I had a similar problem. Following engine biuld I had good oil pressure, then decided to change the oil line union from the block with the correct one (small drilling). I'd left the union location open to atmosphere for a week or so and when I reconnected every thing I had no pressure at the gauge.

I was advised to remove the union again and hand prime the pump by using a pump action oil can into the union location in the block. This back filled the pump via the block gallery. Once re-assembled again when the engine was turned over with the plugs out 55 psi was indicated.

Looks like with the circuit open the oil had drained back past the point where self priming at low speed turnover was acheived. Just a thought.

Dave

HELP !!

I fitted a new pump as the old one had a suspicious crack in it (although i believed it was allright), i took off the pipe at the gauge end and oil comes out when turned over but with the gauge back on i can only get 20 psi, and on running the engine (for a few seconds) it was still only 20 psi.
Any ideas on this, could it be linked to the carbs not set properly and watering the oil down ?
or i suppose it could be a leak somewhere but i can't see anything on the outside of the block ?
Originally i had the block re-bored, oil passageways cleaned and rebuilt back with the crank & pistons in etc ready for me to fit the head and other parts, the rebuild was done by a company that specialise in this so i can't think they have done anything wrong but perhaps i have when rebuilding the rest, can you throw any pointers on this.

Rob

Even fuel diluted oil should show much higher pressure when it is cold.

Did you verify the pump to block gaskets & the pump to intake screen gaskets?

There are a couple of locations where internal oil galley plugs could be missing or leaking, especially if the oil passages were thoroughly cleaned, but it would be a major job to verify now.

DO NOT run the engine even for short times with low pressure. To do so may cause serious DAMAGE to cam, lifters, & bearings. It should build well over 20 psi with starter cranking only. Maybe like 50 psi.

I keep coming back to the oil pressure relief valve plunger not seating. As a test you could put a piece of gasket material between the plunger face & it's seat. Lightly tap the plunger into the gasket, replace the spring & plug, crank it for a few seconds.

I'm about out of ideas on this. There are a few shops that could connect an external pressurized oil supply to the engine & with sump removed, observe the engine internals for amount of oil flow/leakage & make a diagnosis. Not a simple job & very messy.

I see no place where you have consulted with the shop that did the original machining. Maybe time to have a chat with them? Or time for professional "hands on" help.
D

Dave

I tried the gasket on the end of the plunger and that made no difference, however i was a bit nervous about losing the gasket inside the block so did not tap it in place.
So where are we up to:

a new pump was fitted so that rules that out

the pressure relief valve to me seems ok

on turning the engine over the needle on the pressure gauge shows 18-20 psi but is not constant but keeps flickering around 18-20psi

although the gauge was reconditioned i guess this could be faulty (i have known supposidly reconditioned parts not to be correct before), is there a way of testing this or the pressure from the pipe by another method ?

i guess if there was a blockage one of the oil ways then would the pressure not rise higher as effectively it would be pumping against a dead end ?

on looking round the block there doesn't seem to be any visible signs of an oil leak, which i presume if oil was seeping out would obviously cause a reduction in pressure.

would the oil filter have picked up some old residues still in the engine and become slightly clogged up, i guess it's worth a change anyway, i have fitted the spin on canister to mine.

Any more thoughts.

Rob

You can check the gage via another gage (could be an air gage) & a source of adjustable regulated air pressure. Simple air pressure regulators are readily available. The gage works the same whether it is operated by air or by oil.

The leakage I was refering to would be internal. There are several plugs that intentionally block internally drilled passages. This would be impossible to detect by casual inspection.

The spin on filter adapter could possibly be installed incorrectly or be the wrong adapter for the engine. Hard to describe, but the adapter should have a "source" passage that aligns with the outer diameter of the filter & block, & a return passage that aligns with the centeral part of the filter, & block. The two adapter holes must fully align with their respective block holes & the gasket must not block either hole.

An incorrect filter cannister "could" block oil flow. Remember, multiple outer small cannister holes, align so that oil can flow from the outer block hole to these holes. The center oil return hole, filter to block, would be hard to misalign.

There have been several different adapters made. One of the more common is the Moss adapter which uses a K&N # HP2009 filter cannister or equivalent. Not sure which your's might require.

As I mentioned, maybe time to get professional hands on help. It's very difficult to diagnose some problems by mail. If the pressure is truly low, each cranking test that you do is likely to cause damage to the bearings, or especially to the cam & lifters.
D

Dave

I think i have an old air gauge so will try that, also better have the filter adapter off and thoroughly check as well as speaking with the guys that did the recon for their pointers.

Thankyou for your ongoing help.

Rob

[quote=Dave Russell]
The spin on filter adapter could possibly be installed incorrectly or be the wrong adapter for the engine. Hard to describe, but the adapter should have a "source" passage that aligns with the outer diameter of the filter & block, & a return passage that aligns with the centeral part of the filter, & block. The two adapter holes must fully align with their respective block holes & the gasket must not block either hole.

An incorrect filter cannister "could" block oil flow. Remember, multiple outer small cannister holes, align so that oil can flow from the outer block hole to these holes. The center oil return hole, filter to block, would be hard to misalign.

Dave

I just took my adapter off and how it was put on was with the lower "outer" hole that goes to the pump aligning with the center core in the filter, is this correct, previously when i looked at it i didn't believe it could be put on wrong. However on looking at it now if i turn it then the lower hole from the block feeds the small outer holes in the filter with the center hole from the filter going to the center in the block, if that makes sense !!
I believe this is what you described above, please can you verify before i bolt it back on.

Rob

Rob,
Yes it makes sense. If the filter flow is backward, most cannisters have a one way valve that prevents oil from flowing out the outer circle of holes. Anti drain back valve.

The hole from the pump MUST feed the outer circle of holes on the filter.

Hope the puzzle is finally solved.
D

Thanks Dave, yes hopefully that may have solved the problem, what a dope heh !!!!!