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0 oil psi at idle at temp

6K views 46 replies 23 participants last post by  northern56 
#1 · (Edited)
Hello everyone
I hope this is in the right place I have a 350 bored .040 solid lift lunati cam shaft 1.6 roller rockers. The engine shows 60 psi at idle when cold but like normal pressure drops as engine warms up but at 190 degree it has 0 oil pressure on mechanical gauge which I have changed twice. I'm running straight 30 weight oil for break in I have put 7 miles on the engine I put threaded galley plugs in front and replaced ones in the rear. Added extra 2 qts oil to make sure pickup had not came out of standard melling pump.i also plastigauged the crank bearings and all was around. 002 I'm at a loss here and digging for Info thanks in advance



I have torn the engine back down 7 to 10 miles on engine and all rod and main bearing are wiped out after removing the crank I have found all the oil holes in the cam bearings to be straight in line with the main journal oil holes the front cam bearing has 2 oil holes and 1 of those is lined up with main journal could this have caused the problem
 
#7 ·
Yes I checked rods and mains and had new cam bearings installed I'm leaning towards the cam bearings myself. I was told you could actually spin a cam bearing but I've had no luck with info on bearing orientation to know if they are correct
What was done during the engine build? Is everything new from cam bearings to main and rod bearings?
Adding extra oil can be dangerous if you go 2 extra quarts, as it will result in the crankshaft weights slapping the oil, and cause huge issues! I hope you didn't run the engine long with 2 qts. extra?
Straight 30wt. should be fine, and even lighter if the engine is well built wont cause low oil pressure. I run VR-1 10-30w in mine and no problems.
Everything is new rod bearing and main bearing mic standard per machine shop cam bearings new only reused the block Everything else came from summit racing after changing to mechanical gauge and then another mechanical gauge to be sure that it wasn't a gauge issue I thought pick up may have came out of pump because I didn't tack it to pump added 2 qts more oil still no pressure at idle but at 1500 to 2000 rpm I have 50 lb when hot was told I could have spun a cam bearing but I cannot find good info on checking cam bearing orientation
 
#3 ·
A very common issue is moly additive plugging oil filter on fresh builds. nasty stuff. (start with new oil filter).. cut old one looking for excessive metal

Q: What about oil pump pickup tube. Welded or bolted bon...if so did they remove cover before... arcing and sparking. Just had one very similar in a bbc.. arced to gears..ground up pump.
 
#9 ·
A very common issue is moly additive plugging oil filter on fresh builds. nasty stuff. (start with new oil filter).. cut old one looking for excessive metal

Q: What about oil pump pickup tube. Welded or bolted bon...if so did they remove cover before... arcing and sparking. Just had one very similar in a bbc.. arced to gears..ground up pump.
I did the build myself except cam bearings and machine work and putting piston on rods I just pressed pickup in pump no weld that's why I tried adding extra oil I was told maybe a spun cam bearing but no good info on checking them
 
#6 ·
Hello everyone
I hope this is in the right place I have a 350 bored .040 solid lift lunati cam shaft 1.6 roller rockers. The engine shows 60 psi at idle when cold but like normal pressure drops as engine warms up but at 190 degree it has 0 oil pressure on mechanical gauge which I have changed twice. I'm running straight 30 weight oil for break in I have put 7 miles on the engine I put threaded galley plugs in front and replaced ones in the rear. Added extra 2 qts oil to make sure pickup had not came out of standard melling pump.i also plastigauged the crank bearings and all was around. 002 I'm at a loss here and digging for Info thanks in advance
What was done during the engine build? Is everything new from cam bearings to main and rod bearings?
Adding extra oil can be dangerous if you go 2 extra quarts, as it will result in the crankshaft weights slapping the oil, and cause huge issues! I hope you didn't run the engine long with 2 qts. extra?
Straight 30wt. should be fine, and even lighter if the engine is well built wont cause low oil pressure. I run VR-1 10-30w in mine and no problems.
 
#36 ·
What was done during the engine build? Is everything new from cam bearings to main and rod bearings?
Adding extra oil can be dangerous if you go 2 extra quarts, as it will result in the crankshaft weights slapping the oil, and cause huge issues! I hope you didn't run the engine long with 2 qts. extra?
Straight 30wt. should be fine, and even lighter if the engine is well built wont cause low oil pressure. I run VR-1 10-30w in mine and no problems.
I have torn the engine back down 7 to 10 miles on engine and all rod and main bearing are wiped out after removing the crank I have found all the oil holes in the cam bearings to be straight in line with the main journal oil holes the front cam bearing has 2 oil holes and 1 of those is lined up with main journal could this have caused the problem
I only know about 10% of the knowledge most others on this site have.
I did Goggle "sbc cam bearing orientation on oil pressure" and it came up with lots of hits.
I only looked at the first one and didn't read all of it as it is fairly long.
It did seem to be interesting and you might also try your own Google search too.
Thank you for the Info I'm positive I've found the problem in the cam bearings I've looked at 2 other sbc and cam bearings are not lined up like mine guess it's time to find a new machine shop and get my block checked it just a hard lesson bought
 
