Relief, Oiling system in a type 4 Options

[worn]

If anyone has read my previous threads my two week vacation turned from driving to lying on the creeper under the new engine and transmission. Low oil pressure after warm up. I ordered a new Melling 30 mm pump and we shall see, but at the same time I looked into the pressure relief system - especially where it shunts oil away from the cooler because it is easier to see in the car.

What I found surprised me. First, looking at two different cases (72 1.7 and 76 2.0) I found that the piston seats on a shoulder in the bore that is at most a mm wide, and is not at all uniform in width across the piston face. OK, maybe it isn't supposed to seal.

Second I found that by the time you have opened the valve to shunt past the cooler, you are also dumping into the sump. That is there is a small overlap between the outlet to the oil gallery and the grooves cut in the bore leading to the sump exit.

Finally, the piston is simply loose in the bore. I can understand a fear of seizing, but there is no way that with my system oil isn't streaming into the sump, and it will stream faster as it thins - much faster.

I also spent a long time cruising the Samba - they ought to know whats up. What I found is a recurrent theme of new engines built in a variety of ways making low oil pressure. Many people were happy with what I ended up with - 10 psi at idle. On a new engine.

It is steel against untreated aluminum, so wear would be expected, but mine do not look worn - just poorly made. Maybe they are worn and I cannot tell. I got a face full of oil on one attempt at examination, so I may have missed things.

It seems an ideal situation for machining or sleeving during the rebuild, and I actually found a manufacturer of a sleeving kit with a ball bearing valve.

Thoughts ladies and gentlemen? (IMG:style_emoticons/default/idea.gif)

[yeahmag]

So you went from 10PSI to 20PSI at idle with all things being the same?

[worn]

So you went from 10PSI to 20PSI at idle with all things being the same?

No, I changed to a thinner oil too. I agree though, I expected more - that is why I went with the 30 weight to start up with. At this point when I change the oil I am going with a heavier oil from a reputable company and just drive it. It is a summer car. I think I won't see the oil light and will be able to enjoy the car. New bearings and excellent journals, but the case - well I am not sure. Bearings - well maybe they aren't right. I just don't know, but my mood has improved.

[r_towle]

So you went from 10PSI to 20PSI at idle with all things being the same?

No, I changed to a thinner oil too. I agree though, I expected more - that is why I went with the 30 weight to start up with. At this point when I change the oil I am going with a heavier oil from a reputable company and just drive it. It is a summer car. I think I won't see the oil light and will be able to enjoy the car. New bearings and excellent journals, but the case - well I am not sure. Bearings - well maybe they aren't right. I just don't know, but my mood has improved.

you got 10 psi from honing the relief bore?
Did you change the oil pump?

Rich

[worn]

So you went from 10PSI to 20PSI at idle with all things being the same?

No, I changed to a thinner oil too. I agree though, I expected more - that is why I went with the 30 weight to start up with. At this point when I change the oil I am going with a heavier oil from a reputable company and just drive it. It is a summer car. I think I won't see the oil light and will be able to enjoy the car. New bearings and excellent journals, but the case - well I am not sure. Bearings - well maybe they aren't right. I just don't know, but my mood has improved.

you got 10 psi from honing the relief bore?
Did you change the oil pump?

Rich

I got five to ten in the end. So I am at about 15 at idle. I can easily make the Porsche manual spec, which is stated for 70 degrees c. But I am at more than 110 degrees c. That still leaves me in the white with the new style gauge, or probably wher the beginning of red used to be. The pressure runs strong until about mid gauge. So the first twenty minutes are great. Btw cooling system works like new.

Now I am worried about cylinder head temps vdo under the spark plug. Going up hill, and hills are gentle here, at 65 brings me quickly to 400 plus. I went with 2056 and calculated 8.5 compression and am about ready to indefinitely jack stand my 914.