My 327 blew up!!!.....or did it?

[midnight sun]

A few weeks ago I posted regarding my concern with the low oil pressure on the 327 in my A.  Got a few responses and most said it wasnt/shouldnt be a big concern.  (This is a rather long post).



WEELLLLL!

Today we were going to go to a show and shine about 70 miles away.  Ive got about 500 miles on the motor now but only in 10-15 mile spurts.  About 50 miles into the trip I noticed the oil pressure dropped about 3-5 lbs.  At the same time, I started hearing a very faint knock.  I let off the gas and it became fainter.  I gave it a little gas again and within 10-15 seconds the knock grew progressively louder and the oil pressure dropped toward zero.  I shut her off and coasted to a stop.  We checked the dipstick and it appeard to have no oil on it.  No sign of an oil leak anywhere.  Everything was dry as a bone and the exhaust pipes were black but dry.  I checked the oil last night--Full.  We put two quarts of oil in it and started it up and still had the knock.  It took me 3 hours to go and get a trailer.  Just for  kicks I again checked the oil and it showed overfull by at least a quart.  Since my wife was the only other person there and we couldnt push the car onto the trailer, I decided that since I had already probably spun a bearing, I couldnt do much more damage so I fired it up to put it on the trailer.  Surprise Surprise, oil pressure went to 30 pounds and the motor was as quiet as a mouse.  No knock , no nothing.  I got it home and fired it up again to back it off of the trailer and got the same result.  30 pounds and no noise.  There is not much doubt in my mind that I spun a rod or main bearing but why would it  magically heal itself?  Then Im trying to figure out why I it appeared there was no oil on the stick.  Maybe because it was so hot, it ran off before we could pull it a get a good reading?  But why was the oil so hot?  Then Im asking if I had 5 qts of oil, why did I lose pressure?  Bad pump?  It is a new Melling high volume.

Guess I will pull the pan and check the bearings but Im still stymied as to why and what happened.  The water temperature never got over 200 degrees.

Any thoughts??

TIA

Later

[phat46]

Maybe plugged oil return passages? pumps all the iol up top, but it takes along time to return to pan?...just a thought.

[enjenjo]

Maybe plugged oil return passages? pumps all the iol up top, but it takes along time to return to pan?...just a thought.

My thought too.  But it doesn't usually happen on a fresh motor.

[2rods]

What about pickup? If it is too close to pan that can cause lots of problems too.

[Crosley.In.AZ]

the bearing halves in the rod could have spun around and wedged themselves to tighten things back up against the crank...... & the motor is quiet

[Bruce Dorsi]

It's hard to diagnose some problems over the internet.   ......Here are some possibilities:

(1) Oil pump gear slipping on drive shaft?

(2) Pressure relief valve in pump hanging open, allowing pressure to drop?

(3) Oil pump pick-up damaged, restricted, or too close to the pan?  .....Pump pick-up mounted too high in the pan?

(4) There have been reports of high-volume pumps emptying SBC oil pans faster than the oil can drain back.  .....Usually this only occurs at extended high-rpm.

(5) Clogged or restrictive oil filter?

(6) Faulty oil pressure gauge or air bubbles in the gauge line can cause erratic readings.

(7) Loose, missing, or damaged baffles, or non-functioning trapdoors in the sump?
..................................

On a friend's '32, the SBC is mounted with the rear of the engine pointed down more than usual.  ....Quite a bit of oil accumulates in the top of the cylinder head since the only functioning drain ports are at the rear of the head. ....This slows the return of oil to the pan.  .....Driving uphill aggravates the situation.
...................................

Have you checked the calibration of your dipstick, to be certain the stick reads full, with the correct amount of oil in the engine?  ....Is the dipstick tube loose in the block? ....Many aftermarket or modified, dipsticks, and/or dipstick tubes are not correctly marked for the oil pan being used.
...................................

Your oil/no oil readings on the dipstick seem to indicate the oil did not return to the pan fast enough.   ....If there was a fault in the pump, the oil should have been in the pan.
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I've been running a Melling high-volume (with the low-pressure spring) on a 350 SBC using a 4qt pan (+ 1 qt in the filter).  My engine is mounted nearly level, and I have never had a starvation problem, even at 6800 rpm.
..................................

I hope your bearings are intact, Jack.  ... Good luck!

[SKR8PN]

What head gaskets did you use?
Bet you find a couple of misplaced,or undersized, oil return holes in them.......
Pull the engine. you prolly DID do some type of damage to the bearings by running them dry.And by DRY,I mean all the oil was in the valve covers,and NOT in the pan.

[Sean]

Pressure relief valve in the Pump sticking is the the first thing that came to my mind.

A friend of mine just built a new 350 for his dirt car using a big name HV pump. When he fired the engine the first time to break in the cam, he only had 30lbs. He knew that wasn't right, but it was steady, so he went ahead with breaking the Cam in.

20 or so minutes later, when he backed the idle down to where it would normally be (about 1200 rpm), he had around 12lbs of oil pressure.  He didn't want to run it that way, even though they say a sbc will run on 7lbs, so he pulled it back out and put a stock oil pump on it. 60 lbs, right off the bat, and warmed up, it dropped to about 45lbs.

Took the Melling bypass spring out and a broken piece of hard white plastic came out with it. He said the plastic collar on the oil pump drive wasn't missing any pieces, and thats the only piece of white plastic in the engine. He figures it had to come from the factory that way because it was brand new when he put it in, and it went straight from the box to the engine.

Hasn't tried it on another engine yet, but he thinks that piece of plastic was keeping the relief valve from seating fully. Sounds logical to me...

