Hey there.i was wondering if it is common to get a lower pressure reading with a smaller diameter feed line to the gauge.replaced the blown line with one of the mailhouse brands and for whatever reason,it is much smaller than the one i replaced.i read about 15 psi at idle now compared to 30 plus before.i do have the adjustable regulator on the pump also.
Be more specific, what line did you have before? The best line to use for a mechanical gauge is either the copper line or braided -4AN.
http://www.hotrodders.com/forum/oil-pressure-difference-after-changing-line-gauge-353610.html http://www.onyxvalve.com/uploads/docs/Capillary_Tubing.pdf
No, pressure is pressure. The smaller line will change how fast the gauge responds to the change in pressure. The differences noted above probably have more to do with a bad test and unknown oil temp with the readings were taken.