Low oil pressure?
There is an entire thread /discussion that we had on this topic on the board. You can read yellow rose views on the issue. There are pics posted there showing a chev crank versus the Chrysler small block oiling holes. I agree with yellow rose on the timing issue because I make crankshafts for a living at Chevrolet and I know the position of the holes is very precisely located. However I do not agree with his views on how to improve the timing by cross drilling. Hence the Rehr Morrison article explaining why. But I believe that slotting the bearing shells improves the timing as well as increases the dwell time that the crank has full pressure. Ironically Mopar performance used to sell slotted bearings many years ago.
A friend yesterday tipped me to a very good discussion on small block oiling over on the class racer forum.
360 mopar oiling issue - CLASS RACER FORUM
I only advocate cross drilling a crank to correct the oil timing.
Since you drill cranks for a living, maybe you can shed some light on things pertaining to the oil feed passages in the crank.
If you take a SBC and a SBM crank and lay them side by each, you'll see that they are drilled exactly the same. If you look at the SBC block you'll notice (talking OE stuff here not the later stuff with priority main oiling but it's essentially the same) the oil feed hole in the block is at 12 o'clock looking from the front at the number one main bearing bore.
If you do the math, you'll find that the oil feed hole in the block lines up perfectly with the oil hole in the main journal and the piston would be about 70 degrees ATDC. That is full flow and full pressure to the rod, where peak load is.
Now look at a SBM. I don't have one right in front of me but from memory, the oil feed hole in the blow isn't at 12 o'clock. It's closer to 11:30 or maybe even 11:15 (I used to know how many degrees it was but its slipped my mind but the point is still made) which means, that full flow and full pressure to the rod bearings was too early, long before 70 degrees ATDC. This is because the oil feed hole in the main bearing is in exactly the same location as the SBC crank. If you could rotate the oil feed hole backwards, towards the 11 o'clock position, you would delay full flow and full pressure to the rods until about 70 degrees ATDC.
I've asked everyone from Callie's, Scat, Winberg and one other I forget, and they all said they same thing...you can't move the oil feed hole in the main journal that far back and get it to line up with the correct location on the rod throw.
Is this making sense? It's well established you need full oil at about 70 degrees ATDC. There should be no questions on that. The question becomes how do you make that happen on a small or big block MoPar short of Chrysler changing the oil feed holes in the block, which they did much later on in the R block series, where the adopted a priority main oiling system.
The best answer I've found is to block ALL the oil going to the mains from the passenger side oil gallery. All of it. Doesn't matter how it's done, it needs to be done. A simple set screw in the oil feed gallery from the number 1 main to the drivers side oil gallery will stop oil going there, as you don't need it.
The next step is to drill main caps 1-4 down through the center of the cap, so when the cap is installed, there will be a hole though the cap at the 6 o'clock position. Then, I made some changes to how this was done on the first engine I had. The guy who originated the fix drill a hole in the number 5 main cap on the passenger side directly into the feed passage that eventually leads to the filter. Doing it this way works, but you don't filter the oil going to the mains. The oil going other places gets filtered. So eventually all the oil gets filtered. Then, he made up a right angle fitting that screwed in to the cap. And from there he drilled 4 holes for 1/8 pipe and ran hoses from that common feed to the main bearing caps.
The last thing to do was cross drill the crank. Why? Because the oil timing would still be wrong if you are feeding oil at 6 o'clock but there was no hole in the main journal. In fact, it would be worse that what Chrysler did. Cross drilling simply relocated the feed hole in the main bearing with full pressure, full flow oil at the correct time. I should mention that you have to drill a hole in the lower main bearing shell and use full groove bearings. That way, you initiate flow before the holes line up.
You have now corrected the oil timing. It's simple to hide the system in the pan as it was done when I bought the engine. No one knew what was done. And it worked.
I eventually got tired of seeing trash in the bearings becaus they were getting unfiltered oil. So instead of a 1 inch diameter feed manifold in the pan coming off the main cap, I moved all that crap outside the pan. This also allowed me to run an externally adjustable pressure regulator on the system.
What I did was take a 3 inch diameter piece of aluminum tube about 8 inches long and welded a lid on both ends. On top, I welded in a number 10 fitting, and on the bottom I used 5 number 4 fittings.
Now, I ran the oil out of the block, through my Systems 1 oil filter, out of the filter to the top of my new, bigger manifold, and the five hoses fed each main. 1-4 going through the pan with bulkhead fittings and number 5 being fed right back into the block. I installed my external pressure regulator after the filter and could adjust the pressure to virtually anything I needed. And, all the oil to the bearings was filtered before it went to them.
That, in a nutshell is how I corrected the oil timing. I didn't design it. I just updated it a bit. If you want to turn 8500 and make power doing it, it's what you have to do. No other bullshit works.
So...my question for Duane is...can you move the oil feed hole in the main bearing journal backwards far enough so the oil holes line up at the correct time? With out throwing off the feed hole in the rod? I was always told no, because to me that would be an easier fix.
What do you think Duane?
