plug hole confirm its valves are closed, or does this require removing the valve covers again?
fishsticks JUN 02, 11:42 PM

quote
Originally posted by tnkgnr:


Will air whooshing out of the #4 spark plug hole confirm its valves are closed, or does this require removing the valve covers again?



Put your finger over the spark plug hole. If the motor tries to blow your finger off the hole, you're on the compression stroke, which is where you want to be.
tnkgnr JUN 05, 01:23 PM
All put back together and test drive complete. There's less bouncing back and forth on the harmonic balancer when timing, but the issue remains...sigh...

I did notice something weird though. When I went to do timing I noticed that in diagnostic mode with the engine off, it appears it is quickly pulsing the injectors. Never done that before...

[This message has been edited by tnkgnr (edited 06-05-2021).]

StreetRod4 JUN 05, 02:11 PM

quote
Originally posted by tnkgnr:

All put back together and test drive complete. There's less bouncing back and forth on the harmonic balancer when timing, but the issue remains...sigh...

I did notice something weird though. When I went to do timing I noticed that in diagnostic mode with the engine off, it appears it is quickly pulsing the injectors. Never done that before...




Is the timing mark on the balancer jumping around when it's in diagnostic mode? I had a bad pick up coil in the distributor cause that before. And are you sure the noise with the engine off isn't the iac valve?