Hi All,

Some of you may remember my post about Low Oil Pressure a couple of weeks ago; there is a recap of what happened after
these few questions:

1. What Path does the oil take once it enters the pick-up (This is
an L98 Block from the early 70's)?

I'm assuming it routes through the pump, down the center of the
oil filter, exiting the tiny holes arond the circumference of the
oil filter, then back into the engine block?

2. The oil filter adapter has a spring loaded "vavle" next to the
threaded filter adapter. Is this a pressure vavle, or a fail-safe
device in case the filter gets blocked? The valve seems to open
under pressure so I'm assuming it's a bypass valve if the oil
enters from the center of the filter first?

3. Are there any other oil sending bores in an early model small
block other than the one behind the intake manifold, adjacent to
the distributor? I'd like to check pressure from another spot on
the block in case my initial sender bore is blocked with debris.

4. Lastly, with Hydraulic lifters and hollow pushrods, roughly how
long (in seconds) should I wait to see oil pumping into the rocker
arms? I have removed one of the valve covers, but I have yet to
see oil traveling to the top of the heads.

Thanks for any help. Read below for the history.
Tino

>>>>>>>>>>>>>

I've been able to perform a few tests on the car with the conclusion
that my oil pump is faulty.

Using a drill to prime the pump, my mechanical gauge showed
20 PSI. I'm not too sure what the RPM of the drill was, but it
doesn't matter. I just wanted to prove that the oil could get
sucked up into the block .

After some fighting with initial timing, the car fired up and idled
very nicely. The oil gauge showed less than 10 PSI at 800 RPM.
I'm used to seeing close to 20 PSI. I swapped gauges thinking
the original was broken - same outcome.

No matter what RPM the motor rev'd to, the oil pressure did not
climb above 10 PSI.

I shut the motor down before reaching 2000 RPM to avoid severe
damage. In total the engine has been run for about 30 seconds
at a max of 2000 RPM. THe bearings were lubed during the rebuild
and there was some oil pressure throughout. I hope the bearings
and crank are not damaged.

 

It comes up from the oil pump, through the main cap, at an angle up to the oil filter boss, where it comes in horizontally. From there it goes into filter around the perimeter, comes out the center, up into the passages.

The valve in the adapter is a bypass in case filter gets plugged. It won't affect pressure.

If you think sending port is plugged, just pull the plug there, disconnect coil, crank for an instant and oil will geyser out of there. Did that once by accident, with coil hooked up. Was cleaning that boo boo for a while.

 

you are mostly correct, the by-pass is for
when the oil builds to much pressure when cold.
oil comes back into block and heads to above the cam shaft bearings, around the cam bearings to the main bearings.
there is another pressure port at the front of the block, just above the timing chain cover, alittle to the pass. side.
but remember the pressure will be slightly lower at this point.
as to how long it takes for oil to reach the rockers, it all depends on weight of oil, temp. of oil and how much pressure your pump puts out. on a warm summer day with say 10w30 on a cold engine i have seen it take about 4 to 8 seconds to reach the rockers.

 

The oil pressure is regulated by the spring in the oil pump itself. One common problem that could cause this situation is improper cam bearing installation.

 

Thanks for the clarification.

It seems I'll be buying a new oil filter and some thinner oil tonight.

If the oil change can't restore pressure...up comes the motor again!

The cam bearings were installed by the pro-shop. The block was
hot tanked and prepped by them as well. I rebuilt the entire
motor and checked clearances with plasti-gauge and a micrometer.

All were within tolerance 0.0015" to 0.002"

At this point, I'm hoping it's oil or the oil pump. I'd really hate to
chase a clearance issue, or blocked oil passage in the block.

Keep you all posted. Thanks for the input.