Losing oil pressure as engine warms up!!

[belairrudy]

Hey guys... I am having a problem with my small block (327) in my "57". When I first start it up I have 60 PSI oil pressure. But as it warms up it begins to lose oil pressure. Once it is at running temperature (180-190) at an idle (700rpms) it is only getting around 5-10psi. If I step on the throttle the pressure will come up to about 35-40 but drop right back down once I let off the throttle. The engine only has about 700 miles on it since being rebuilt. I hoping it's not a spun bearing!!! What do you think?????::eek:

[ProjX57]

Just a couple question's:

What weight oil you using?
What was pressure after the rebuild to current mileage?
When did you notice it dropping?
Did you change the break in oil and filter?
Are you running a High Volume oil pump?

Ed :cool:

[belairrudy]

I am running 50w VR1 oil in it with a comp cam additive. Yes I did change the break in oil. The oil pressure was at 35 at an idle until this past weekend. I am running a high volumn standard pressure Melling oil pump.

[ProjX57]

I am sure you have done this, but have you checked to be sure that your gauge has not gone bad if it's mech or line collapsing when it gets hot, or a bad sender or gauge if elect?
There have been occasion's where high volume oil pumps have washed out the bearings. Hope this is not the case in your situation. Could be the oil pump screen has dropped down and is resticting flow to the pump also.


Ed :cool:

[gconnsr]

I am running 50w VR1 oil in it with a comp cam additive. Yes I did change the break in oil. The oil pressure was at 35 at an idle until this past weekend. I am running a high volumn standard pressure Melling oil pump.

If your running a high flow screen (chicken wire), which you most likely are, you probably have a small partical jamming your pressure check ball in the pump and not letting it close all the way. I've had this happen a couple of times with a high flow screen. Drop the pan and pull the pump, don't drive.

[belairrudy]

Already dropped the pan and checked the pump. Pump and screen are ok, defenitely have a pressure problem because I get valve train noise once I lose oil pressure.

[gconnsr]

Did you pull the check ball out of the pump to check?

[belairrudy]

To be honest... I actually replaced the pump. Because the pump that I originally put in it when I rebuilt it wasn't a high volume. So a local mechanic recommended installing a Melling high volume, standard pressure. So that's what i did. With a new screen!! Same problem!!!!!

[gconnsr]

To be honest... I actually replaced the pump. Because the pump that I originally put in it when I rebuilt it wasn't a high volume. So a local mechanic recommended installing a Melling high volume, standard pressure. So that's what i did. With a new screen!! Same problem!!!!!

Sounds like your screwed Dude, Sorry. I'd tear it down before you spin a bearing if you haven't already, sounds like your machinest blew it when he turned the crank or resized the rods, or you didn't clean out the crank journals good enough after it was cut.

[belairrudy]

You mean, I should have installed the high volume pump when I rebuilt it. RIGHT?????:(

[Ari]

Who built the motor? If not you, have you talked to the builder about the problem?

[belairrudy]

Actually I had my machinist short block it for me. So if that's the case it's on him. But how do I prove that????

[gconnsr]

Actually I had my machinist short block it for me. So if that's the case it's on him. But how do I prove that????

Well, I'm pretty sure it's on him. Take it to another shop and have them tear it down for diagnoses. He won't be able to argue with them, and I wouldn't let him touch the block again anyway. Get your cash back and have the other shop fix it.

[belairrudy]

Thanks. I was at the point of getting ready to purchase another short block. But now I take your advice, I appreciate your time.

[Chevy57Ray]

Well, I'm pretty sure it's on him. Take it to another shop and have them tear it down for diagnoses. He won't be able to agrue with them, and I wouldn't let him touch the block again anyway. Get your cash back and have the other shop fix it.

They other way around because getting the cash back will be a problem is to have him fix the engine at it cost with an extra warranty. You will have to trade ...

[belairrudy]

Well... one way or another at least I won't be taking all in the rear!!!!! You know what I mean.

[HYPURR DBL NKL]

When you had the pan pulled, did you see any metal in it? Also did you cut the filter and inspect it when you changed the pump? Third are you positive the pump screen to pan clearance is as it should be? Is the pump screen welded to the pump, maybe it has slipped? Have you always run the 50 wt oil, from day one since the rebuild? Is there any knocking coming from the engine? One last thing, there are three galley plugs behind the timing cover, if yours are the press in type, then maybe one has come loose and fallen out, this would lower your pressure for sure. I know this long, but I hope it's something simple for ya and not a PITA!

