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MG MGB Technical - engine rebuild advice needed

Hi all,
After a total rebuild I started my engine with the common procedure.Priming the oil pump, plugs out, fuel pump off and cranking untill there was oil pressure.Then I started the engine and it fired up after a few seconds. So far so good. BUT. The oil pressure is not good. With a cold engine I have at idle 40psi and 50 psi at 2000rpm. After a few minutes when the engine warms up I have 40psi at idle and 40 at 2000rpm.Not so good I would think.
I supposed that the oil pressure at 2000rpm would be much higher untill the moving parts are bedded in.
I was thinking about three possible causes: bad bearings, bad oil pump, bad relief valve.
I do not suspect the bearings because the rebuild was done by a well-knowm rebuilder. I renewed the oil pump by a new one(made in India,quality??) and I renewed the relief valve and spring(made in ?).
So I was thinking, if the bearings are not ok then the oil pressure at idle would be much lower then 40psi.
So I suspect or the pump(I do not trust the in China, India,.. made cr..)or the relief valve that is not closing.
Before I start dismanteling I want to ask for any comments and/or advice.
Thank you,
Herman

H. Jorens

To your list you might add a faulty pressure guage, wrong oil pump gasket fitted, faulty oil filter and wrong rear oil cooler take off fitted

First try shimming out the oil pressure relief valve (OPR) spring.

Undo the cap and put a washer or two between the cap and the spring - about 1/10 inch thick should do fine.

If the oil pressure rises - I would expect 60 - 70 psi cold and 50 psi hot at idle - then it points to the OPR valve.

Second, try a new oil filter - I have known these to be faulty and block oil flow.

From there on it means dismantling to find the cause.

Chris at Octarine Services

Chris thanks for the advice, the pressure gauge I tested and is OK. I will renew the oil filter. But what you mean by "wrong rear oil cooler take off fitted"?
Herman
H. Jorens

Maybe your engine man didn't realise that these engines actually have a spacer under the relief valve spring std. and missed refitting it to the new relief valve and spring--------just a thought
willy
William Revit

Chris is talking about the union that screws into the block,next to the pressure gauge take-off. This union has a tube like bit that fits into a drilling in the block which directs the oil to the cooler and then filter before going into the main oil gallery. Even if the wrong union was fitted the oil system would still pressurise properly but the oil would be un-cooled and filtered. Barneys site has an oil flow drawing somewhere.
A J Dee

There are fittings out there that do not have the tube extension - these allow unfiltered oil into the bearings which rapidly wear from the usual metal swarf from a new engine, it is this wear that drops the oil pressure, ruins the new bearings and crank - so I'd check it ASAP if you didn't fit it yourself.

Chris at Octarine Services

Ouch. For what it's worth, I bought a B three years ago and the oil pressure was not great from the onset. I am accustomed to 40 PSI at idle and 78 PSI at speed running 30W oil. These have been the readings since the car was new and the engine, which now has almost 300,000 miles on it, has been rebuilt twice.

For the B, the oil pressure is about 50 PSI at idle and 55 PSI at high revs. I changed the electric oil gauge for a mechanical one suspecting the sender but the reading is identical. I have put about 65,000 highway miles on the car during the last three years and the pressure has not dropped a bit. The engine does leak oil everywhere, it is the worst leaker of all the British cars I have ever owned. If your engine is in the car and running well otherwise, you might give it a chance to see if oil pressure drops with use. I assuming that you are running 20W-50?
Glenn Mallory

Herman-
Properly rebuilt, the oil pump should deliver 60 PSI to 70 PSI (4.22 kg./cm.2 to 4.92 kg./cm.2) at idling speed when the oil temperature is 2000 Fahrenheit (93.30 Celsius).