[SKR8PN]

Sean,it sounds like that piece of plastic was holding the bypass open. If the bypass sticks closed the pressure will skyrocket,sometimes to the point of blowing the filter off!. Don't ask how I found that out!

I am guessing Midnight sun's problem is with the oil returns. After running it,all the oil ends up in the valve covers,"starving" the bottom end.Hence,the lack of oil pressure,and no oil reading on the dipstick.Thats also why he had pressure again after it sat for a bit. Gave the oil time to drain back down to the pan. Bingo,oil on the dipstick and oil pressure returns!

[midnight sun]

(2) Pressure relief valve in pump hanging open, allowing pressure to drop?

Bruce,

Is the oil pressure relief valve on a SBC in the oil pump?  I am just curious because I have heard that sometimes the relief valve is in the adapter for a spin on filter.

Thanks

[SKR8PN]

(2) Pressure relief valve in pump hanging open, allowing pressure to drop?

Bruce,

Is the oil pressure relief valve on a SBC in the oil pump?  I am just curious because I have heard that sometimes the relief valve is in the adapter for a spin on filter.

Thanks

Still doesn't explain the NO oil reading on the dipstick when the knocking began.............then,the oil  magically returns?
Only thing that can cause that, is all the oil being pumped into in the valve covers,and not draining back fast enough

[Sean]

Is the oil pressure relief valve on a SBC in the oil pump?
Thanks

This is a BB Chevy Pump, but you get the idea.  There is a spring in there that holds pressure on the valve. Some oil pumps come with a couple different springs so you can adjust the point at which the valve starts bypassing.

[Pep]

(2) Pressure relief valve in pump hanging open, allowing pressure to drop?

Bruce,

Is the oil pressure relief valve on a SBC in the oil pump?  I am just curious because I have heard that sometimes the relief valve is in the adapter for a spin on filter.

Thanks

Still doesn't explain the NO oil reading on the dipstick when the knocking began.............then,the oil  magically returns?
Only thing that can cause that, is all the oil being pumped into in the valve covers,and not draining back fast enough

Sounds kinda logical to me as well..Easy to prove. Just take the breather/filler cap off then fire it up. It should fill up fairly quick if its a drain back issue...and quite visible.

[midnight sun]

Sean,it sounds like that piece of plastic was holding the bypass open. If the bypass sticks closed the pressure will skyrocket,sometimes to the point of blowing the filter off!. Don't ask how I found that out!

I am guessing Midnight sun's problem is with the oil returns. After running it,all the oil ends up in the valve covers,"starving" the bottom end.Hence,the lack of oil pressure,and no oil reading on the dipstick.Thats also why he had pressure again after it sat for a bit. Gave the oil time to drain back down to the pan. Bingo,oil on the dipstick and oil pressure returns!

Sounds logical to me too except I have run this engine for around 500 miles.  Granted it has only been for 10-15 miles at a time but I would think that would certainly be far enough  for it to do what you have suggested.  Yesterday the only difference was that I ran constantly for about 50 miles before everything went gunnysack.

[Bruce Dorsi]

....<snip>...  We checked the dipstick and it appeard to have no oil on it.  No sign of an oil leak anywhere.  Everything was dry as a bone and the exhaust pipes were black but dry.  I checked the oil last night--Full.  We put two quarts of oil in it and started it up and still had the knock.  It took me 3 hours to go and get a trailer.  Just for  kicks I again checked the oil and it showed overfull by at least a quart.
   
...<snip>...Then I'm asking if I had 5 qts of oil, why did I lose pressure?

==================================
Jack, if you started with 5 quarts, ran 50 miles, added 2 quarts, and registered 1 qt over-full, that would mean you lost 1 qt in 50 miles of driving! .....That is an excessive amount of oil to lose.

Have you had to add any oil in your first 500 miles of driving, other than the 2 qts you just added?

If by chance, you started with less than 5 qts, or lost 1 qt while driving, the lower oil level will allow the pump to empty the pan quicker if the drainback is slow.

If indeed you lost 1 qt in 50 miles, where did it go?  ....You mentioned no sign of leaks, and a black, but dry, exhaust.

Let me tell you a story. ....I'm not saying this is your problem, but it's food for thought.

A friend was using 1 qt of oil every 100-125 miles in her 383 SBC. (She bought the car without knowing of this problem.) ....The engine ran fine until a sparkplug would foul with oil.     ....There was absolutely no sign of smoking on start-up, acceleration, deceleration, or steady-state driving. Absolutely no leaks present, and the exhaust pipes were black, but dry!  .....Hot & cold compression tests and a leakdown test proved good condition of the rings and valves.

She was ready to buy a new crate motor, when I suggested changing the valve seals first.  ....Everyone told her it was a waste of time, but I finally convinced her she had nothing to lose but the cost of the seals, if there was no improvement.

As her husband and I removed the seals, we found all the umbrella-type seals that we removed were in good shape. .....It was then that I noticed that because of the angle the engine was mounted, the rear two valve guides on each head were submerged in oil, before the oil would reach the rear drain port.  ....After asking, I learned that the #7 & #8 plugs were the ones that would foul.

We installed positive-type valve guide seals on both the intake and exhaust valves. ....Fortunately, the o.d. of her valveguides were machined when new.

With the new seals in place, her oil consumption and plug fouling stopped completely.  .....It appears that the umbrella-style valve stem seals were actually acting as a "pump," forcing oil DOWN the guides, since they were submerged.

....It's hard to believe, I know, but I kid you not!

Sean answered your question in an earlier post, about the pressure relief valve being located in the oil pump housing.  ....That is correct.

I believe the pressure relief in the oil filter mounting which you mentioned, is to allow pressure to bypass the filter if the filter becomes clogged.