I use a 0W-40 during cold weather and 0W-60, when you can find it, during summer months. When the 0 grade oils are hard to find I substitute a 10 weight alternative, i.e. 10W-40.
Your
oil clearance will in large part be determined by the bearing clearances on the rods and mains. The
oil system is essentially a controlled leak. Like a garden hose driving two sprinklers the total nozzle area of the two sprinklers and the hose's water pressure determines the total water flow. If one sprinkler has more nozzle area it will artificially lower the hose pressure supplying a reduced pressure and volume to the sprinkler farther away.
The same is true of our rod and main bearing clearances. Rod bearings are oiled off the mains and the mains get first dibs (so to speak) on the
oil from the main oil galley that is delivered to the engine. Like the single hose with two sprinklers the mains are that first sprinkler in the oiling food chain. What ever does not leak out the mains is directed up through the main to rod oil drilling in the crank for the rods.
Tightening up clearances on the mains drives more oil to the rods and less to the mains and vice versa. A good rule of thumb is 0.0015" to 0.002" on the mains and 0.002" on the rods with a sufficiently high volume pump and high pressure relief spring so that everybody gets an adequate volume of oil to support the hydrodynamic wedge that protects all the rotating parts.
My engine is a modern aluminum block OHC variety so I have all the challenges we have already spoken about and I also have to keep four cams lubed so I don't kill cams and heads. My cold main clearance is 0.0015" and my rod clearances are 0.002".
At first glance it would appear Ford attempted to force more oil upstairs with the tight main clearances. The growth of the aluminum block after warm up makes the main clearance comparable to a cast iron block at operating temp.
Melling has a good video that tells the story of bearing clearances and oil flow, click here =>
Melling on Clearance and Volume
My pump is an aftermarket gear pump from Raceline (
Racelinepumps.com). I use a pump gear that is 1.45 inches long. The pump is driven at about half crank speed. I also use an external pressure regulator to regulate the oil pressure to about 70 psi at idle and about 130 psi or so at 7000 rpm.
I choose the higher pressures to protect the cams and heads which are at the end of the lubrication food chain, so to speak. I always use ProLong for engine protection at cold start.
Ford did not supply these engines with this kind of oil delivery in their original OEM condition. The OEM engines also tend to get a noisy valve train as they age. Regular oil changes and more than adequate oil supply can extend the life of the valve train pieces in an OHC application.
On a pushrod application the adequate oil supply to the top end keeps rockers and rocker shafts in good condition and a quiet valve train again. For years there have been various techniques used to restrict oil to the rockers.
There are two valid reasons to do this. The first is once up there you need to be able to get the oil back to the crankcase. OEM drainback holes can be challenged if the oil supply to the top is too great. The second is, a racing oil pump can pump the pan dry more easily than a standard volume pump. Once the pan goes dry your bearings go away — sooo any oil absolutely not needed like at the rockers would get restricted by installing various size jets in the oil delivery drillings. On drag cars the restrictors arguably might be a good idea. Other applications probably not so much.
NASCAR engines that need to last 500 miles do not use oil restrictors to the rockers. In fact some engine builders flood the rocker covers submerging the valve train in oil both for lubrication and cooling. These engines also have impressive drainage systems to cycle the oil back to the crankcase.
Soooo, big pump, small pump, low pressure, high pressure and oil weight?
For me, I like high volume, high pressure and 0W weight synthetics after break-in. The high pressure costs me maybe 5HP or so to drive the pump but I have way more power than I can reliably put on the ground anyhow.
Ed