Phil

[210ratrod]

When you had the pan pulled, did you see any metal in it? Also did you cut the filter and inspect it when you changed the pump? Third are you positive the pump screen to pan clearance is as it should be? Is the pump screen welded to the pump, maybe it has slipped? Have you always run the 50 wt oil, from day one since the rebuild? Is there any knocking coming from the engine? One last thing, there are three galley plugs behind the timing cover, if yours are the press in type, then maybe one has come loose and fallen out, this would lower your pressure for sure. I know this long, but I hope it's something simple for ya and not a PITA!

Phil

If you experienced this problem suddenly, I'd be willing to bet one of those galley plugs behind the cam gear popped out like Phil suggests. They don't fit in very tight, or at least the ones I put in didn't. When I put my 283 together, I was paranoid of this happening to me out on the road, so I staked them all in place with a center punch four times each. Like Garry said, don't drive it 'till you find out whats wrong for sure.

Tim

[belairrudy]

When I first rebuilt the engine I was running 20w-50w VR1. My oil pick up screen is a bolt on screen. If one of the plugs came out behind the timing chain gear, wouldn't I have low oil pressure at all times not just after it warms up? The only abnormal noise I am getting is in the valve train. Nothing down below.

[belairrudy]

YES unfortunately there was signs of metal in the pan. Therefore I think I am up you know what creek!!!! I also forgot to mention to you guys. I was not informed that I needed to install a cam additive to my oil when I first started my engine on it's initial sart up and cam break in period!!! Therefore.. my cam went flat. So I had to install a new cam. Do you think that maybe some of the cam particles could be causing blockage. Heck.. I don't know, I am lost and just fishing for ideas guys. before I go and spend a lot of money.

[auggie56]

Who told you to use a fifty weight motor oil ? That is just way to thick, to give adequate lubrication, particularly when the engine is cold. Even if it's multi vis.

[gconnsr]

YES unfortunately there was signs of metal in the pan. Therefore I think I am up you know what creek!!!! I also forgot to mention to you guys. I was not informed that I needed to install a cam additive to my oil when I first started my engine on it's initial sart up and cam break in period!!! Therefore.. my cam went flat. So I had to install a new cam. Do you think that maybe some of the cam particles could be causing blockage. Heck.. I don't know, I am lost and just fishing for ideas guys. before I go and spend a lot of money.

After hearing all this I think you should take it back to the original rebuilder Rudy. It sounds like you really weren't up on your skills like you needed to be. Most likely the rebuilder will work with you, show you where you went wrong, and cut you a nice break on the fix. It's still going to be cheaper than buying another engine. You gave it your best shot, take it back and learn where you went wrong so it doesn't happen again. I call this paying for your education, it happens dude.

[chevender]

YES unfortunately there was signs of metal in the pan. Therefore I think I am up you know what creek!!!! I also forgot to mention to you guys. I was not informed that I needed to install a cam additive to my oil when I first started my engine on it's initial sart up and cam break in period!!! Therefore.. my cam went flat.

I think you just answered your own question. If the cam went flat it sent all kinds of chimps and scrutles all through your engine. Obviously they are blocking and or restricting oil flow. Time to remove the engine and tear it down for a clean out and a check. If your lucky you can get away with just a clean out. I would let a shop check it for you.
Rick

[Old Buzzard]

"Therefore.. my cam went flat. So I had to install a new cam. Do you think that maybe some of the cam particles could be causing blockage. Heck.. I don't know, I am lost and just fishing for ideas guys. before I go and spend a lot of money."

A flattened cam will put enuf trash in the engine, to take out the brgs...
I deal w/ this frequently w/ turbo Buicks... It's a mandatory teardown, clean out of ALL passages, reassemble/replace the brgs... including the cam brgs...

A couple other "items":
Ditch the hi vol pump.
Ditch the 50 wt oil. This is not a T/F application.:D
10/30 is plenty good for the street.

