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Discussion Starter · #1 ·
I have a 72 elku with 454 performance engine. When engine was built it maintained 50 lbs oil pressure. After breaking it in and spinning wheels and shifting gears for a couple weeks oil pressure dropped about 10 lbs at idle. I changed oil to 10w 30 (wrong oil) and motor would idle at 40. Couple of weeks running it kind of hard it is idling 15 psi at 900 rpm. When driving at 2000 rpm it will hold at 50 and at 2500 it is always 60 and never fluctuates. When you let off gas it drops quickly to around 10 or less when holding the brake. Changed to 20-50 oil and it pressure is up about 20 psi on idle. Why did it change that much in 400-500 miles. Why wouldpressure dropsical much when slowind down but never change at mid speeds.
 

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Sounds like the bearing were on the tight side when built, and now they are breaking in. Your oil pressure will drop as the engine breaks in
 

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Are you reading an OEM oil pressure guage or an aftermarket performance one ? Castrol VR1 or Mobil 1 15w50 or something similar would be helpful. Take a sample of your oil and analyze it for metallic particles. Some speed shops are able to determine if you are losing the bottom end before it happens just by testing the oil that comes out of it.
 

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you have some oil clearance opening up too much and the oil pump cant keep up at idle.something is too loose or is going wrong. the 454 in my duelly has 50 at idle and 65/70 at freeway speeds and has 140,000 miles and all i use is 20/50. cut open the oil filter and see if you have any metal in the filter. did you change the filter after you broke in the cam?
 

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Discussion Starter · #6 ·
Thanks for your insight. I did change filter it is hydraylic roller cam. I will cut filter open. I am using Vavaline oil. Had engine built last year soon after that spun a rod bearing. Built it again and now with very low idle pressure I think i am losing another bearing, did buy new crank. Thanks:dontknow:
 

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Did the builder plastigage the bearings. Sounds like the bearings were a little on the loose side of tolerances and now that the motor is breaking in, they are loose enough that the motor won't hold pressure. Oil will not fix the issue since it sounds like it is mechanical!!!
suks2bu37:nanawrench:
 

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take it all apart have the big end of the rods checked ,the crank miked,and replace the cam bearings replaced.its easy to wipe out a cam bearing and not notice it and a bad cam bearing will kill your low speed oil pressure.if one was nicked during cam install or if any metal from the failed rod bearing got into the cam jurnals it will only get worse.you said you rebuilt it again after the rod failure did you send the block out to be hot tanked again to make sure there was no metal stuck behind any cam bearings?there are groves in the cam bore where metal and debris can get lodged in.big blocks will eat themselves up quick if any little thing is wrong.have the crank heat treated and cross drilled.that will help the crank and bearings last longer.
 

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Discussion Starter · #9 ·
Pulled engine can't really find anything wrong. I will change oil pump and let you know results. I am giad I pulled engine the tip came loose on hardened tip fuel on pump rod. Damaged cam shaft not sure if I can reuse it.
 

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if it scared the pump lobe i wouldnt reuse without regrinding the pump lobe.it will only get worse.i always use the stock rod to avoid this failure. on a small block there is a plug in the hole they bore for the oil to go to the filter if it is out the oil pressure will be low check to see if big blocks are the same.what pump did you use? i use the melling m77hv or the miladon hv pump. plastigauge every rod and main bearing when you put it back togeather. do it dry i have seen guys do it wet and it comes out wrong.
 

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do you know if they replaced the cam bearings? i just overhauled the motor in one of my 72 mavericks, (got in a hurry) (i said just, it's been six months)after around 5000 miles, oil pressure at startup was over 50 pounds, let it run twenty minutes and it was around 8 pounds, a teardown found nothing wrong, everything plastigauged right, so i went through the build in my head, till i realized i just put 3000 bucks into an engine and did not change cam bearings while it was in the machine shop, two days later and a new set of gaskets(and cam bearings) she maintains 40 pounds of pressure at idle all day long.
 

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Another item that could affect oil pressure is the plunger in the relief/regulator valve in the oil pump. Some aftermarket pumps, from a brand I wont name, have had trouble with the plunger, because of the bore being rough, and the plunger not seating correctly, and by-passing some oil. Honing the bore solves the problem, from what I've heard.
Just another thing to check out......
 

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It can also be as simple as where you take the pressure measurement from, If you take ot just above the filter and get those numbers---thats bad but if you are using the port by the distributor, it may not be so bad. the lower port if just after the pump and before all the bearings get oiled, the port at the top of the engine is the pressure that is left after all the leaks at the bearings so having 8 pounds left at idle isn't so out of line there.....Dan
 

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chevy states the minimum oil pressure is 15 psi. anything below 40 especially on a new engine is cause for consern. i build my engines to idle at 60 psi hot. the oil filter burst pressure is 300 psi. i have never had a bearing was out like some claim and melling tests all of thier oil pumps with a 1/4 hp motor so big pumps and high pressure dont draw to much power or kill bearings.the more oil you pump through your bearings the cooler they stay . the better oil film you have between your parts and thier bearing the longer it will last because it rides on the oil film not the bearings,when you have low oil pressures you have more jurnal to bearing contact and wear.
 
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