Take care that the oil pressure relief valve inside of the engine block operates freely. Its plunger (BMC Part # 12H 865, Moss Motors Part # 460-155) should have a satin finish chromium plating on it in order to prevent galling. Be aware that the interior of the plunger terminates in a truncated cone. A spacer (packing piece) (BMC Part # AEH 798, Moss Motors Part # 460-165) fits inside of the plunger and seats inside of this truncated cone, giving the oil pressure relief valve spring (BMC Part # 1H 756, Moss Motors Part # 329-210) a solid seat upon which to exert its thrust. If the spacer (packing piece) is not sandwiched between the spring and the conical surface inside of the plunger, then the base of the spring will not engage the plunger squarely, causing the spring to bow and consequently causing the plunger to tilt inside of the bore, thus causing it to bind. The oil pressure relief valve spring should have a free length (uncompressed length) of 3.0" (76.2mm) and a resistance of 15.5 Ft-lbs to 16.5 Ft-lbs (7.0 kg to 7.4 kg) when compressed to a fitted length of 25/32" (54. 8mm). In order to allow for fine adjustment of relief pressure, building up thickness of sealing washers will reduce tension of the spring of the oil pressure relief valve oil and thus slightly relieve pressure on the body of the relief valve if so desired. In a corresponding manner, installing shims behind the spring inside of the oil pressure relief valve will increase the tension of the spring of the oil pressure relief valve and thus result in an increase of the oil pressure. However, a less time-consuming method of adjusting the relief pressure is to install an adjustable oil pressure relief valve from Advance Performance Technology (APT Part # OPRV-ADJ). This clever, yet simple device permits the tension of the pressure relief spring to be adjusted to any desired level while the engine is running. Take care to lap the plunger of the oil pressure relief valve into its seat with a water-soluble 280-grit lapping compound in order to ensure idle pressure. Simply coat the beveled contact surface on the nose of the plunger of the oil pressure relief valve with marking fluid, and then lap it to its mating surface in the engine block until the mating surfaces display 100% contact. I use Dykem 80300 Steel Blue Layout Fluid in order to more easily distinguish the seat, but you can use a Sharpie black marker in order to accomplish much the same thing. Afterward, take care to flush out the lapping compound completely prior to reassembly.

Bearing down against the resistance of the spring of the oil pressure relief valve while trying to get the 1/2"-14 BSP (British Standard Pipe Parallel) thread of the domed spring cap (BMC Part # 12A 1851, Moss Motors Part # 460-870) engaged with its mate in the engine block is well-known to be one of the most frustrating tasks on the BMC B-Series engine. However, there is a way to make this somewhat onerous task easier. Simply refit the domed spring cap into the engine block without the spring, and then slowly unscrew it and mark both the spring cap and the engine block at the point where the threads disengage. This threaded domed spring cap is factory-sealed with two fiber washers (BMC Part # 6K 431, Moss Motors Part # 324-650), but one copper crush washer will usually work just as well, if not better, as it is less prone to oozing oil out onto the engine block. When re-installing the assembly into the engine block, align the marks, compress the spring, and then rotate the domed spring cap in order to engage the threads. Easy is good, hard is bad! Once you have the domed spring cap tightened down, torque it to 43 Ft-lbs (dry). Be sure that you have cleaned all of the threads first; otherwise, you will get a false torque reading.
Stephen Strange

Suggest changing the relief valve plunger with 9/16” ball bearing (may not fix your current issue which I suspect is a clearance or oil pump issue but will prevent other issues). Removes the chance of galling and sticking open. Lapping the plunger to the seat is overrated unless really badly eroded, not need with ball relief valve as has only line contact. (This modification is recommended by B series engine guru Peter Burgess).
Mike
Mike Ellsmore

I suspect the oil pump.

Years ago, I got one of those Made-(somewhere)-In-Asia
oil pumps. As a rule, I do not trust anything that is
made in that part of the world and so before installing it I took it apart and checked it.

The internals were grimy, and I found 2 small bits of
aluminum swarf in the intake tube. After a quick clean up I checked the rotor end float and it was right on at .006"(.152mm) - which is at the worst, far limit for what the factory deems as acceptable wear.

The factory recommendation says that the rotor end float should not exceed .005" (.127mm). The factory manual does not give a minimum end float number. Anything beyond .006" should be rejected.

