C20XE Gone bad after rebuild>OIL PRESSURE

[bastiqk]

Hello!I have a very bad experience with c20xe after overhaul and full rebuild grind of crankshaft new bearings 0.25 main and rod new cambelts new seals gaskets everywhere i got just 1 very bad problem with the oil pressure.The previous engine had worn bearings and the 3rd rod came out from the block so i decided to get new block with hone and new grind crank because the old block and crank had damaged and went to recycle.After the rebuild i put oil GM 10w40 but i saw that when the engine got hot the oil pressure gets to 1 bar measured with digi and manual pressure sender the pump is same like the previous engine where i didn't had such a problem the engine was 300k with OEM bearings so it's okay to be worn after 300k but the oil pressure was staying 3 bar on hot idle 5+ when revving.Now i adapted the engine 1000km then changed the oil with Total Quartz 9000 10w50 oil grade was thinking that the oil is the problem.After more 1000km driven with that oil 10w50 grade engine had worn all the rod bearings plus main bearings but mostly the rod bearings the 4th rod next to the oil pump was hardly damaged the bearing was just the metal body everything was down in the sump.Then i said okay i will put other pump to check if the pump fail i put new bearings put the pump started the engine and same shit i just ran it for 20 kilometers then went back to the garage dissasembly everything and saw that the bearings are worn alot for 20km driven.Mostly the 4th rod bearing is worn more than the other ones i got plasti gauge i measured around 0.035mm-0.050mm clearances which is in specification i measured 3 times on rods to be sure and looks everything is okay.I'm planning to put z20LET pump but its very expensive so my questions is is it worth to put this expensive pump and if it doesn't fix my problem then im screwed again.I'm asking because i measure everything then i got again low pressure the both pumps are old but this pump worked correctly on my previous engine which fail very bad,but didn't worn bearings so hard after 300k like now after 20 km driven.I tight Main bearings to 55nm rod bearings to 45nm correct me if i'm wrong.

Every advice is welcome i'm really confused what to do and i really appreciate your help thanks in advance.

[DarrenH]

it sounds like you have done everything you can. the only thing i can think of is there is problem with crank. either it is not straight (out of round along its length) therefore bearings are strained. or the oil gallery through the middle of crank is blocked with debris from old engine failures

standard oil pump can supply more than enough pressure for your needs so i wouldn't swap to Z20 purely for that reason. you can check backlash of teeth with feeler gauge and also end float of the inner gear to casing. there is also oil pressure relief valve which you can add shim behind the spring to increase the target oil pressure.

[Vinci]

I fear something is not properly fitted making the oil exit at too much at some point, this can cause diminished oil pressure too. You could pull the crank sensor and remove a grub screw in the head in the oil gallery. Depending on the type if head where this is located, but on a ks700 head there are some under the distributor. Then just briefly crank when the engine is cold to see how long it takes to get there and how forceful it exits, it should squirt out quite powerfully. Also check if there is no air in the oil, if for instance your pickup pipe is not sealing properly this could also cause massive problems.

[Black Magic]

yes, a blocked pickup will most deffinatley cause problems. A bad regrind wont help either.

[bastiqk]

The block has been cleaned very well and stored in good conditions with oil on it.No failures before this is hone block in good conditions no problem with cylinders etc.The pickup pipe is 100% free i'm not sure about the oil gallery in the crankshaft if its something blocked,but it came from regrind and put in the car so i don't think may be blocked.I already add shims to PRV but that didn't change anything i'm going to re-measure everything to be sure for the final results then i start to dissasembly everything.I'm a bit confused about pump because i tried 2 pumps the one had worked on my previous engine and now i have low pressure and it was just staying until i put it in the new engine so i don't think that can be brake from anything.

Thanks for the advices i really appreciate them very bad that i have that problem and cant find a correct solution.

P.S. The head is Coscast checked for cracks machined everything is okay new valves new guides everything nothing bad in the head and it's not even tapping or something i don't hear any bad noise from the engine just seeing the pressure and it's lower than 2 bar at hot idle i saw lowest 1 bar on hot idle and this is alot of damage to the bearings at this pressure they touch the surfaces and fail very bad.

[DarrenH]

2 bar wont have damaged the shells at idle. it would have to be corresponding low pressure at higher revs where shock loads on the connecting roads increase

[Vinci]

I wasn't saying the pickup pipe was blocked, but rather leaking, causing it to pick up air. A failed o-ring or warping on the flange can cause that. Wrong assembly or the wrong type of bearings can also cause poor oil pressure.

[bastiqk]

Finally i found my problem "THE GRINDER GUY " didn't grind the crank correctly and it was !@#$ed up due to wrong clearances.I got new bottom end changed the crankshaft on my block i checked how the main caps are tighten originally on the new bottom end.Now watching my caps pointing at 5 main cap to the flywheel i see there is number 5 and i follow this number how it's turned and put the other main caps like that everything seem okay BUT when i put the bearings they lock on the same spot on same side not on the rotating side could this cause a problem for overturning the main bearings ? How they must lock everyone on it's side or they must be on same side one on left end one on right end ?My main caps won't fit on the other bottom end which i got already they're different blocks and different caps.It's really confusing me now after 2 rebuilds i follow the numbers of the main caps mainly on Flywheel cap because you cannot turn it otherwise so i follow other numbers to be on same side .

[bastiqk]

Everything is fitted correctly now i did the rebuild and still have the same problem with other crankshaft new bearings etc. i will try to remove the oil cooling system to increase somehow the pressure to the bearings.I'm thinking that something is wrong with the cooling system because when it opens the big circle the pressure starting to get lower and lower and when i press the gas it doesn't increase.On cold when i push the gas i get 4.5-5.0 bar maximum,but when i keep pushing on 5k rpm it's starting to get lower and lower thinking also of pressure valve,but its also cleaned and oily it's not stuck.I put washers to increase the pressure.With perfect crank and new bearings i still have the same problem and i really don't get it every gasket on the oil system is new and the oil is not bleeding anywhere i really can't understand what is going on.The block is cleaned what is possible is it possible that valve on the top of the block which is restrictor because i don't have it can it be a reason for low pressure i really don't believe this but give me your opinions.