Mine had the cone shaped plunger, not the ball, but the tapered surface of the cone and mating taper in the block are visually undamaged. I wonder if a ball would seal better?

Changing from my break-in oil (cheap Walmart 20w50 plus a quart of Redline breaking in oil with moly and Zinc) to Valvoline VR1 last night gave me most of my pressure back. Still need to find the rest of it as I don't want to be stuck down in the 15 psi range when the car has 60k miles. 

Maybe the seat for the pressure relief 'ball' is damaged.

I ordered a pin drive pump for my car (GLP142), but it was clear looking at it that the shaft was way too short (about 3/4" too short).  The shaft diameter of my old pump was the same as the new one, so I pressed out the shaft from the new pump and in went the old longer shaft.  It works fine and comes up to pressure - however it is interesting that my pressure is lower by about 7psi than it was previously. Clearances are all tighter as it has new main and rod bearings, cam bearings, oil pump, gaskets on oil pick up and o-ring between block and gearbox casing, etc.  Screws holding pump are short type that don't go through.  I brought it back up by adding a few washers behind the pressure spring. 

Steve, I think he will probably be pulling the engine out and disassembling it again.  But before that happens, I was just trying to think of anything external that could be checked/replaced, what the heck see if it helps.  Taking the bypass out means one less variable.

I have a block with a cracked center web.  Oil pressure was fine at cold idle, got worse as it heated up, much worse when the engine was pulling a load.

I was reading a Keith Calver article yesterday and he mentioned oil pumps bypassing due to the oil pump bolts bottoming. Just slightly too long and the oil pressure will lift the pump from the block and cause it to bypass "internally". I haven't thought about the results of bottoming bolts but I always check the thread depth on the oil pump before installing. Just a thought.

Kelley

Still thinking, not sure how you think the oil filter by pass works. The way I see it when the filter stops flowing oil the by pass opens and allows oil to by pass the fliter and feed the engine directly. I'm having a real hard time with the higher rpm lower OP thing. Thinking back I recall something like this. Customer was installing a timing chain kit on a Ford. To avoid getting gasket material in the oils pan he stuffed shop rags around the front edge of pan. This was an in car change. As it turned out he left one rag in the pan. when it would get sucked up against the pickup the pressure would drop way down. We dropped the pan to check oil pump found rag reassembled and all was well.

Steve (CTR) 

OK so you have the canister type.  I could go pull one apart to check, but I am pretty sure the filter housing has a bypass valve, this would be my suspect because you have checked everything else.  My working theory is different from Steve's,  I wonder if instead of leaking oil somewhere internal to the engine, could the filter housing be restricting oil flow?  The pressure to the gauge is measured in the main oil gallery after the filter, low pressure there could be low due to an internal leak, or due to insufficient supply.

I think the oil filter housing can be modified to block off the bypass valve, but my suggestion would be to substitute a full-flow (no bypass valve) spin on filter housing with a decent modern filter, like the Bosch 72150.

Hello scooperman. the 1300gt has the original oil housing held on with a with center bolt and uses the old style paper filter element.

 

 Thanks Bruce

Hi thanks for the comments - the spring and ball are new ( approx 12 months old )  after we found that the old relief valve cone and spring were sticking in the housing.

 

 Any ideas are welcome

Did the 1300GT have a spin-on filter?

It does sound extremely strange that increasing the rpm makes the pressure drop. I would not think the type of oil would make that kind of difference. Could it be something with the spring for oil pressure relief valve? Maybe it is weak and as the engine revs trying to make more pressure the spring is compressing more than it should when hot and thus relieving pressure instead?

(Even to me it sounds like just fishing with that idea.)

Our old girl in a sorry state

Thought you chaps might like to see what pulled up outside my place yesterday GRX310D - real works S

Agreed-  Will inspect the relief valve seat under mag glass ( if possible ) tomorrow night .

If I recall correctly years ago we had a OP problem with a pin drive cam. Seems to me the pin had come out of the cam. I don't think that would apply here. But rev up, preasure down is not normal.

Steve (CTR)

Hello Steve thanks for the comments , as you can imagine we are totally dejected. It took approx 4 hours to get the engine and box out . We obtained the new shells within 12hours and had the engien rebuilt for refit by the following night. Another 8 hours saw us refit and spin over the engine to get 80/90 psi on the started motor . Fired her up today and the rest you know .

 

 back to detection - If the oil pump can give 80/90 psi then I think the problem cant be here. It seems to be heat related so the oil is bleeding away as viscosity drops  . Don't think it can be main or big ends , we did not measure the cam bearings but why would they bleed so much when hot?. Concerned that I have a cracked block and the gap opening up when warm !

 

 best Regards Bruce

Hi thanks for the comments - when engine restarted the tick over was high at 2000rpm - and when the engine was hot/warm the oil pressure was about 50 but if I rev to say 3000 then she starts to fall away again. Note this is with all new shells

 

 best regards bruce

Bruce, really sorry to hear this. Myself I'm chasing a run hot thing and it seems to mess with oil pressure as well. But back to your problem I was thinking last night and ask myself if a supply side problem why so high a pressure cold? It's clear we have an uncontroled oil bleed. There are only so many places we have controlled bleeds. There is pressure oil to the front cam bearing which sends it to the head and rocker assembly. Each rocker bleeds a little. You have pressure to #2 cam bearing it like #1 bleeds a little but goes no where else. Mains # 1 # 2 # 3 bleed a little due to clearance. Then the rods are fed and bleed due to side clearance. The last time I ran into something like this (not mini) we built a stand mounted the engine less pan and pumped oil in under pressure and spun engine with starter and looked up inside to see where and how much bleed we had. Had a big catch pan under. Connected to hot water heater and ran full hot water with a slow exit valve. Pull valve cove while ruiing and see what's going on under there. Missing plug in the end of rocker shaft mabe a missing plug in the back of block behind clutch housing. If the front one leaks it goes in floor. Keep me in the loop.

Steve (CTR)

What rpm is the engine at when reading the 40 psi hot? I am used to seeing 25 - 30 psi hot at idle as considered normal for a street car. Some of the racing/autocross folks I know in MOT prefer 40 psi hot at idle in their race cars, but seem to agree that the 30 range is fine for a street Mini.

The hot pressure should go back up to over 50 as the rpm is increased to cruising range (about 3500-4000).

Hi - should have said 0.001" max  ovality on center main bearing on crank during inspection.

 NOT 0.010"  !!

 

Finger trouble