fuel pressure befuddlement, huh Options

[r3dplanet]

Because I can't leave things alone, and maybe because I'm always trying to figure out the last 3% of why my 1971 1.7l engine doesn't purr exactly right, I spent some time with the Haynes manual to look things over.

I thought I had checked out the fuel pressure valve before, but I never really have. The book says (as do several knowledgeable D-Jet wizards) to set the pressure at 30psi. Mine is set to 35psi. Five pounds too much. Huh.

So I adjusted it back to 30psi and the car ran terrible. I thought there might be a change in timing and I was right, but even by re-timing the engine it still ran horrible. So I pushed it back to 35psi. Now it works.

Mostly.

But this raises a question. Why is it set so high? I nudged it up a little higher to 36 or so and it actually ran a tiny bit better. I don't like setting it so high, so I'm confused. The fuel pump isn't stock as far as I can tell. Or least it doesn't look at all like the one in the Haynes manual.

Any thoughts?