[ProjX57]

If you had metal in the pan from the cam going flat, then it could have spun a cam bearing, that would cause the oil pressure to drop too, but the oil pump has picked some of the metal up probably, and if you keep running that motor I am afraid you are going to hear some real bad noises when it spins a rod or main bearing, and that is going to be even more $$$$$$$ to fix. If it takes out a main or rod bearing, Main= align boring block, Rod=new rod or rods, and could mean a new crank also. In any case you are playing with fire after everything that has happened..................Better to be safe than sorry at this point. My .02

Ed :cool:

[benniemo]

Hey Rudy, I am running a chevy smallblock 305 in my 55 chevy and my oil pressure would also drop off when the engine got up to operating temp. motor runs like a top. my buddy who owns an engine shop put a new oil pump in and I have more oil pressure when I throttle up.but it still drops off at idle. I heard from a lot of guys on here some saying this is a common problem with small blocks. As long as I have 60 pounds at throttle and car runs good I decided not to worry about idle pressure. If you can figure out what is causing your problem be sure and post it

good luck

bennie

[571504d]

My 2 cents.....the flat camshaft most definately put trash in the oil, but we're talking very small particles that should have been caught by the oil filter and not large engough to block or plug anything. This being said, junk in the oil increases wear. This was a rebuild, but sometimes it's common to rebuild and not change the cam bearings, were they new? It only takes 10 psi of oil pressure per 1000 rpm to adequately lube an engine, and oil pressure drop at idle is normal, but large pressure drops at idle usually indicate sloppy cam bearings. Spun bearings generally increase oil pressure due to the blockage of an oil passage as the bearing slips in the cap. Sounds like to me if you are getting around 10 psi at 700 rpm idle, you're not out of oil. When the cam went flat, did the bearings get changed? Are you sure the noise in the top end is not a lifter needing adjustment since the cam change? Most of the time just one lifter being set different from the others sounds worse than all of the lifters being sloppy. If it were me, I'd try to avoid the knee jerk reactions and start with some simple investigation. You've aready pulled the pan and changed the pump. Don't worry about the drop in pressure, as long as it stays in that 10 per 1000 ratio. Check the lifter adjustments, and see if it sounds better, then maybe I'd see about a cam bearing swap, to get the idle pressure up.

[gconnsr]

My 2 cents.....the flat camshaft most definately put trash in the oil, but we're talking very small particles that should have been caught by the oil filter and not large engough to block or plug anything. This being said, junk in the oil increases wear. This was a rebuild, but sometimes it's common to rebuild and not change the cam bearings, were they new? It only takes 10 psi of oil pressure per 1000 rpm to adequately lube an engine, and oil pressure drop at idle is normal, but large pressure drops at idle usually indicate sloppy cam bearings. Spun bearings generally increase oil pressure due to the blockage of an oil passage as the bearing slips in the cap. Sounds like to me if you are getting around 10 psi at 700 rpm idle, you're not out of oil. When the cam went flat, did the bearings get changed? Are you sure the noise in the top end is not a lifter needing adjustment since the cam change? Most of the time just one lifter being set different from the others sounds worse than all of the lifters being sloppy. If it were me, I'd try to avoid the knee jerk reactions and start with some simple investigation. You've aready pulled the pan and changed the pump. Don't worry about the drop in pressure, as long as it stays in that 10 per 1000 ratio. Check the lifter adjustments, and see if it sounds better, then maybe I'd see about a cam bearing swap, to get the idle pressure up.

That engine is done dude, It had metal shavings in the oil. It has to be torn down, everytime he starts it he is causing more damage.

[gconnsr]

Hey Rudy, I am running a chevy smallblock 305 in my 55 chevy and my oil pressure would also drop off when the engine got up to operating temp. motor runs like a top. my buddy who owns an engine shop put a new oil pump in and I have more oil pressure when I throttle up.but it still drops off at idle. I heard from a lot of guys on here some saying this is a common problem with small blocks. As long as I have 60 pounds at throttle and car runs good I decided not to worry about idle pressure. If you can figure out what is causing your problem be sure and post it

good luck

bennie

Changing the pump was a good idea because I have seen oil pump pressure valves get stuck, but sometimes a machinist will put the bearing tolerance on the lose side if he thinks your going to be racing, if thats the case there's nothing you can do about it and it's not really hurting anything. Just to clarify, this is for Bennie, Rudys engine is all done and the most likely cause was over-adjusting the valves on the first cam. When he installed the second cam he also installed a high volume pump with a high flow screen, this allowed any small shavings that where still in the engine to go through the pump. No matter how you look at it, he's all done. If he keeps running it, it's most likely going to scatter.

