lifter galley crossover tube
OK verbatim: "In an effort to find out why this main, which is not far from the oil pump & should logically recieve plenty of oil, was being slighted, Larry spent considerable time forcing high water pressure through the oil passages of a block to see how it was being distributed. What he found was amazing: the oil was actually going through the main oil gallery on the right side "too fast" (in italics). Since the mains are fed from the right gallery through passages that meet the main gallery at right angles, the pressurized oil couldn't make the sharp bend very easily". He went on to say that there is no problem if the RPM is 7500 RPM or less.
You know I was thinking about this post today at work and I remembered an experience I had a few weeks ago.
I own 1996 Dodge Ram diesel. As many of you probably know these trucks are notorious for the top of the dash to crack and fall apart.
I bought a new dash top and installed it a few weeks ago.
The biggest challenge with this job is to remove and reinstall the distribution "tubes" that are screwed to the top of the dash.
These tubes distribute the air flow to the defrost vents and the dash vents.
To get the top of the dash off the frame required removing many other items including the dash bezel. This bezel, when you remove it takes the air deflectors off of the air vents with it ,on the drivers side. Louvres are the things that aim the direction of the air coming out of the dash vents.
The two louvres (hope I am spelling that correct) on the passenger side did not require removal.
Once I had the new dash top bolted back on to the distribution tubes and the dash fastened back to the truck, I knew I was on home stretch with this job. Only the bezel and a few other small items to finish the job. It was very hot that day and I decided to start the engine and turn the air conditioning on to have a break and cool off.
As most vehicles do, the blower motor is located on the far right side (passenger side) of the distribution tube.
When I turned the blower motor on to its highest speed, I got a gust of wind coming out of the two drivers side vents at a force that I was not used too. What the heck was going on. Did I hook something up wrong?
I began to feel around with my hand and noticed that almost no air flow was coming out of the passenger side two vents. Almost nothing.
I continued to finish the rest of the job not knowing why the air pressures were uneven side to side.
When I put the bezel back on which includes the air deflector vents,
I turned the blower motor back on and low and behold the distribution was even again. Air was now flowing out of the two passenger vents.
Not totally even but at least you could now feel air pressure.
What does this have in common with our la small block?.
The high volume pump and the blower motor are on one end of a round tube or a round galley.
In stock form both galleys had a large leak at the extreme other end.
When that leak was present in the dash tube, the air ran almost completely by both passenger side vents. Why? Because of the large leak on the end of the tube.
When I put the drivers side air leuvres back on I introduced some resistance and slowed the velocity and forcing some of the air to flow to the two passenger side vents.
These two vents on the passenger side are closest to the blower motor and yet with no resistance on the other end farthest from the blower, little to no air flow would come out.
Does our stock la motor have a big leak at the other end of the pump?
You bet it does. The Passenger side galley is being asked to feed 6 lifter bores, before it even gets to the end. At the very end the galley is being asked to feed #1 main bearing,#1cam bearing,#1 rod bearing,and 8 more lifter bores. This creates the huge leak just like the removal of the leuvres on the dash.
The result,? The oil runs right past the two closest main bearings to the pump, just like the dash vents did.
That is why in one of my previous posts that I believe that the plug at the end of the galley is just as important as the crossover line.
With the plug in the end of the line, the oil that makes it past the crossover line only only has 3 leaks to feed instead of 11.
