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MG MGB Technical - Engine oil capacity 3-Main MGB

I am wondering if the oil dip stick in my 3-main MGB engine is correct. According to Haynes Repair Manual,
the oil capacity for this engine is:

Sump: 9 US-Pints
Oil Filter: 1.2 US-Pints
Total 10.2 US-Pints or 5.1 US-Quarts

When I change the oil, I find that it takes only 4.25 US-quarts to reach the Max line on the dip stick. I am not using the original oil filter as I have switch over to the more modern spin-on filter. The capacity of this filter is .667 pints. Adjusting for this difference 9+1.2-(1.2-.667)=9.667 US-Pints or 4.834 US-Quarts.

As said earlier, it takes only 4.25 quarts to fill to the max line. I am still 4.834-4.25=.584 US-Quarts, or more than 1/2 Quart, short according to Haynes. Is there an explanation for this?

I am hoping that someone would be so kind and measure their dip stick and compare their measurements to mine.

From Tip to Min Line: 1-23/32(43.5mm)
From Tip to Max Line: 2-3/32 (53mm)

Thanks in advance,
Frank Grimaldi
Frank Grimaldi

Hi Frank,

Just looked at mine, I have a 1964 18GA 3 BRG, and my min and max marks are the same as yours, so it looks like your dipstick is probably correct for your car.

If you don't have the original filter, then it may be that your oil cooler isn't draining when you change the filter? When I change mine, the oil cooler to filter adaptor comes off too and the cooler oil drains out, or at least some of it does. Would that account for your missing volume?

Mike
Mike Winter

When you change the oil and filter some oil will inevitably remain in the engine. The factory oil and filter capacity listings are for an engine that has just been assembled and is still dry. RAY
rjm RAY

Mike,
My engine is not fitted with an oil cooler because it is installed in an MGTD. Unfortunatly, no room for a oil cooler.
Frank Grimaldi

I think it unlikely the cooler drains as the inflow/outflow hoses mount to the top surface. You might expect to drain some oil from the outflow hose if you can get it angled to do so.
Regards
Roger
Roger T

The dip stick is supposed to hit a small raised lump in the bottom of the sump and the dip stick may be going past it which it can do if pushed hard down or has a slight bend in it.
Garth
Garth Bagnall

Tip to line is irrelevant, as the tip can be anywhere off the bottom, I was under the impression the rubber seal at the top of the stick rested in the tube opening, the stick didn't rest on the sump. If that were the case crankcase breathing would be pulling dirty air into the sump through the inevitable gap between stick and tube, on positive breathing engines anyway. It needs to be from the top of the tube down to the lines, if you are comparing stick to stick. Strictly you then also need top of tube to bottom of sump, but even that depends on the relative flatness sump base to sump base.
Paul Hunt 2010

I appreciate all of the comments.

Re: Garth Bagnall: My sump does not have a raised hump.

Re: Paul Hunt: My dip stick does not have the original seal or any type of stop. The dipstick rests on the bottom of the sump pan.

Does this fix make sense?
Assuming that the Haynes Repair Manual is correct and the required amount of oil for a full sump is 5.1 US-Quarts then...

1. Adjusting for the difference in the oil capacity between the original oil filter and the spin-on that is installed, pour 5.1 quarts(less the difference) into the sump.
2. Run the engine to ensure that oil has been properly circulated and, allow the engine to rest a half an hour or so to allow the oil to drain back into the sump.
3. Insert the dipstick into the tube and adjust the depth so that the actual oil level and the Max line on the dipstick are aligned. Note the depth and place a permanent stop on the dipstick.
4. Fit an old distributor end spark plug wire rubber cap on the dipstick to create a seal/cover between the dipstick and the tube.

What do you think???
Frank Grimaldi

Looking at the Parts Catalogue drawings (not always guaranteed to be accurate) whilst the 3-bearing stick seems to have and the 18GG on engine stick definitely has a stop, the 18GB to GF are shown without i.e. a plain stick. However these intermediate engines have a 'dust cover' shown separate to the tube and stick, which looks very similar to what is shown on the 3-bearing stick. That would seal, but the stick would still rest on the bottom of the pan. If there wasn't a pad of some kind here then the stick could well eventually wear through the pan unless the dust cover was tight enough to stop the stick rattling around. The cover is very like the straight ones on an HT lead on the distributor cap. Capacity is always going to be tricky, short of test-filling and running a dry engine only several examples of what other people use to get up to the Max is going to be a guide.

Paul Hunt 2010

Sumps commonly get bent, especially if the engine has ever been out of the car, and it's always upward = less capacity. You can calculate how much depth a half quart is, I won't waste my time. You could also calculate temp coefficients of expansion, barometric pressure, etc etc. For B series engines, Change the oil and filter, put 5 qts in - that's the level. Been doing it for 45 years, sometimes 10 cars a day.
Lots of early cars have the stick resting on the sump bottom. Others have a stop brazed on the stick, with felt or rubber seals. I can't recall exactly which cars have what, and it doesn't matter. The stick should have a bend in one leg that causes it to be snug in the tube, so it does not rattle about. Single leg sticks can be bent (slightly) similarly. Some sort of dust seal should always be contrived, and the HT boots are usually good for this.
Worrying about .1 or even .5qt is silly, and quoting thousandths of a qt is ludicrous. If you were a qt or more off, I'd worry about restriction of the pump pickup due to the sump bottom being smashed upwards.
If you still want to worry, post a pic of the bottom of your sump and one of us will no doubt have an opinion re how badly it's bent!

FRM
Fletcher R Millmore

I agree with Fletcher. I always just use 5 quarts. I know some people are worried about running with too much oil, but my B burns some oil anyway.

I have the Moss spin-on filter conversion and use a NAPA Gold oil filter that is equivalent to the Fram PH3600. There was a LBCarCo tip a few years back that said you could also use the Fram PH3614 which is 3.34 inches tall instead of 4.92 inches. I kept the email but have not tried this alternate/smaller filter.

I have an oil cooler, but as was said, the oil doesn't drain out of the cooler when you change the engine oil.

The dipstick on my 18GA bottoms out when pushed in. There was no dust cover, although I did purchase one 15 years ago from Moss. Wish I would have thought about just using an old spark plug wire boot.
Bill Barge

This thread was discussed between 24/04/2010 and 28/04/2010

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