[chevender]

Chevy V8's breath and oil better than any engine should be allowed to. Having said that, a high volume oil pump is not needed. It has already been proven that some pumps will empty the pan at high RPM's. That's why somebody developed reduction lifters to keep the oil in the pan. A good stock pump is more than adequate for the street.
Rick

[belairrudy]

Well...looks like I am going to be pulling the engine and taking it to my machinist. Chalk it up as experience I guess. Hey....I learning the hard way. My dad is more experienced than I am. But his lung disease keeps him from physically doing the work. He can only observe me and coach me through adjustments and engine building. Thanks for all your help guys. Next time I will ask questions before instead of after. That way it won't hurt the pocket book so much!!!!!

Rudy

[zonker]

Hey Rudy, I am running a chevy smallblock 305 in my 55 chevy and my oil pressure would also drop off when the engine got up to operating temp. motor runs like a top. my buddy who owns an engine shop put a new oil pump in and I have more oil pressure when I throttle up.but it still drops off at idle. I heard from a lot of guys on here some saying this is a common problem with small blocks. As long as I have 60 pounds at throttle and car runs good I decided not to worry about idle pressure. If you can figure out what is causing your problem be sure and post it

good luck

bennie

DITTO for me and why are you using 50wt. oil

[gconnsr]

Well...looks like I am going to be pulling the engine and taking it to my machinist. Chalk it up as experience I guess. Hey....I learning the hard way. My dad is more experienced than I am. But his lung disease keeps him from physically doing the work. He can only observe me and coach me through adjustments and engine building. Thanks for all your help guys. Next time I will ask questions before instead of after. That way it won't hurt the pocket book so much!!!!!

Rudy

I'd rather learn the hard way than pay everyone to do everything for me Rudy, at least your learning:tu

[Chevy57Ray]

Rudy, if your machinist do not know engine, you must considerate going to a PRO because since there is a lot of tricky pieces in an engine and it could make you learn the hard way again. M2C

[571504d]

That engine is done dude, It had metal shavings in the oil. It has to be torn down, everytime he starts it he is causing more damage.

Not to argue, but The speed shop gave me the wrong camshaft by mistake when I was building my engine. I too have a high volume oil pump. When I started my engine the first time it started without any problems, but wouldn't time right, nor would the valves stay adjusted. Long story short, It got where It wouldn't run at all and I tore it back down to the cam and found much of the lifters in the pan as .....metal shavings.... got the right camshaft, new lifters, cleaned it up, put it back together runs great, great oil pressure. But go ahead and assume the worst if you want. Doesn't sound that big of a deal to change cam bearings and clean it up to me.

[eaton615]

just a thought, try plastigauging the rods and mains before a complete tear out and down. if theycheck okay you might want to check the cam bearings. this ia another area where your machinist could have dropped the ball. unfortunately, if this is the problem, it will require complete tear down. you didnt mention the cam area or what cam you used, i have seen many aftermarket cams and bearing fail due to varied reasons, incorrect installation, incorrect break in oils/assembly lubes, poor machine work etc.

[belairrudy]

That is going to be my first step. My Dad also recommended checking the main bearings before I pull the engine. So that's what I am going to do. But.... since I foung metal in the oil, I still think I am going to be pulling the engine anyway. I installed a Crane Blue Racer Cam in it the secong time around and used a comp cam additive. I even used the additive when I changed the break in oil.

[HYPURR DBL NKL]

X's 2 on the Rotella T oil. I would also add some cam break in additive as well, just to be safe. If you don't have a lot of experience, then I would pull the engine and have some one else you trust go through it, to make sure it's done right, so you're not doing this again in the near future. I wish you the best of luck with this!!

Phil

[belairrudy]

Hey guys... I am having a problem with my small block (327) in my "57". When I first start it up I have 60 PSI oil pressure. But as it warms up it begins to lose oil pressure. Once it is at running temperature (180-190) at an idle (700rpms) it is only getting around 5-10psi. If I step on the throttle the pressure will come up to about 35-40 but drop right back down once I let off the throttle. The engine only has about 700 miles on it since being rebuilt. I hoping it's not a spun bearing!!! What do you think?????::eek:
Update on this thread: I have installed a rebuilt 350 short block and no longer am having any oil pressure problems. Haven't disassembled the 327 block yet to see what caused the oil pressure drop though. Will do that some time in the winter. To busy CRUISING during the nice weather months. Thanks for all your help! :beer:

Rudy

[ProjX57]

Glad your back on the road, and cruising Rudy...................... :beer:
Let us know when you find the problem with the 327 for future reference if you would.......................

