360 losing oil pressure when reved up.

If it smokes on start up the valves seals are bad. They're so bad they've hardened, broken apart, fallen into your oil pan and are plugging the pick-up tube screen.

I finally pulled the oil pan off and removed the oil pickup tube. it was not clogged.
the motor is on an engine stand now.
the motor has never been apart and only has a little over 70,000 miles on it but it is a 1972 so its old.
how can I tell if the bearings are the issue?
I would like to pull the heads and have them redone and continue to use the motor in my pickup. I was hoping to get by with just installing new rings and bearings since it is low mileage and still ran good.

Wow, an OP reviving a 5 year old thread

Carefully remove the main caps, take lots of pictures and post them up here. Don't mix anything up or drop it yet.

I'm assuming you don't have access to a bore mic and calipers to measure your clearances. You could use some plasti-gauge and see what the clearances are, although this isn't very accurate. You could measure, get new main bearings, re-measure, and they should at least be tighter.

I'd put a new oil pump in it too.

I would 2nd the worn main bearing theory, I've been there too

wow it has been 5 years I pulled the motor out back when I had the oil pressure problem and dropped in a temporary motor, now the temporary motor is needing replaced. since it was worn out when I got it. but this 360 is a good motor and I didn't want to screw it up. I have owned it since it only had 30,000 miles on it. now I need to fix it and get it back in my truck.
I don't have a bore mic, I do have a cheap set of digital calipers.
I will pull the caps off and get pictures, I will mark the caps to make sure I get them back on the right place. probably tomorrow.
thanks

Old Quaker Sludge oil used to cause lots of that years ago. Gotta love the old paraffin based oils.

took some pictures of the main bearings. there was some small groves In the bearings but didn't seem to be any on the crank.

number one

number two

number three

number four

number five

here is one of the crank at the front bearing.

does this look like something that could cause an oil pressure drop?

not to me.EDIT Meaning the crank looks OK but I backed up the posts & the bearings need replaced. You didn't happen to note the psi's at idle/when revved/at speed before you tore it down did you? & confirmed with a good gauge. I'm missing something

I had a mechanical autometer gauge that was almost new. and I think it had around 40 psi when driving. and as soon as I punched on the gas and the rpm's went up it would start loosing oil pressure. I don't remember what it was at idle but remember that it seemed to be normal or similar to my other cars, my dart.
a few months before this started happening the motor sat un started for about 4 years, then I pulled the old 2 barrel carb off and put a 750 holley on it, because that is what I had . and pulled out the automatic trans and put in a 4 speed. it never got run hard the whole time I had the auto trans in it and even after I put the 4 speed in I don't think it ever saw over 5000 RPM.

I'd change the rod/main bearings, go with a new sealed power std vol/psi pump, make sure the pickup ain't too far off of the pan bottom, use a non Fram filter. since you are torn down I'd rering with some plasma moly file fit rings & dingleberry hone the cyls lightly with their 320 grit flexhone. That far down you could almost bore for new pistons to get the SCR up but a person has to draw the line somewhere. You said the pickup is clean & the NPT plug at the rear of the DR horizontle gallery INSIDE the valley is in place. EDIT to ans the orig Q I'd guess a combo of worn bearings and or partly clogged filter/worn pump assuming the gallery plug is in/pickup distance correct/pickup not partly plugged

Looking at your description, the answer isn't the main bearings or the pump.

Here's why:
If the engine will develop 40psi at normal speed, the pump and bearings are okay. Now, it wouldn't hurt to replace the mains, but again, if the clearances are tight enough to maintain 40psi at say, 2500 rpm, there is nothing that will cause them to loosen up as you go higher. And if the pump will pump enough oil to develop 40psi back pressure (which is what your gauge reads) it won't pump less at higher rpm, assumoing it has oil to pump.

You can check your bearing clearances with Plastigage and get a ballpark number. I bet it's less than many on this board normally run.

So the question is, why won't the pump PUMP ENOUGH OIL at higher rpm? Two reasons stick out in my mind:

1. There's not enough oil to pump. This could be because, a. Sludge in the engine is slowing drainback to the sump, b. The pan is inadequately baffled and on acceleration the oil runs away from the intake, c. There isn't enough oil in the crankcase, d. The oil is foaming, e. The oil pickup tube has some sort of internal blockage that is causing the pump to cavitate.

2. The pressure relief valve on the pump gets stuck open and most of the pumped oil goes back into the sump. This would usually display other symptoms as well, and is a little more far-fetched.

Don't buy anything except Plastigage until you have this figured out.

One of the key pieces of information is that the engine was a two-barrel grocery-getter engine and it sat for periods of time, then you put a different carb on it and somewhat drove it. That means to me that you don't know how it was driven or maintained before you got it. Low mileage doesn't mean lack of sludge.

R.

although it has nothing to do with oil pressure, replace the plastic toothed timing gears/chain. no matter how low the miles the teeth deteriorate with age.

I rebuilt the 360 in my friends 72 fury wagon(no oil pressure), he replaced the broken timing gears about 4 years before this.

Those scratches in the bearing are from debris in the oil. How did it get there if you have a filter? Simple, the bypass opened and let unfiltered oil by. Why? Dunno, could be going too long between filter changes, could be defective or cheap filters, could of even been from poor cleaning during the build.

If you aren't seeing copper thru the babbit (the silver looking babbit material is softer than the crank so that debris will score it and not the crank)then I doubt the bearings are the low oil pressure culprit.

Out of curiosity, did anyone mention the oil pump drive? If the shaft is not pinned to the gear it could be slipping. Higher RPM's would aggravate this.

I remember a while back FRAM had some problems with their filters... That is why RapidRobert said non FRAM filter. I suspect the filter also..

