Questions for Lyc O-320 Gurus

[The Green Baron]

1: Does anyone know why the rods need to bolt on to the crankshaft with the numbers facing down towards the sump? They look like they're symmetrical so why would it make a difference?

2: I have a non adjustable type oil pressure relief valve. Does anyone have a good rule of thumb on how to adjust it with washers/spacers?

3: I just put on a one piece nose seal on the crankshaft (delivered the baby in reverse). Why is there a spring on the rear side of the seal? Seems like a pretty flimsy spring and would not do much.

Thanks in advance
John

[osxuser]

No idea on the rods.

Adjusting the pressure relief valve is simple, just add a AN960 or 960L if you need to bump the pressure up, and remove one if you need to bump it down. There is no set number for how much it will adjust for any given number of washers. If you have any real problems getting pressure, make sure the ball and the seat look in good shape, if so, the spring could be weak.

The nose seal. I'm not sure of the physics involved, but the nose seal doesn't work without the spring in it....

[N941WR]

Originally Posted by osxuser

...Adjusting the pressure relief valve is simple, just add a AN960 or 960L if you need to bump the pressure up, and remove one if you need to bump it down. There is no set number for how much it will adjust for any given number of washers. If you have any real problems getting pressure, make sure the ball and the seat look in good shape, if so, the spring could be weak....

This is correct but Lycoming limits the number of washers to something like 8.

I had to add three to my O-290-D2 to get the PSI up where it needed to be. This is really a trail and error deal. In my case, my oil pressure was too low at idle so once I had the baffles off, I simply added washers until it stopped dropping into the red at idle. Note, you need to do this on a hot engine.

You can also buy different strength springs, if you need. Sky Geek has them. They are colored based on how “strong” they are.

[Low Pass]

Originally Posted by The Green Baron

1: Does anyone know why the rods need to bolt on to the crankshaft with the numbers facing down towards the sump? They look like they're symmetrical so why would it make a difference?

2: I have a non adjustable type oil pressure relief valve. Does anyone have a good rule of thumb on how to adjust it with washers/spacers?

3: I just put on a one piece nose seal on the crankshaft (delivered the baby in reverse). Why is there a spring on the rear side of the seal? Seems like a pretty flimsy spring and would not do much.

Thanks in advance
John

1. Consistency of installation I guess. I have no idea.

2. Answered.

3. You need the spring and need it all oriented properly. It's orientation is necessary for proper sealing since the higher pressure area is in the case. That's just how lip seals work. The spring helps keep the sealing surface running on the shaft (not lifting due to variations in pressure across the seal or shaft runout).

Trust me - use the spring and install it as intended. I've been through 5-6 seals trying to get one to hold. Even tried a custom tandem seal. The one that finally held was a one-piece (non-split) seal with a shortened spring.

[rocketbob]

1. Best as I can remember, it has to do with the direction of the bearing tangs and how the bearings let oil thru. I know the book specifically states the direction and its an easy thing to miss, but I looked at the same thing myself and it didn't make much sense to me.

2. I figure out how many washers are necessary to start with based on the main bearing clearances. If the mains have .002" or so clearance, I know the oil pressure is going to be high and will start of with two or three washers. If its .005", then put four or five washers in. The max is eight washers. Or just start with four and go from there.

3. Yes it is a flimsy spring but I take a 1/4" or so out of the spring by cutting it off to make the seal a little tighter. Its mainly there to force the seal to wear evenly. Every type of of oil seal I know of is constructed similarly.

[The Green Baron]

Thanks to all for your responses and recommendations!

Bryan, can you elaborate on "oriented properly" Not sure I know what you mean. Isn't there only one way to put it in? Unless you mean putting the seal on backwards....i.e. spring out?

The oil pressure relief valve came back from the overhaul shop with no washers inside and I am not sure how many were in there. The original spring and ball seat very loosely into the seat and I am sure there wouldn't be enough pressure created. Maybe I will start with 4 an960 washers like suggested and adjust from there.

Thanks
John

Originally Posted by Low Pass

1. Consistency of installation I guess. I have no idea.

2. Answered.

3. You need the spring and need it all oriented properly. It's orientation is necessary for proper sealing since the higher pressure area is in the case. That's just how lip seals work. The spring helps keep the sealing surface running on the shaft (not lifting due to variations in pressure across the seal or shaft runout).

Trust me - use the spring and install it as intended. I've been through 5-6 seals trying to get one to hold. Even tried a custom tandem seal. The one that finally held was a one-piece (non-split) seal with a shortened spring.

[Low Pass]

Originally Posted by The Green Baron

Bryan, can you elaborate on "oriented properly" Not sure I know what you mean. Isn't there only one way to put it in? Unless you mean putting the seal on backwards....i.e. spring out?

Disregard. I misunderstood your post and thought you meant you'd installed the seal over the crank flange in a reverse orientation. The flat face of the seal need to face forward and the lip/spring be in the aft direction.