I took some sheets of various grades of fine sandpaper
and laid them on a flat steel bench, and lapped the oil pump body until the rotor end float was around .001". Finished with #600 sandpaper.

I also lapped the oil pressure relief valve piston
by taping the piston on to the metal rod, and using
some abrasive household cleanser, lapped the piston
onto the valve face by hand - followed by a thorough
clean up. I used a high performance oil pressure
relief spring (Moss) and a small 1/16" spacer behind
the piston for added measure.

My oil pressure is at around 55-60psi all day long.





Daniel Wong

Daniel, I have always found Apple, Samsung and Toyota products made in Asia somewhere to be of superb quality.
Mike
Mike Ellsmore

The oil pressure relief valve also has line contact as the seat and valve angles differ.

Lapping is not the recommended procedure - insert a hard wooden dowel into a new valve, place it against the seat and give the dowel a good tap with a hammer to seat it.

The valve spends most of its time off the seat anyway as the oil pump produces more pressure than the blow off pressure of the valve - especially when the oil is cold.
Chris at Octarine Services

Mike, there's a big difference between electronic devices and engineered product. New pumps in my experience, both V8 and 1800, have needed considerable attention before I would put them anywhere near a re-build. Involving reaming crudely drilled, or even "as cast, oil ways, removing burrs, properly "mating" supposedly flat surfaces and setting tolerances.
Allan Reeling

I agree Allan, my comment related to the phrase “anything made in that part of the world”. I find you get the quality you pay for - MGA parts are still relatively cheap compared to other cars.
Mike
Mike Ellsmore

"I have always found Apple, Samsung and Toyota products made in Asia somewhere to be of superb quality."

They are made specifically for those named companies and to their quality control standards.

If anyone thinks every sweat-shop in Asia or anywhere else produces things under their own names for sale on eBay and makes them to the same standards they are very much mistaken.
paulh4

Hi all,
Problem solved. I replaced the(new) oil pressure relief valve and spring with the original one and added two washers(2,5mm) between the plunjer and the spring. I also replaced the oil pump with a new one (costly but noticeable better quality).
I now have 70 psi at 2000rpm and 40 psi at iddle with a warm engine. So I do not know wich of the two caused the problem but I still suspect the oil pump.
Me happy!!
Thanks for the advice.

Herman
H. Jorens

Did you take engine out to replace oil pump or just remove sump? Would be interested in internal photos of oil pump bits and clearance measurements for rotor and end plates. What was brand of replacement unit (County?).
Mike
Mike Ellsmore

Mike,
I replaced the pump with the engine in the car. Easy job.Some people say you have to lift the engine to reach the three front bolts but with an angled socket the bolts can be removed without lifting the engine. The sump comes off without a problem. Then you can undo the three nuts from the pump and you have the pump in your hands. When you refit the pump you have to turn the engine a bit to let the pump gear engage to the camshaft gear.
The first I used pump was a new one that came from a UK suplier. When I opened the box I tried to turn the pump by engaging a flat bladed screwdriver in the slot for the gear. The pump did not turned like one would expect. When I tried to open the pump to fill it with vaseline, I had difficulties to lift the lit from the pump. The clearance measurements for rotor and end plate where ok(see the manual).After the problems I had I bought a second new pump here in Belgium at Angloparts. They are more expensive but they sell the best parts they can find on the market.The pump came in a plastic bag with no name or country or so. The pump "felt" better to,she turned freely, opened like it should, the slot in the pump shaft was perfect.
Maybe I had bad luck with the first pump but I always be suspicious with new parts. I can not say that the low oil pressure I first had came from the oil pump or the oil pressure relief valve, because I replaced them both at the same time.
Sorry I do not have any photos from the internals but the workshop manual describes perfect how to meassure the clearances.

Herman
H. Jorens

Thanks Herman, now you have the first pump removed it would be interesting to open it up again, clean and see if there is any damage. Are clearances still within the workshop manual tolerances? Perhaps a couple of photos.
Regards
Mike
Mike Ellsmore

This thread was discussed between 21/12/2017 and 31/12/2017

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