#8 ·
Are you sure your oil gage is reading direct oil pressure? I mean is the gage plugged into an oil line? If you are depending on an electronic sensor that could be your problem. For the past several years cars have come with dummy gages that operate like dummy lights. That is that if the pressure drops below a set value, say 15 psig, the red light is supposed to come on. On these dummy gages, if the pressure drops below the set point the gage needle drops to zero. You may actually have 14 psig but the gage will read zero because it is not enough to trip the switch. Once you exceed 15 psig the dummy gage will show 50 psig all of the time regardless of the actual pressure. A gage that is operated by actual oil pressure (no sensor involved) would show the 14 psig. So, if you have a pure mechanical gage that reads zero at idle you do have a problem.
 
#11 ·
No sir no sensor it was running what I call an electric gauge but I did away with that first and put a mechanical auto meter oil psi gauge in then checked that with a mechanical Stewart oil pressure gauge I have issues with engine just not sure if bypass is the issue or cam bearings which was installed new by machine shop. Literally no oil to either head at 190 degrees coolant temp
 
#10 ·
Dump the oil spin on a new wix filter and put 5 qt of 15/40 and there and start it up. Run it up to temperature and if it still drops dump the oil and cut the filter open.

Do you have a bore snake?
If so fish it up through the oil drain plug and look to see that the pickup is still on the pump.
 
#12 ·
Dump the oil spin on a new wix filter and put 5 qt of 15/40 and there and start it up. Run it up to temperature and if it still drops dump the oil and cut the filter open.

Do you have a bore snake?
If so fish it up through the oil drain plug and look to see that the pickup is still on the pump.
I do have a bore camera have not thought about running it through drain in pan thank you I will check pickup then try 15w40 wix is my go to filter was burnt buy Fram years ago
 
#13 · (Edited)
Wow, lets slow down for a second.

You said cold oil pressure shows 30 PSI at idle, but what is that idle RPM?

You said zero oil pressure at 190 degrees, then you said no oil to either head. what happens if you raise the idle by 1000 RPM ?

Where on the block are you tapping in for oil pressure?

Worn cam bearings should not reduce pressure by this amount.



Read my posts and answer those 3 questions.

Edited after reading you are running a solid lifter program
 
#32 ·
I have torn the engine back down 7 to 10 miles on engine and all rod and main bearing are wiped out after removing the crank I have found all the oil holes in the cam bearings to be straight in line with the main journal oil holes the front cam bearing has 2 oil holes and 1 of those is lined up with main journal could this have caused the problem
 
#15 ·
Al, I definitely would NOT be running engine without oil pressure. Any more time running engine without oil could/will result is significant consequences to all your hard work. Because engine temp AND oil pressure are important indicators during engine break-in, I installed a separate set of those gauges as well as a separate tach in engine compartment so I could monitor these parameters throughout initial start up.

What is puzzling is you're getting an oil pressure reading initially and up until 190 degrees of engine temperature. After engine is warm, zip! I find it hard that a machine shop would screw up installation of new cam bearings.

Although not what any of us want to do, dropping the oil pan may be necessary; even worse, removing motor and looking further for the culprit. Before getting to those drastic steps, be VERY methodical in addressing what others have suggested. Good luck and keep us in the loop!
 
#16 ·
As mentioned earlier, verify oil pump regulator is free, moving. Remove roll pin, inspect. Wouldn't hurt to look at oil pump inside cover surface, gears for deep scoring. 0psi... is troubling... Main bearings are oil key to pressure.. be sure correct size. We had recently found wrong under size on box, diff from bearing. Quality Clevite brand. Agree wuth spun cam bearing...but not 0psi. Good Luck.
 
#17 ·
You would never have low oil pressure with a cam bearing out of alignment with the oil passage ports. Since the cam bearings only usually have one hole it needs to be aligned correctly. If the hole was blocked for any reason the pressure would be higher, and it would quickly have a cam failure from oil being restricted.
Since your problem is the opposite, there's an issue of something not restricting oil flow properly, and not allowing pressure to build to safe operating levels.
If it was my engine I'd be dropping the pan and replacing the oil pump for starters. I'd go to a good quality Melling oil pump to see if it's better. A lot of work, but it could save an expensive engine rebuild again.
 
#18 ·
The way that cam bearings can affect idle oil pressure is if they are gouged up from a sloppy installation of the cam into the block at assembly.

Question - even though it's idling at "zero" oil pressure, does pressure increase when you open the throttle? To what pressure?

Very unusual to have 0 pressure, but 5 or 10 psi at hot idle is fairly common.
 
