Timing change questions.

[bellabulldog]

Do you need to have TDC when pin timing an engine?

It is unclear to me, but shouldn't I just be able to center the tab in the pump hole so that the pump timing pin interfaces with the timing pin tooth, break pump nut loose, and then rotate engine til engine timing pin goes all the way in?

I ask because in part, my very limited understanding of engine timing, and due to lash, that if I want to retard timing on my engine, I should pin time back to stock, then advance because that corresponds with the engines natural rotation direction?

This is probably covered elsewhere and certainly someone who knows more about wrench turning could probably infer from the numerous other threads regarding timing, but I have never wrenched on a vehicle til owning my truck.

Thanks,

Andrew

 

[Redrider2911]

No need to repin the pump unless you are going back to stock. Just zero out the dial indicator when the plunger is at bottom of stroke. Then rotate engine until the cam pin slips in. What does the dial indicator read? Check that against a timing chart to find out what it's timed at.

Unpin the cam and rotate engine until dial indicator reads the lift matching your desired timing according to the timing chart. Break loose pump gear. Rotate engine until cam pin slips in. Check that your lift measurement didn't move. Tighten down pump gear. Remove cam pin. Done.

 

[Redrider2911]

You are correct in thinking about back lash. Not many people take that in to account. After you set your timing, it is always a good idea to turn the motor ccw probably about 1/4 of a turn then back forward until you can get the cam pin in again. And recheck your timing. If it is close to where you want it then you are good.

In my experience, there isn't more than .5* of lash in the gearset.

 

[jasonc]

Behind the timing case by were the pump bolts up there is a push button that goes into the cam gear for tdc. If your good with were the pumps pinned timed at install the gear there. If you want to advance timing from where its pin timed at role the engine back counter clockwise the number of degrees you want to advance pump timing then install pump gear.

 

[56cummins]

Lift charts don't always work with benched pumps. Also the pin timing could have been changed, spill port timing would be best.