383-C5

Hello, this is my first post and it sucks. At first glance, you may think this is covered in another thread, but I have spent about 7 months looking all around the net (and arguing with my speed shop) trying to figure this out myself. Tonight, I decided to actually ask a question on a forum. I have had several vettes in my 49 years, and there has rarely been a time where I couldnt figure out an issue. Until the last 363 days when the C5 nightmare started. I picked up a C5 in November of 2015 that was already mildly built out. After scoping it, noticed some detonation on the pistons, so said screw it and ripped the whole thing out. New block, new rods, rings, pistons, etc. Got it back together the first week of March. Made about 575 RW on the dyno and I thought I was good to go. After a few trips around town, I noticed that my oil pressure was dipping below 5PSI when the car started getting hotter (around 220). Only happened at idle or at traffic lights. Car never showed more than 45 or 50 even when i was up in the high 2s or low 3s. Figured it could only be a few things... Oil pump, O ring on the pick up tube, sending unit, etc..... After pulling the pump (new melling), 3 O ring changes, and a new sending unit, I was still having the same problem. And I was getting low readings on a mechanical as well..... So out came the engine....Again.... Back down to the block and noticed a small discrepancy in the bearing clearance, so went an did an align hone which specked out perfectly. Put EVERYTHING back together in perfect order (this friggin project went from July 2nd through this past Friday) and put it on the road and VOILA!!!! ...............same issue... Except this time it got weirder quickly. Within one day, the pressue went straight to zero (where it currently sits)..... So I decided that we would just assume the original mechanical was a bad piece of equipment and the only other possiblity would be the instrument cluster. So........... I go get an instrument cluster and rip out the old one (today) and reinstall (today) and VOILA............. same problem.... I did forget to mention that on this second rebuild, it now has the "oil level low" warning as well... Here is what I can tell you.... The car DEFINITELY has oil pressure (makes 0 noise at 3500 rpms, no lifter, valve or other)... The car DEFINITELY is topped off with oil.... There are NO LEAKS.... It is not the oil pump, the bypass, the bearing clearance, the sending unit, the instrument cluster or anything else I can think of............. That being said, anyone with any ideas on this? I am preparing to drive it into the river (or just pretend my gauge doesnt exist)

Pounder

did you put a mechanical gauge on it ??? that would tell you right away ??

383-C5

Going to put the mech on it again tomorrow, but I cannot imagine different results. Was on the day after the last build ( last week) but I think his mech was a POS so who knows

Vetteman Jack

I'm going to move this over to the C5 Tech section in the hope that you'll get more answers to your question.