Erratic oil pressure

[Rowroy]

[Hophead]

Yep, starvation... had the same kind of issues with a 1776 about twenty years ago.... too big of an oil pump and no sump. I would throw a 1.5 quart sump on it first and see if that helps before i just tore into it. Perhaps the oil plunger work could be done easily as well. but I would not pull it without trying that first.... Depending on location the sensors can be wrong or off or slow to respond.

What does the oil look like? I would dump it, pull the plate and take a look for sparklies.Cut open the oil filter and look at the pleats. If all is clean then the bearings are probably not bad.

I wouldn't waste my time trying to chase down a pressure problem before I knew I had a consistant supply.
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70' Beetle Pan off Resto
2110cc
82 X 90.5
P&P 043 40x35.5
9.6-1 comp
FK-8
48 IDA

[Jimmy111]

Still. Starvation does not address continous low oil pressure. I have had many 2180- 2332's without deep sumps and yes on very hard cornering the oil pressure would dip But most motors lasted around 80,000 miles before starting to show low oil indications.
I had a Baja that was rolled, mashed, crashed, sunk and filled with water, overheated, broke oil cooler lines and generally bashed around at any oppertunity ( i mellowed out since then) and it still lasted 40,000 miles before oil pressure problems. So problems at 6500 miles??

[miniman82]

[koolkarmakombi]

Im with starvation.

Had the same symptoms on a nice new motor in a Kombi.

Long corners and throttle = red light on.

Topped up oil to very full and didn't do it.

Fixed with a deep sump and slower cornering.

[bugninva]

Jimmy, i'm with ya here.... if it were mine, it would be in for a tear down just to see...but i don't drive my ACVW's very often so taking one out of service is no big deal...
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[Jimmy111]

If he had a 21mm or even a 26mm pump I would agree with you.
But his pump is pumping 1/3 more oil then necessary to maintain the 10psi per 1000 RPM. Contrary to popular belief the oil control valve is OPEN all the time the motor is running until oil pressures drop due to wear. The oil control valve is there to maintain a MINIMUM oil pressure. Even when the oil control piston is open 100% of the time he should be able to keep his pressure high. Im sure he has not modified the relief hole for the piston to increase capacity. it is only 4 mm in diameter and can only handle the volumn of the 26mm pump. so by adding a 30mm pump you will always get a corresponding increase in pressure.
He only has 6500 miles on it. It is possible however unlikely that the bearings are That worn out already.

[Rowroy]

[74 Thing]

Starvation through acceleration and cornering means you need to add a sump.

If you need to machine your pressure control and pressure relief valve bores you can rent the tool from aircooled.net - at least they used to.

Good pressure is 10lbs for each 1k rpms

[bugninva]

i don't see a huge problem with his hot pressures...he's running 10w30 which will flow quite nicely when hot, and that means it can be being bled off at the control piston, or he may have some loose tollerances...the 42psi magic number on the stock spring is assuming the spring isn't softer than normal from years of use... if the oil starvation happened at higher rpm's there always a chance bearings were damaged and this could cause lower pressure...I still say the reason was starvation, not to say that that didn't cause other problems..
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[Jimmy111]

Yes but that does not explain the low oil pressure on the straights and at standstill
Where is the oil then?
Should be in the case. So the 38psi indicates another problem.

[bugninva]

[miniman82]

[bugninva]

[Jimmy111]

The 30mm pump does pump more than the valve can regulate properly. But that just resulte in excessive pressures. Happens all the time. The 42 PSI is if everything is stock. People change springs, pistons, machine the piston seats and other Bright ideas and it all effects the pressure that the valve will open and close at. The 30mm pump pumps a LOT of oil. It is backed by a 40-200hp motor so pressure is not a problem. If the pressure isnt vented somewhere something will break. Usually the hoses or filter or oilcooler but cases crack too.

The whole Idea of the pressure control valve is to lenghten the service life of the motor by being able to supply more oil as the motor wears out. as the motor wears more oil will flow around the bearings and less oil will flow thru the controll valve untill no more oil flows thur the control valve and the oil pressure starts to drop.
The control valve is not a pressure regulator but more of a waste gate.

[Rowroy]

Okay, I just went back and read Tom Wilson's write up on the pressure control and pressure relief valves and it got me thinking . . . .

According to him, the oil pressure control valve is supposed to open @ 42 psi. That leads to another set of questions:

1. Should a 30 mm pump be able to pump more than the pressure control valve is capable of flowing? If not, then I would think that the oil pressure would never get above 42 psi.

2. Are the "in and out" pump covers restrictive enough to limit enough oil flow that it could never generate more than 42 psi even with a 30 mm pump?
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Suicide is man's way of telling God, "You can't fire me; I quit!" - Bill Maher

[Rowroy]

[miniman82]

[Jimmy111]

The valve nearest the flywheel. The other valve is just a oil cooler bypass. But the piston should fit well in there too and not leak.

[Rowroy]