[Typhoontx]

The symptoms sounds like a problem I once had, I found 1 of the oil galley plugs behind the cam sprocket had popped out. If thats what happend you might find the plug lying in the oil pan. If so its a easy fix

regards, robert

[571504d]

A Spun bearing usually increases oil pressure because it blocks the oil passage for that bearing causing the overall pressure to build.

[CNC BLOCKS]

We just went through this sagga with a customer with a 327 that had low oil pressure and the oil was getting dirty with in 100 miles. We found a lot of problems as all galley plugs were left out behind the timing gear and the only thing that may have saved him was the other engine shop put a high volume pump on the engine, We did find that the main line needed a ling hone and a leak down test showed leak downs from 10% to 35% and it only had 400 miles on this build.

Even though the low oil pressure the rods bearings look fine and the mains showed some dirt and uneven wear. I am a big advacate of line honing as no block leaves my shop with out this done.

Pic of line honing.
http://i7.photobucket.com/albums/y276/CNCBLOCKS/LINEHONE004.jpg

Here is a pic of the main bearings.
http://i7.photobucket.com/albums/y276/CNCBLOCKS/BADMAINLINE.jpg

One other area was the pressed in plug under the left head was not pulled out as there is no way to clean that oil galley out when its cleaned.

Here is a pic taping the oil galley out for a 1/4 pipe plug.
http://i7.photobucket.com/albums/y276/CNCBLOCKS/truckandplug011.jpg

Since the engines is back together the oil is staying clean and again we are also a big advicate of torque plate hone.

Here is a pic of plate honing.http://i7.photobucket.com/albums/y276/CNCBLOCKS/LITTLE-MBLOCKANDLIFTERBOREFIXTURE013.jpg

Here are 2 links about this problem
http://forums.corvetteforum.com/c1-and-c2-corvettes/2289212-oil-pressure-problem-saga.html

http://forums.corvetteforum.com/c1-and-c2-corvettes/2374823-engine-rebuild-oil-pressure-saga-update.html

[AceHole56]

I hate to shed negative light on the matter, but this is EXACTLY the same problem I had with my 327 last fall. It would start up with great oil pressure, but by the time it warmed up, I had 5 pounds at idle. (Some will say that's fine because Chevys only need 7 pounds per 1000 rpms, which is true, but I prefer more) After I did everything I could (New standard pump, new HV pump, straight 30w, 40w, VR1 50w), the same thing kept happening. I thought that maybe I had knocked a cam bearing out of whack, but when I decided to pull it and tear it down, the truth revealed itself: Every single bearing was scorred down past the brass. The crank was grooved everywhere, and to make matters worse, my beloved crank had already been previously undercut .020 under. I hope to rebuild mine this winter.

I hope that it's something simple like a faulty guage or something, but I would almost bet that it's a bearing issue. :confused0006:

[CNC BLOCKS]

I hate to shed negative light on the matter, but this is EXACTLY the same problem I had with my 327 last fall. It would start up with great oil pressure, but by the time it warmed up, I had 5 pounds at idle. (Some will say that's fine because Chevys only need 7 pounds per 1000 rpms, which is true, but I prefer more) After I did everything I could (New standard pump, new HV pump, straight 30w, 40w, VR1 50w), the same thing kept happening. I thought that maybe I had knocked a cam bearing out of whack, but when I decided to pull it and tear it down, the truth revealed itself: Every single bearing was scorred down past the brass. The crank was grooved everywhere, and to make matters worse, my beloved crank had already been previously undercut .020 under. I hope to rebuild mine this winter.

I hope that it's something simple like a faulty guage or something, but I would almost bet that it's a bearing issue. :confused0006:

If that press in plug is still in your block and has never been removed that maybe where the problem started and more so if the block has been baked and blasted.

We also plug the oil filter bypass so all the oil is filtered before getting to the bearings, Also look under the rear main cap ans see if the 1/2 plugg is there if left out once the oil filter is full of oil the oil will bypass the filter as it will go the path of least resistance. (Most people think it hurts oil pressure but it don't until the bearings are wiped out from debris)

The engine we built in my post we used a Melling select pump standard volume high pressure which is the old Z-28 replacement pump, This engine runs 45 pounds at idle and 65 cruising.

Now I have seen guys not put the rear cam bearing not in all the way and leave the groove in the housing bore exposed.