Oil - How Much and what weight? / Low compression on #3

[Felipe]

I just bought a 45MB, fairly original.
Engine compression is 1-90, 2-80, 3-60, 4-90#.
I'm hoping it is just carbon on the valves and will try cleaning with SeaFoam first.
I could not even find the # of Quarts it takes to change the oil?

I'm and amateur and any suggestions about trouble shooting low compression is welcome. Also, how many dern quarts does this motor take?!
Thanks!
pd

[XSNIPER]

4 in the crankcase and one in the filter, usually 30 weight.

[bmorgil]

Looks like this post slipped by. Good catch XSNIPER, I wonder if Felipe gave up on us?

[Felipe]

Thanks for the reply, I saw it and it was helpful. There is a follow up question now. When you drain the oil does the oil filter housing drain all the way? Mine only went down 1".

[bmorgil]

It drains slowly into the timing cover via the lower hose on the canister. It should drain all the way down and leave a nice mess of oil in the bottom. There is a small orifice that controls the oil return. Usually there is a few ounces left in the can that needs to be "mopped out" with a rag or two or three. If it isn't draining, use a veterinary syringe or similar device to suck the oil out, and pull the lower hose to check for blockage.