#19 ·
There is a method to check for internal leaks Years ago I had a Chevy factory rep who was pretty smart.In that time frame early 70s we had a lot of complains of engine knock. We found it to be a front main bearing knock. He had us use a old freon 30lb can he had fitted it so it could be filled with oil with a line to be connected into the block at the oil pressure port for the gauge.Air pressure was applied to the tank & with the pan off the engine he would have us count the number of oil drips from the front main bearing in 30 or 60 seconds can't remember the details now .We would then change the front main bearing to a .001 .002 or a mixed combination of these to reduce clearance which then reduced the oil flow. This worked correcting main knock later GM came out with a concentric bearing in std. 1 or 2 thousands sizes that was a better fix & the problem eventually went away. The reason I mentioned this long winded rant is that you might be able to use a pre oiler pull the pan & see where you have a loss of pressure.You might even have everything set up remove most the oil pan bolts run the engine long enough to start to see a loss of oil pressure pull the pan & see if you can determine where the pressure loss is with the oil system pressurized.I also had the same situation you have I rebuilt a 300hp 327 for myself took a quick look at the bearings as I was pulling it apart the bearings were all the original GM factory bearings the rods were standard replaced both rods & mains with standard bearings put it together great oil pressure cold 0 -5psi when hot once I checked I found the mains were .009 under size from GM yes they often used under sized bearings. I was around 19 at the time but something I never forgot. Again sorry for the long rant
 
#28 ·
Thank you for the info I have pulled the engine back down and of course the rods and mains are wiped out mains 1 and 2 are gone 4 and 5 are gone 3 still looks new all the rods are wiped out almost looks like the block should have been line bored I looked at the cam bearings the oil holes in the bearings is directly in line with the main journal oil holes and the information I have found says they should not be lined up in this manner is there any way I can know for sure this is the problem
Sorry for the long reply but I've never had this issue with sbc or bbc
 
#26 ·
I have seen this once in my engine building career! The rear cam bearing was not installed all the way into the bearing bore leaving the oil holes exposed to the rear of the camshaft. The oil pressure was draining out of the holes bored in the rear camshaft journal..
This engine produced the same oil pressure problem that you speak of..
 
#29 ·
I have torn the engine back down 7 to 10 miles on engine and all rod and main bearing are wiped out after removing the crank I have found all the oil holes in the cam bearings to be straight in line with the main journal oil holes the front cam bearing has 2 oil holes and 1 of those is lined up with main journal could this have caused the problem
 
#27 ·
I have seen this once in my engine building career! The rear cam bearing was not installed all the way into the bearing bore leaving the oil holes exposed to the rear of the camshaft. The oil pressure was draining out of the holes bored in the rear camshaft journal..
This engine produced the same oil pressure problem that you speak of ..
 
#30 ·
I have torn the engine back down 7 to 10 miles on engine and all rod and main bearing are wiped out after removing the crank I have found all the oil holes in the cam bearings to be straight in line with the main journal oil holes the front cam bearing has 2 oil holes and 1 of those is lined up with main journal could this have caused the problem
 
#35 ·
I only know about 10% of the knowledge most others on this site have.
I did Goggle "sbc cam bearing orientation on oil pressure" and it came up with lots of hits.
I only looked at the first one and didn't read all of it as it is fairly long.
It did seem to be interesting and you might also try your own Google search too.
 
#40 ·
If you had read through the article it does state that the early style SBC might only have the oil holes pointed straight down.

"As a case in point, earlier small-block Chevy blocks might feature only an oil-feed hole that aligns with the main cap oil passage, in which case the cam bearing's oil hole must align with the saddle's oil hole. By comparison, the '92-97 Chevy LT1/LT4 features a full-circle oil groove, which might lead you to think that exact clock position of the cam bearing oil hole is not important (since oil will feed into the space between the bearing and cam journal and will travel along this groove, eventually feeding into the bearing's hole anyway). However, even if a full-circumferential groove is present, as we mentioned earlier, it is necessary to position the cam bearing's oil hole at a specific position (at approximately the 2:00 position as viewed from the block front) in order to allow cam rotation to create a slight oil "wedge" during operation. This more efficiently creates an oil film between the cam journal and its corresponding bearing. Also, if the oil holes in a full-groove-type setup are aligned exactly (oil hole in the bore saddle and oil hole in the cam bearing), oil pressure can potentially feed-back, momentarily preventing oil from traveling around the journal, which can minimize the necessary oil wedge."

So it may be OK pointing straight down depending on the year of the engine block.
 
#41 ·
If a short bolt that is a head bolt was used to bolt the oil pump on the bolt will bottom in the main cap = loose pump.
Check the hole in the block by the main cap to insure there is a plug in the hole.
Engine upright the cam bearings get installed with the oil hole @ 2 o'clock the front bearing with 2 holes = 10 & 2 o'clock. The bearings have part numbers on them consult the box they came in for correct installation location. The 2 hole cam bearing is the front bearing extra weep oil is required in that location to lube the top timing gear thrust surface against the block, flat tappet cam lobes are ground high on the rear edge to spin the lifters & force the cam to the rear of the block.
Use a priming tool to check pressure & make sure that all rocker arms are getting oil.
Luck.
 
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