Losing Oil Pressure?
 

I'm haveing a problem losing oil pressure. while running at a mild speed 3500 rpms the oil pressure droped slowly to nothing. I replaced the oil pump and pick-up and bearings(mains and rods) over the winter. now after the engine ran great for 2-3 hours the same problem happened. Am I over looking something? motor is a 454 gen IV mostly stock, Imco Exhaust any advice is appreciated.

Re: Losing Oil Pressure?
 

what type of gauge electric or manuel if not manuel run a manuel and watch it.could also be all the oil on a high volume pump is pumping so fast your pump is cavitating add an extra quart.

Re: Losing Oil Pressure?
 

Need more details. Did you check it with a mech. gauge? Does it make any noise when it loses pressure? How do your temps look?

Re: Losing Oil Pressure?
 

Had a mechanical gauge on it for the first hour checking constantly, not a high volume oil pump , I replaced with a stock one. Water temp is 140-150 no oil temp gauge. First time lost pressure everything started squeeking and clanking around that's why I replaced the bearings.

Re: Losing Oil Pressure?
 

What is your oil pan capacity??? You also need oil temp gauge. What weight
oil are you running and do you run any type oil thermostat? What brand oil pump
did you put in?

Sorry for all the questions, but will help trying to figure out the problem.

Mike

Re: Losing Oil Pressure?
 

Oil capacity is 6 quarts, I know I need an oil temp gauge, i'm working on it. running 10-40 oil. stock replacement pump no-name brand. no oil thermostat.
thanks for the help I appreciate the replies.

Re: Losing Oil Pressure?
 

Do you have a remote mounted oil filter and oil cooler? If you do, is it possible that the oil bypass valve has too light a spring?

What happens is the restriction in the lines and fittings, remote mount filter and cooler add up to more pressure than the spring. The bypass valve opens because it "thinks" the filter is plugged. Hot oil then bypasses the remote lines and cooler, and goes straight back to the engine (without being filtered either). You have no oil temp gauge so you would not see the engine oil getting hotter and hotter.

Re: Losing Oil Pressure?
 

Thank you Tomcat, I do have a remote Filter and cooler I thought the bypass valve stuck open the first time this happened so I replaced the oil pump. how do I remedy this if it is the problem? but I am running the exact same set-up on the other motor and not having an issue.
and both my manual gauge and dash gauge read about 35-40 psi.

Re: Losing Oil Pressure?
 

The bypass Tom is referring to is in the oil filter adapter mounted to the block. It's a spring loaded valve that allows oil to pessurize the system if your filter, lines, or cooler is blocked. But this results in iol not being cooled or filtered.
Also, did you replace your cam bearings?

Re: Losing Oil Pressure?
 

Gary I did not replace the cam bearings. but the engine ran perfect for 2-3 hours before losing oil pressure. why would the bypass fail after so long?

Re: Losing Oil Pressure?
 

Cut the filter to see if anything came apart in the engine. Also, are both
engines oil level the same after sitting and after running???

Mike

Re: Losing Oil Pressure?
 

I will check the filter and yes both oil levels are the same. oil looks very clean I hope I didnt wipe out a new set of bearings again.

Re: Losing Oil Pressure?
 

35-40 lbs is that running or at idle, cold or warm? If that's what you get when you throttle up a fairly cool engine, that's low to begin with.

Re: Losing Oil Pressure?
 

I get around 30 psi at cold idle and 40 psi running back to 35 warmed up at idle. remeber a fairly stock motor . what should oil pressure be?

Re: Losing Oil Pressure?
 

With a $35.00 Melling hv pump I get 80 cold 1000 rpm, 50 warm idle, 60 at 4000 steady for an hour. I know some Mercruiser lo po engines only run about 45 but yours is worse. It would seem that your bearing clearances are wide enough to allow all of that oil to just flow through once it warms up.

Re: Losing Oil Pressure?
 

Maybe I should get the Melling pump this time around. Maybe the bypass valve is stuck open or there is something stuck in it? I need to check that this weekend.
Thanks for the replies.

Re: Losing Oil Pressure?
 

