If it sounds good with the 5-W-30, it will be even better with the 10-W-30.

If you ran the engine for less than an hour the oil never got really hot so 5W-30 or 10W-30 would make no difference. If the oil pressure gauge is accurate you have another problem. Perhaps too much SeaFoam got into the oil, the by-pass valve in the oil pump is stuck or a main bearing is burnt out or all the mains are very loose (doubt the last two).If in doubt about the 5W-30 add a quart of straight #40 and see what happens.
Last summer I ran all 5W-30 in my 1950. The oil pressure when hot was exactly the same as it is with 10W-30 except it didn't peg the needle when cold.

Thanks Ray & Gene. I'm going to test it again this afternoon and see what happens. Going to add a qt of #40. Opps. Forgot to add that I'm running it with a water hose into the water pump and out to a drain from the top. No radiator. Should be OK. not? It comes out not even luke warm.

If your running cold water thru it the oil is never getting up near normal operating temperature....forget the #40 and find the real cause of the low oil pressure. 5W-30 0r 10W-30 should give you at least 10 pounds of pressure at idle an 15 at higher engine speeds.

Thanks, will do. Planned on dropping the pan anyway.

Started the engine up, ran for awhile and drained the new oil out and it came out as black as an ace of spades and quite thin. Will leave it this way until I can drop the pan.
Now to get the spare '31 running.

Note that the last post was on 3-16-10.
Dropped the pan to see if I could find out why there was very little oil pressure. The bottom of the pan had a lot of heavy gook in it. The oil screen was close to 100% plugged and only a little hole in the screen for oil to get through. My initial thought was to get the oil pressure working and then close it up to save as a spare. Checked each rod and could move them back and forth by hand. Dropped the #2 rod and it looked in perfect shape as did the crankshaft. There were 2 shims on 1 side and 1 on the other. Dropped the 2nd main bearing and that also looked in good shape except for a very small piece of babbit missing no bigger than 2 stick pin heads on the bottom. Dropped #5 and same as #2. I changed my mind and will take the head off and grind valves and put in new rings as I think I will have a reliable motor when I get done. But first I'm going to go through the spare '31 now so I have a good spare for that one. Just one thought, if the bottom mains look good, can I expect the top to also be good without checking them?

Which engine is being described? The 1931, 1949 or the 1952?

Oh Oh. The '49. The '52 sounds great in the '49 and the present one in the '31 was put together just to get it on the road and sounds great at 35 mph but I want a spare just in case so I'll do my other '31 first.

Jerry
In most cases the lower main bearings and the upper conrod bearings do all the work so wear the most. If the crank is smooth there generally isnt much of a problem providing the babbit hasnt pounded out.
That piece of babbit missing is not a good sign but may have been a air bubble from manufacture.
Tony

Thanks Tony, I'm gonna cap it up and work on the '31 next week to have it ready for the summer in case the one in the car goes bad. Then work on the '49.