No oil in filter after 5 dyno pulls, but excellent oil press

Had 1968 340 engine rebuilt and run on dyno. Engine ran beautifully with 60 psi oil pressure. Ran 5 pulls to dial it in. When I went to dump oil and change filter, I noticed oil filter was bone dry. I pulled oil pan, windage tray, oil pump and rear main bearing cap to see if any plugs were missing causing bypass to occur. Everything looked to be in place. Any suggestions would be appreciated. Thanks...... Mark

Maybe the plug under the rear main was driven in to far?

the plug should be 7&1/4" down in the oil sender rear top of the block port boss (iirc) (I can check tomorrow) which is inbetween the 2 horizontle oil passages that go to/from the filter boss which keeps the oil from going straight all the way up (unfiltered) to where it makes a 90 deg into the main gallery & that vertical passage also continues up further vertical to the oil sender port. the plug in the vertical passage in that sweet spot of several vertical inches makes the oil turn out horizontle & go out to the filter then back from the filter in the other horizontle passage then it hits the vertical passage & turns up a 1/4 turn & goes up till it reaches the main gallery where it makes a right turn into it. if the plug is in the wrong spot all flow would be blocked & there wouldn't even be any psi at the port (oil or air) & you did have pressure. if the plug was forgotten you would have psi & the filter would be full (tho the eng oil would not be filtered & no one would ever know it until the engines' early demise years later & on teardown they find there is no plug). that is strange cuz you had either oil or air psi pressure at the top port so there was an unobstructed flow. I would start by pulling the inter gear & drill prime it with the 5/16" hex priming tool & see what you see. keep us updated this is interesting! PS I'm wondering if there is no plug if the oil rushed up vertical & no or very little trickled out to horizontally the filter but I'm skeptical of that but I would think there would have to be some flow. EDIT pic added. MORE EDIT I reread your post & I'm thinking (now) that the plug was missing & it was getting unfiltered oil & it was indeed going straight up as I would think if the main gallery was not getting oil that it would not have lasted 5 dyno pulls but I ain't a dyno guy soooo I ain't sure. Any thoughts? & the lifters would have been clattering if hyd. MORE EDIT the pan is off so pull the #4 cap & see if the bearing is starved (I bet it ain't). stick a rod into the top oil sender boss hole & see how far down it goes.

Hmmm.. This just gave me an idea for free hp. One less bottle neck.

Water, oil, any liquids, and electricity will take the path of least resistance

I don't know what I was thinking when I posted this. If it was driven in to far the engine wouldn't get any oil but the filter would. My oldtimers is showing up.

my plug is out I checked today on a bare block & 7&3/4" (instead of the 7&1/4 I remembered) down from flush from the top block oil sender boss is in the middle of the 2 horizontle passages.

That is NOT fully correct. All available paths will see flow, the path of least resistance will see the MOST flow.

It turns out that Wikipedia has a page on just this subject. Sooo, I'm going to take the 'path of least resistance' and just post a link: https://en.wikipedia.org/wiki/Path_of_least_resistance

Perhaps the check valve in the oil filter is enough to prevent any flow through the filter given no pressure differential? That's if the plug is missing. I agree on the priming tool test method both with and without filter. And thanks for pointing out that you can check the plug from the top!

Gents,
After several days of diagnosing this issue, my engine builder had a revaluation. After the Dyno, he had brought the engine back to his shop for some minor clean up. He had recalled removing my filter to get it ready to install a 90 deg offset filter housing and did me a favor and removed the filter and spun on a new filter. He had been sooooo busy that he forgot, even though he helped me pull the pan off and rear main cap off to verify presence of the cup plug that diverts the oil to the filter. I did measure the 7 1/4" dimension from the top of the "stove pipe" and it was all good. I was thinking it was something in the filter drain back check that prevented the filter from filling up with oil. It was a WIX filter and I was searching online for possible defects, but found nothing. Thanks for all of the feedback! Believe me, I wanted to strangle him, but he is an awesome guy and friend of mine. Hope you guys got a good laugh on this one.

So what your saying is the new filter was put on and not ran?
If so, good If it was ran and there is no oil in it NOT GOOD
One of my SOP is to always change the oil and filter after 20 to 30 minutes run time on all my new motors on the dyno or running in the car and cut the oil filter open to check for debris in the pleats
New motors make metal, valve springs rubbing against the retainer and against each other on dual springs and so on. It is not possible to keep a motor too clean while assembling them, even in a clean room with clean suits I found a eye lash in one oil filter
BTW, I highly recommend pre filling all oil filters before installing them

we ain't laughing, we're here to solve problems & we've all been "there" (& worse). I measured my bare block & 7&3/4 not 7&1/4 is in that sweet spot of several inches of vertical passage inbetween the 2 horizontle passages that the plug needs to be. I will check closer tomorrow. there is a range a bit on either side of 7&3/4 but when I went 7&1/4 down the other day to check on the 7&1/4 I posted, 7&1/4 did not even reach the top horizontle passage so I went further down & 7&3/4 was in that good range. I will confirm for sure tomorrow. What Cab said, if the plug was missing then it dynoed 5 times on unfiltered (but new) oil which is much much better obviously than the passage blocked off somewhere along the line with the plug in the wrong place (other than the correct sweet spot) & it was not cuz you had psi.

Cab,
The new filter was put on after the run in, but not communicated to me. Lol It caused some confusion with me having to check for the plug that directs oil to the filter. When I checked and it was there, I shined a flash light through the 2 oil holes where the filter mounts and checked the top pressure port to make sure plug was not blown through. After that I was suspecting a defect in the filter. But still, there would be some trace of oil in the filter being that the oil enters the filter through the outside 5 holes and enters the engine through the center. In summary, my engine builder had industrial amnesia. Lololol

Rapid,
I will double check that 7 1/4" inch plug dimension. I think ther is some forgiveness between the bottom hole that supplies oil to the filter and the upper hole which supplies oil to the engine (oil out of filter). I don't believe there is a shoulder that the plug is driven in to from the bottom of the block. It just needs to be in the center of the 2 holes.

Thanks Again for all of the great help!!!

Sure would have been nice if he primed it

Fill it now before starting it or prime it before starting it up again

I checked closer today & measured 7 & 31/32" down from the top threaded boss flat will put it squarely in the sweet spot inbetween the 2 horiontle passages.