I just had a longblock put into my car recently and have noticed the oil pressure gauge droping dramaticly low ,15psi, at times on idle and not breaking 40 psi or lower on accell. I'm about 300 miles into breaking in the motor and was of course freaked the hell out about this. At this point I'm thinking that jr is right on with the oil sending unit being the problem. Here'* a link to a topic stared at MNBC by me. The topic is still up for disscusion and any input is again appreciated.
http://www.mnbonnevilleclub.com/viewtopic.php?t=225

bump

Well I finally got the car in for the oil sending unit replacement and the symptom remains. I will have another put in tomorrow on the mechanics tab being it still doesn't seem that there is any real problem with the pressure, just the gauge. 22 idle 57 accell.

Justin, we may want to swap IP'*. Just a thought. Rule out the gauge.

I'm over 500miles now so a road trip would work depending when you want to meet. just let me know.

PM me. This weekend might work. Any time from about noon on Saturday through Sunday.

I'm so MAD righjt now. Those mechanics screwed my car. They put on the old frontcover without checking for problems and more than likely that is the problem. The pressure really is droping to 10 psi on warm idle. WTF did I pay these people for and even worse WTF should I have to pay them more?! My warranty is good only with the original installer but i don't even think it will be covered at this point. THIS SUCKS!!

Worst part is I'm sitting here with my foot broke again (military disability) so I can't even put my foot in there butt! I did use a check card, but I'm not really sure what to do right now. I'd really like to know why the other mech at this shop told me pressure was fine and it'* just the gauge. I ended up paying full cost on an oil sending unit and install and there was no issue there to begin with!

Can you report BS mechanics to the ASE?? I know you should talk to the BBB about the shop, and a lawyer about any damage to the car