Will L.
Well-Known Member
Yes getting the 25 psi is a pain in the... fingers. 3000 grit wet sand paper —wet so no airborn particles. I actually had a 2” deep pan with glass sheet in it. Spray glued the sandpaper to the glass and had 1” water over the sandpaper. Figure 8 sanding for getting the sealing surfaces and the spring. I did all the sealing surfaces first, got the shimming as close as possible. Then comes fine tuning by sanding the spring.
It is a monotonous, pain. I relate it to porting heads. We cheated in the shop by attaching a sheet of glass to an orbital sander with silicone. Stick on the sandpaper that was something like 800 grit if I remember right. That was done outside the clean room.
A simple note in a divider tray how much each one was over and had a chart on the wall. The d.a. sander was mounted upside down. Permanent and had a foot pedal air switch. Each pound over was like a couple seconds in the sander. Then they went back in the room after rinsing of them and your hands for the fine sanding.
I don’t remember any of the thickness= pressure stuff. That was over 20 years ago.
Everything was in metric, not sae.
I fully understand why mass production never got them close. doing the final run on an open gauge- almost impossible. Having the gauge stay on peak pressure is crucial.
Understand when I say that 25 psi- it makes a nice difference. But it is like getting all the pistons/pin/rod to weigh the same and removing the weight so the rod has same weight on top identical and bottoms identical. None of this is easy. But I don’t remember having to do that to all of them. I could swear shimming got 75-80% of them in that range. Maybe it was higher amount we did that made it easier? Maybe we had better shim selection? Maybe our springs were more consistent?
@ak diesel driver - if you test the SAME injector 40 times, are you getting exact reading every time?
It is a monotonous, pain. I relate it to porting heads. We cheated in the shop by attaching a sheet of glass to an orbital sander with silicone. Stick on the sandpaper that was something like 800 grit if I remember right. That was done outside the clean room.
A simple note in a divider tray how much each one was over and had a chart on the wall. The d.a. sander was mounted upside down. Permanent and had a foot pedal air switch. Each pound over was like a couple seconds in the sander. Then they went back in the room after rinsing of them and your hands for the fine sanding.
I don’t remember any of the thickness= pressure stuff. That was over 20 years ago.
Everything was in metric, not sae.
I fully understand why mass production never got them close. doing the final run on an open gauge- almost impossible. Having the gauge stay on peak pressure is crucial.
Understand when I say that 25 psi- it makes a nice difference. But it is like getting all the pistons/pin/rod to weigh the same and removing the weight so the rod has same weight on top identical and bottoms identical. None of this is easy. But I don’t remember having to do that to all of them. I could swear shimming got 75-80% of them in that range. Maybe it was higher amount we did that made it easier? Maybe we had better shim selection? Maybe our springs were more consistent?
@ak diesel driver - if you test the SAME injector 40 times, are you getting exact reading every time?
