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The 100 Forum

oil pressure

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gramos Avatar
gramos Graham Foster
Kefalonia, Greece   GRC
OK , today the new relief valve spring was replaced with a " softer " value spring and the backed down to 60 lbs at a fast idle and 80 lbs at 2000 + rpm
the sump was dropped to check the infamous oilway beneath the relief valve was clear , which it was .

As we live in a Healey- remote place I made a new sump gasket , instead of ordering one ,
this was , however , made from standard gasket paper which is substantially thinner than thee original gasket .
Because of this discrepancy the gap beneath the relief valve drain back hole is minimised , thereby restricting the by passed oil from clear access
to drain back down to the sump .
This restriction is known to have the effect of raising the oil pressure ,
(I hope this is easy enough to follow?)
Tomorrow Iwill grind further access into the aluminium sump to allow good drainage and bolt it all up .
After decades of working on these and other engines it is refreshing to discover new solutions !

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Wilbert Avatar
Wilbert Wilbert Peters
Smilde, Netherlands   NLD
1954 Austin-Healey 100 "Cobra Nose"
1955 Austin-Healey 100
This is indeed the problem. The supplier mentioned to modify the oil sump and the return pipe. But he don't mention that when you use the sump without the original cork gasket that you have to modified the aluminium sump by making a little space for the relief (like in the original gasket).
He also don't mentioned that you should shorten the oil dipstick a 3/8 inch (about 9 mm) otherwise you put to much oil in the block (the stick is resting on the bottom of the sump and this bottom is 3/8 inch higher than the original)

gramos Avatar
gramos Graham Foster
Kefalonia, Greece   GRC
Hi Guys , Here is an up date on the oil pressure issue I have been experiencing .

I removed the aluminium sump , and whilst in the area dropped out the oil pump for good measure as it had been working overtime !
The oil pump was absolutely fine , no worries there .

I then made another sump gasket from 2mm thick gasket paper and fitted it to the sump with gasket sealer , so this is in addition the the existing 1mm gasket which is sealed onto the block .

I then radiused the oil bypass to sump hole to allow easier run off ,and ground away the part of the sump adjacent to the hole , again to allow better flow .
I bolted it all back together , this morning , then bled the air from the oil pressure gauge pipe and .....

60 lbs oil pressure at 1000 rpm !

To conclude then ,
the ali sump needs fettling and the gasket must be 3 mm thick ,
this ensures the oil will drop back down to the sump after the relief valve has opened and oil pressure readings will be normal ,
not 130 + as in this case .

Wilbert , it was an interesting idea to alter the dipstick to regain the level of the original steel sump ,
however ,
the ali sump is longer than the standard type , so the level must remain the same on the dipstick
I filled the filter and the sump with 7.5 litres and it was just above MAX .

(7.3l as stated in the manuall )

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Wilbert Avatar
Wilbert Wilbert Peters
Smilde, Netherlands   NLD
1954 Austin-Healey 100 "Cobra Nose"
1955 Austin-Healey 100
Hi Graham, It's not really the capacity that I mentioned (liters) but when you not alter the dipstick, the level is to high with the result that the crankshaft is in the oil.
I think when you fil with the original length of the dipstick, the oil is above the top of the all sump.
Regards Wilbert

gramos Avatar
gramos Graham Foster
Kefalonia, Greece   GRC
I have checked the volume of each sump and the aluminium sump has a smaller capacity even though it is longer , by about 8% , so Wilbert is right in saying the dipstick reading is incorrect when using the aluminium sump .So I have measured the level difference and have a simple solution which involves no alterations , when reading the oil level with aluminium sumps use the MIN mark as the MAX .

Wilbert Avatar
Wilbert Wilbert Peters
Smilde, Netherlands   NLD
1954 Austin-Healey 100 "Cobra Nose"
1955 Austin-Healey 100
Don’t forget to mention in your book for a possible next owner

Michael Oritt Avatar
LUSBY, MD, USA   USA
In reply to # 207536 by gramos I have checked the volume of each sump and the aluminium sump has a smaller capacity even though it is longer , by about 8% , so Wilbert is right in saying the dipstick reading is incorrect when using the aluminium sump .So I have measured the level difference and have a simple solution which involves no alterations , when reading the oil level with aluminium sumps use the MIN mark as the MAX .

Graham--

Working from memory I believe that an oil and filter change on my 100 with stock pan takes about 6-7 quarts US, and the difference between the low and high marks on the dipstick is about one quart US, or approximately 15% of the oil by volume. If your measurement of an 8% difference in pan capacities is correct AND if the AL sumps sides are vertical then theoretically your new full mark should be about midway between the present ones. That said, I would assume nothing and establish new marks by direct observation of oil level while adding oil quart by quart.

BTW I have drilled small holes, perhaps 1/16" in diameter at the "add" and "full" as it is much easier to read the oil level by observing whether or not the hole(s) are filled by an oil film rather than observing oil line on the dipstick, especially when oil is relatively fresh and not dark from particulates, etc.



Best--Michael Oritt
1954 Austin-Healey 100 (street)
1958 Elva Courier (track) FOR SALE
1959 Elva MK IV sports racer (track)
1961 Ginetta G4 (track)



Edited 1 time(s). Last edit at 2018-12-16 06:28 AM by Michael Oritt.

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