If you did not hot tank the block, buy a new cooler and thoroughly clean all other parts after the first bearing failure, you are now circulating metal from that failure. This metal quickly creates more metal from the new bearings. I assume since you did not replace cam bearings the block was not hot tanked. This is most likely the cause of the problem you have now. I hope it is not, but cutting the filter open now is your next step.

BT

Re: Losing Oil Pressure?
 

You are all wrong, dang it. DETONATION is your problem, will pound out main and rods in 45 min'. I bet you have a ton of metal in your oil filter.
Answer = Distributor curve is incorrect. junk dist, buy new and retool engine 1 more time. Good view of old bearrings would have told you detonation. You pounded the bearings to death then oil pressure goes to 5 psi.
Been there, done that. I had the exact results you are having, sorry dude.
Kurt

P/S you can not hear Detonation with water cooled exhaust. like a automobile cheap gas ping . must get total timming, not base. My junk distributor totaled out @ 1,200, way to low for marine severe duty appl', new distrib totaled @ 2,200 rpm. Big differance. :argue: :stupid:

Re: Losing Oil Pressure?
 

Well you must have way more information than the rest of us. Detonation typically causes a myriad of other problems first.

BT :cool:

Re: Losing Oil Pressure?
 

BT, you missed some lines on my Quote. Upon viewing of old bearings would have told you DETONATION, I may be Wrong since i can't see this Granade in person. My 2 cents B3


P/S I thought this would eark someone with a pro mind such as BT, not my intentions. :blaster:

Re: Losing Oil Pressure?
 

I think the first line "You are all wrong dang it!" fuzzed up my concentration on the rest or your quote. Of course detonation should be considered as a fundemental problem. I was curious what was going on before the first engine failed. No harm recieved BG :blaster: :blaster: :blaster:

BT :cool:

Re: Losing Oil Pressure?
 

Pretty hard to detonate a dead stock mark 4 454. Even with timing off, if it was. He doesnt give us much info on the first crash, maybe it ran out of oil or the pump failed. Ive run a couple of these with locked timing and never hurt anything.

Re: Losing Oil Pressure?
 

My timing was set perfect @ 28 degrees total advance at 3200 rpms. I dont think detonation was the problem, stock compression, 93 octane fuel and when I had the motor apart the first time the pistons were perfect. the other motor is also set exactly the same and is (so far) fine.

Re: Losing Oil Pressure?
 

All my timing is in at idle seeing I'm running locked at 32 degrees.
Hmmm?

Re: Losing Oil Pressure?
 

did you replace oil screen pickup when you replaced the pump or reuse the old one Just a thought

Re: Losing Oil Pressure?
 

I'm running locked timing also. Doubt if that is the problem. If it were me, I'd yank the engine and get out the mikes and the bore gage. Once, a long time ago, I did a quickie rebuild on a car engine. I used a berry hone on the cyl walls and just replaced the rings and bearings. It never ran well. It had low oil pressure and the rings never sealed well. Never again. Now I use a good machine shop and carefully inspect every piece that goes in.

Re: Losing Oil Pressure?
 

Looks like i'm tugging the motor this weekend to check the bearings and stuff then maybe to the machine shop. thanks again for all the input.

Re: Losing Oil Pressure?
 

Hello all again, stupoid P/C at work crashed yesterday, so now I am at home!.
There is a lot missing on discription of last failer. Was the oil boiled, did bearings show signs of heat = black and blue. if bearings big and small all looked like copper, no more babbott, with no heat stress = black and blew, then there was a timing issue. but once again I need to see before I should speak. good luck with tugging it, just find the problem by good inspection.
Also galley plugs can leak by cam in back, install oil restrictors if appl' alows it. Best of luck. B3 :)

Re: Losing Oil Pressure?
 

I had a stock 454 that I pounded out the bearings Big and small in 45 min'.
Damn Distributor based out at 9 degrees, did not check total because it was old Distributor from a small block Mercruiser. WELL, dand thing gave me 37 degree bump at 1,200 RPM. way to much to fast. End result was garbage lower end. Oh well, even My block specialist just looked at it and stated detonation. Oh yeah, I also had to much pitch on prop, lugged a BB and destroyed it. Oil temp wigged out also, but never reached boiling point before the detonation took lower out. Learn from ones own mistakes.
Plus I installed a stock mellings oil pump, others had to much volume =HV sometimes is not the answere either. My 2 cents. B3

Re: Losing Oil Pressure?
 

