check out this timing piston

[turboram]

Has anyone seen one of these the one on the left is cummins the one on the right is 4cyl.

It allows for twice the timing advance over cummins, something like 20-22 degrees
I built an air pressure adapter for the case and found out it takes over 50psi to start timing advance, 90to make half, and 120 to create full advance. And if I were to shorten it a little there could be 30 deg total of timing advance If it were run without the ksb it would be easy to change out the springs for timing curve tuning

[skilletky]

is that from a VW application pump also?

[RCCUMMINS89]

Well..... we don't need near that in timing advance, not even close. BUT, if you need any spring specs.... let me know.

From personal experience, with decent fuel to need lots of timing... base timing still needs to be advanced quite a bit in order for it to come off the line correctly. On my set up, it would run the best if I had 16 at an idle and 30 at full advance. In order to get both close on both of those I run around 20 idle, which puts me grossely over advanced at about 2000-2200 at real light throttle.

The biggest issue we run into is having a spring strong enough to "hold back" the timing at mid rpm while still allowing it to move at high rpm.

[RCCUMMINS89]

We really need timing that is more in tune with the amount of throttle we are giving as opposed to just the rpms we are giving it. It works...but isn't the best option. With really big injectors we actually get punished with dropping case pressure and thus losing timing when we need it most.

[RCCUMMINS89]

If one were to add in that piston in a stock pump.... would the base timing stay the same?

What I'm wondering is if you could just swap it out and your timing curve would stay the same or similiar but it wouldn't stop it as much at full timing advance.

[BC847]

FYI: That timing piston on the left has a damping restriction device that includes a spring-loaded ball-valve for the purpose of smoothing the case pressure applied to the piston.