Things were going great right up until they didnt...

10W30 VR1. It did get quite hot and that's when we noticed oil pressure dropping

 

Here is run 4, with hot oil, 45 psi at 5000.


Here is a run 2nd from the last.



Saw some in the middle with 55 psi or so at 6k. I finally would only start a pull with cool oil but by that time I think damage had been done

 

That pressure is fine for SBC but no way for a BBB. Should have never ran the pull.....gotta have min 70 at 6000 at front of block.
I had that kind of pressure (less than 60) and ended leaving lots of HOT parts on the track at Quaker.

 

Running "cool oil" for decent OP numbers should have been a huge red flag! You have a clearance or an assembly issue.

 

Right....pressure at 200 deg would of course been even less. 20w-50 would have saved motor but something else not right. Those clearances not out of norm.
What relief spring was used? I have shimmed Stage 1 spring before but TA adj way to go.

 

Sorry to hear the problem, I am interested in learning what will be found given a future 430(?) engine I'd be assembling.

With what I read so far, it appears the oil pressure was low on the latest pulls. Was the pressure (relatively) low during first pulls as well? If a deterioration was noted over time, was this continuous or in the form of a "step change"?

For a properly assembled engine in regards to clearances, it sounds like oil pressure is "excessively bleeding" somewhere else - as before said, possibly relief spring pressure / lifters and/or others?

I am not familiar with the practice of using different clearances as mentioned on purpose, i.e. "7 and 8 were .0023, the other rods were .0025 to .0026". That level of difference is not very material in my belief if oil pressure AND flow rates are sufficient. However, from first principles, I'd say oil would have a chance to bleed from the 1-6 before getting into the smaller clearance of 7-8 and therefore, 7-8 may starve on oil at boundary conditions. I would not use the staggered clearances as mentioned - or, if machined like that, I would have it assembled the other way around. The phenomena being described is a fact but if its effect is material enough to be a consideration is beyond my experience on the topic... I am happy to be lectured nevertheless.

Cheers/Alex

 

What I am most concerned with is the oil pressure at peak torque... that is when the motor has the most load on the bearings...

40 psi

JW

 

And Scott is tr0ublshooting his oiling system.. in a failure situation like this, it's important to test for a massive oil hemorrhage before you take it apart.. but after you seal up the damaged rod journals.

It's been my experience that large bottom end clearances, loose lifter bores, and other other bleeds will show up mainly at idle.. once the oil pump is spinning fast enough, it will typically work at the pressure the relief system is allowing, as long as the suction side and the pump are up to snuff..

So we are looking for a stream of oil coming from somewhere. Main, rod, and cam bearings clearances, even "big" ones, just drip, drip, drip off the bottom end.

I have seen broken blocks be the issue, where a cam bearing walks out, and uncovers the oil passage behind the bearing,

JW

 

Here is a pic of the test setup



And a link to the video of the results



This was 0W20 synthetic at 57 deg F

 

Did the pressure slowly drop on the gauge after priming or drop right away? I had an incorrectly installed cam bearing and had noticed the quick drop and investigated.

 

My ‘78 350 block had casting porosity in the passage feeding number 5 main. I discovered it running the pump with the drill with the intake off, boy that somBitch was wizzin, I sealed it up with JB Weld

 

So the cast iron iteself was porous enough to leak pressure? That's crazy. How could it have run from the factory (assuming it did). Nice find! I wonder if some kind tiny cracks might have contributed...

 

That was on my last build before my current one, I bought the engine from the Junkyard and I noticed it had a hi volume pump on it. Funny thing is o drove the car after the build for years, even down to the GS mats, hot idle pressure was 20 lbs on 10/30 oil WITH a standard volume pump

 

I had the blue or green spring and saw 70 psi on initial start up at around 2500 rpm

 

I had 56 psi on initial startup on the engine stand at idle, room temperature oil. Quickly went to 70 psi with a quick blip of the throttle, may be 2500 rpm or so.

Looking thru the data sheets, notes, and videos, after initial break in, pressure had dropped slightly but stayed consistent until almost the end during the pulls. I never saw 70 psi again, but never did rev it until oil was warm

After break in idle at 128 deg F oil was 30 psi. At 177 deg it was 27 psi.

Here is oil temp and pressure for runs 8, 20 and almost the end

 

Hate to tell you but I would have pulled the plug on the dyno with pressure like that......

 

Bearing shell thicknesses were measured and arranged to produce the closest clearances at the front of the motor, the loosest at the rear. The rod housing IDs were very consistent, the crank rod journals, however not so much. So the clearances were juggled and are "as good as it gets" (for me)