One other thing, I know you replaced bearings, but did you check the size of the main caps and big end of the rods? Any signs of a spun bearing? May need to resize rods & caps, grind crank 10 under too.
Gary

Re: Losing Oil Pressure?
 

I have not yet checked bearings this time around. I installed a newly turned crank .10 under and appropriate bearings last round. I didnt like the look of the last crank.
I still dont think my timming is the problem I'm looking toward the by-pass valve in the oil remote filter adapter I sure hope an 12 dollar part didnt cause me all this trouble.

Re: Losing Oil Pressure?
 

we had a similar problem on a guys car. It was a sbc with a remote mounted oil filter with braided steel aeroquip lines going to it. we had a mobil one oil filter on it and used straight 30 weight for break in on the motor. After running the motor for about 1 hour still using the 30 weight oil the oil pressure dropped to nothing. we changed the oil and filter several times and the same thing happened. What we eventually found was the braided steel lines going to the remote filter were swelling inside. Some kind of reaction between the inner rubber and the oil. we put new lines on it and the problem never came back. So maybe check your oil lines for swelling.

Re: Losing Oil Pressure?
 

Ditto whats Gary says. I had to cut all big ends and 10/10 crank, my new fricken crank!. resize main caps. :blaster: Was I stupid. B3

Re: Losing Oil Pressure?
 

I would have everthing checked just to be sure. I will probably get slammed for this but the old plastic gage on bearings just to double check clearances has always worked for me in a pinch. Make sure the crank is straight and journals are not out of round. Cam bearings on GenIV can cause low oil pressure. I still do not get why pressure would drop after run a while. Wish I new oil temp. Did you run after letting it sit a while and if so did oil pressure come back up for a while?

I have run with oil by-pass blocked for ever it seems. Just make sure you get some heat in your oil before you zing the throttle if you decide to block the by-pass.

I have seen moisture in the oil cause certain brand filters to clog causing LOW oil pressure but usually not zero after running for a short time.

Let us know what you find out. Good Luck. :drink:

Re: Losing Oil Pressure?
 

I bet you somehow got dirt in your bearings when you put them in. I saw this before on a Pontiac 400 Ram Air III. Oil pressure was good for 2 hours, then only good when cold after that. For oil pressure to be good with a hot motor, the bearing clearances have to be just right. Sounds like hot oil is finding it's way out through the bearings or distributor neck. I say it is not detonation, because that should break pistons and rings first.

Re: Losing Oil Pressure?
 

Here is my guess, when you installed the main caps one of them was installed out of the original sequence when they were re-installed thus creating wear and producing heat. Either way those bearings are now toast.

Good Luck.

Re: Losing Oil Pressure?
 

this is what I think it is. you probably have so much air in your oil the pump can't pick it up. there is also a relief spring in the oil pump itself. Perhaps it is hanging open? I don't see any bearing issues here unless you hot tanked the block with the cam bearings in and reusing them. Do you have any oil control or windage device mounted in the pan? you should.. perhaps the engine is tilted in a way that oil runs to the front?

Let me ask you this incase i missed it. Does the pressure ever return after a shut-down and cool-off?

Roby

Re: Losing Oil Pressure?
 

Actually I went to the boat this weekend, I removed the dist. and manually spun the shaft to the oil pump. With a manual guage hooked up i got 40 PSI so the oil pump is not clogged and did not fail. so then I start the engine to my suprise I now have oil pressure. 40 psi. but I heard a little knock sounded like a rod pin or sometheng so I pulled the motor did not tear it down yet but when I drained the oil it looked a little dirty for only haveing 2-3 hours on it. could I actually be boiling the oil and losing pressure? why would it take so long to boil and fail 1.5 hrs. running ?
I also replaced the oil cooler at the end of last season could this be the culprit?

Re: Losing Oil Pressure?
 

Answere is in the teardown, please reply with results. :drink: