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Idle oil pressure keeps getting lower after rebuild Hey guys, hoping I can get some help here as this is my first engine rebuild and I'm kinda stuck on what to do. I have a 1971 C-10 that I put a 5.3 LM7 with a turbo in my truck and I recently rebuilt the motor. It has all new bearings, new cam, valve springs, ls9 head gaskets, and rod bolts. Ive already rebuilt this motor once before and I'm having the same exact issue as I had before so clearly what I'm doing isn't working. When I first started the motor, I had good oil pressure (not sure what is was exactly because my gauge in the truck just says L to H) but it was most of the way up. But as I let the motor idle and drove it a little bit, oil pressure was steadily dropping at idle as well as at rpm. It has gotten so low now that I can hear the lifters clattering so I know something is definitely wrong and I will be pull the motor to investigate. What should I be looking for? I am pretty sure I installed the pickup tube correctly but have no idea if the barbell is in the rear of the motor. I never took it out but I have no idea if it's something that could fall out or if it is something that needs to be removed to put the cam bearings in. Any help would be appreciated because I don't know what to do next since I thought I did everything correctly. Thanks. |
Long shot but possibly a easy fix. There was a thread a while ago about assembly line plugging some filters. Pretty cheap and easy enough to try before pulling motor. Real pressure gauges are pretty cheap also and after having the same prob twice I'd be slapping one in for sure. |
Originally Posted by tug686spd
(Post 19878179)
Long shot but possibly a easy fix. There was a thread a while ago about assembly line plugging some filters. Pretty cheap and easy enough to try before pulling motor. Real pressure gauges are pretty cheap also and after having the same prob twice I'd be slapping one in for sure. |
Cut the oil filter open and look for bearing material or trash. |
Sounds similar to an issue from 2 months ago 1. What oil pan are you running? 2. Do you know your pickup tube clearance to the bottom of the pan? 3. Did you replace the pump during the rebuild? If so with what pump? 4. Have you attempted to restart when the engine cools? If so does it have good oil pressure then? if you were missing a pretty critical part like a galley plug you would have little to no pressure from the get go. I’m thinking your sucking air into the system due to too much pickup tube clearance or too aggressive of an oil pump vs the capacity and your sucking the pan dry. If you have flakes on your dipstick that’s not good. The only place where glitter on your dipstick is a good thing is the strip club |
It doesn't sound good. What where your rod and main bearing clearances when you assembled the engine? Is it to spec or on the lose side? What weight of oil have you been using? Could be a number of things but it sounds like you have a clearance issue and/or incurred some oil starvation and you may be going back through it again real soon. Sorry! |
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Originally Posted by 01CamaroSSTx
(Post 19878624)
It doesn't sound good. What where your rod and main bearing clearances when you assembled the engine? Is it to spec or on the lose side? What weight of oil have you been using? Could be a number of things but it sounds like you have a clearance issue and/or incurred some oil starvation and you may be going back through it again real soon. Sorry! I started the motor when cold and had very little oil pressure so immediately shut it off. I reused the factory pump, which may have been the death of me because I have no idea if the relief valves were stuck open or not. I ordered a new oil pump, pickup, and cam retainer plate hoping that that was the issue instead of a bearing clearance issue and will install if no damage is found in the motor. Not that I know much but I feel like it's unlikely to have the same symptoms I had before as far as oil pressure goes with the cause being loose bearings when I'm pretty confident they were within spec, but then again what do I know lol I'm running the factory lm7 pickup and the factory lm7 truck oil pan |
Why reuse the old pump when new ones are so inexpensive? its good insurance and peace of mind really. |
https://cimg7.ibsrv.net/gimg/ls1tech...f17a66a8d.jpeg
Originally Posted by tech@WS6store
(Post 19878740)
Why reuse the old pump when new ones are so inexpensive? its good insurance and peace of mind really. Now, I think I have some good news as to what my issue is, but maybe I am just seeing things that aren't actually there. I tore the front timing cover off and got to the oil pump today. I couldn't look straight at the relief valve but I could get pictures and it looks to me like the valve is open. Maybe someone who knows exactly what to look for could let me know if I'm right, or break the bad news that the valve is indeed closed. Thankshttps://cimg9.ibsrv.net/gimg/ls1tech...23a65171f.jpeg |
Different rod bolts distorts the shape of the big ends Since out of round it may not show up with a typical six o clock twelve o clock bearing mic job. Most likely pinching tight at the sides near the bolts and the rod bearings are relentlessly eating themselves to death |
Originally Posted by A.R. Shale Targa
(Post 19878879)
Different rod bolts distorts the shape of the big ends Since out of round it may not show up with a typical six o clock twelve o clock bearing mic job. Most likely pinching tight at the sides near the bolts and the rod bearings are relentlessly eating themselves to death |
Well, installed a new oil pump, oil pickup, and cam retainer plate on the motor today and was able to make oil pressure on the stand with just the starter. I wasn't able to make any oil pressure before with the old parts so I'm hoping that my oil pressure issue has been taken care of. Only time will tell |
Originally Posted by aruss99
(Post 19880115)
Well, installed a new oil pump, oil pickup, and cam retainer plate on the motor today and was able to make oil pressure on the stand with just the starter. I wasn't able to make any oil pressure before with the old parts so I'm hoping that my oil pressure issue has been taken care of. Only time will tell |
G Rotor Oil Pump Tech Hi Russ, your pictures are great. The material on the drain plug could be from the Oil Pump Rotors. A Rotor "side view" picture could tell BOTH inner/outer condition. The "G" rotor pump MUST ALWAYS be INSPECTED before reuse with NO wear observed. The smallest amount of wear on the rotors (sides) has a GREAT effect on pump output. SO I ASK, What method did you use to install/align the pump onto the crankshaft center ? Your report could be of great help to LS-1 tech members. Lance |
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