You would have to drop the crank to get a mic on it, so plastigauge it, if clearances read good I would change the bearings because I'm there,but maybe not. Maybe just a high volume oil pump. Most don't like high volume oil pumps on this board because you can run your pan empty and they pull extra hp. I have done exactly that but that was a one mile race with 4.30 gears 7200 rpm for a long while.
I would button her up and run it with the for mentioned high volume oil pump and non FRAM filter. With your limited 5000 rpm and truck pan I would run it.. I have done this to a couple big blocks and one small blocks non of them expired due to bearing failure or lack of oiling.

now that the filter is mentioned. I did not have this problem before the fram filter was on there. I have had a few people advise me not to use the fram filters.
I know there was enough oil in the motor and it wasn't low. I don't know if there could be a problem with sludge slowing it draining back to the pan. are there specific areas I should check?
It didn't look like the pickup was clogged , I even blew air through it after I removed it to check and nothing blew out, if it is clogged then its is not something I can see easy.
I did remove the oil pump to change the pickup tube along with the oil pan just before this problem, because I was putting it in my car from my truck , and there was no oil pump gasket there so I didn't put one on when I reinstalled it. but it had good oil pressure for almost 1,000 miles after that.

I did not check the oil pump drive yet. it has never been out of the motor.

I am thinking that I should plasigage the crank, to see if there is an issue there. and since I am in this far in would there be any reason not to put new rod and main bearings and oil pump in?
and since I am almost sure the heads have never been off the motor since new and its blowing a little smoke I should pull the heads and have them redone, hone the cylinders and put a new set of rings in. I have heard that the cam bearings normally don't go bad, it there any truth to this? it still has the original cam in it and I would be ok with letting it there if there is no reason to change it out.

I also don't want to put new bearings in and still have an oil pressure problem. but I am not sure how to know if I fixed it with out putting it back in my truck and running it.
i will plastigage it , check the oil pump drive and look at the pickup tube again.
how would i check it good for sludge causing the problem? is there a way to flush it out while its on the engine stand?

i checked the crank bearing clearance. it was .003 . does this sound safe on a 76,000 mile stock 360 ?

Since it's been 5 years, and you don't seem to be considering a rebuild (that's fine), I would recommend the following:

1) replace the pump (not that it's the problem, but you have it apart and small block oil pans are a pain to deal with in the car)
2) find a baffled SB oil pan
3) install a windage tray

Put it back together, don't run a fram filter, and experiment with heavier viscosity oil if need be. ALSO....running a half to a full quart over may also solve the issue, which is fine as long as the level is below the windage tray.

This is more than likely non related to your issue but the 360 my dad had in a 91 truck was doing exactly the same thing. Pulled the pan and there was next to nothing in the p/u screen. Baffled I pulled the intake and found the culprit. I asked when he last changed the oil. " 10 years or so ago, I just add some when its low I don't drive it that much". The top end of the motor had sludged over all the return passages to the point the oil couldn't get back to the pan fast enough to be recirculated. I left the pan off and cleaned the top end up with kerosene, put in a new pump and its been fine for a few years now.

A 71 360 sludged up so bad there was 1.5 inch piece or carbon/crap length of lifter valley. The looks of that engine I would have just replaced the oil pump with a STOCK oil pump / timing chain gears and drove it that engine lasted another 85K until it was totaled by the guy who bought it

I dont think i used a wrench to tighten the pickup tube, i just tightened it by hand

Awesome topic... Another year, another reply! LOL

cut the filter open see what it looks like

We'll see the answer in 2017 if history is any guide.

For the amount of time this post has taken, I would have torn it down and threw rings, bearings and gaskets in it and been back on the road if there is not too much of a ridge. Tim

I dont get much free time to work on this but i hope i am about done now. I allready junked the filter. There was no sludge anywhere in the motor that i could find. But i did find a busted valve stem seal so i replaced all of them, bolted in a new oil pump and plan on putting it in my 68 D100 this weekend.
It will be nice to have the extra power when pulling a trailer. The old 318 works pretty hard pulling it up hills.

make sure the oil pick up is more then hand tight. i would think it could suck air if not.

I installed a new oil pump and tightened the pickup tube with a wrench this time.
I was replacing the valve stem seals and noticed i had 2 different kinds. One looked like the original ones and the others were smaller . One is the umbrella style and one is the positive style. I got 8 of each in my kit. Any idea why?

Umbrella seals go on the exhaust valves

Ok, thanks. I will be bolting it in my truck tomorrow.

I got to go for a test drive and it seems to be ok. I only have an idiot light for oil pressure but it goes off as soon as it starts. I still am going to put in an aftermarket oil gauge.
Only issue i have is that i think i need a smaller carburetor. I used a 750 that i had but probably on a stock motor a 650 would be better.

Hopefully all is well now. Good luck. BTW, Is the 750 a holley with vacuum secondaries? You should be fine with that with a little tuning.

Yes it is a 750 holley vaccum secondaries. It is just the way it came out of the box. It hesitates a little when i floor it but i did not try adjusting it or rejetting it yet.
Its surprising how well a stock 1971 360 runs with a 4 barrel. The motor has never been apart. Only thing i did was change oil pump and valve stem seals. Its way better than the 318 it replaced.

I put an oil pressure gauge in and it has 45 lbs at idle and as soon as I touch the gas it goes to 60. so it looks like the problem is gone now. only took me 6 years to figure it out lol

I ended up putting a 600 on it and it runs great. Got 87,000 miles on it now. It pulls my box trailer much better than the 318 did. I put an overdrive A833 behind it and it is pretty fun to drive anywhere. It is starting to leak oil pretty bad from the rear of the motor now. Hopefully it's an easy fix.