JET951

Hi Thom,
Like Laust has mentioned above, i am a little worried about that bolt in the last picture. of all the heads we have seen i have not seen that before. Could it be restricting the flow into the cam box? It does seem to extend out a lot
Here is a picture of a head we have laying around at work.
Sean

MG944

The oil supply hole should not have that bolt there. There should not even be anything tapped there. Cut the bolt so that it doesnt intrude into the supply hole and go from there.

Tom M'Guinn

I think Thom has a 2.7 head, and if so that bolt is normal if memory serves.

I'd triple check the oil passages in the cam tower -- spray brake cleaner in the oil holes and make sure it squirts out the oil holes for each of the lifters. I'd also back off on the oil weight -- 60W is pretty darn thick, not sure why you'd want to run that?

I trust these are stock camshafts, and that you don't have any dropped valve seats? Did you try putting a straight edge across the valves to make sure some aren't low?

JET951

Learn something new every day, i have not seen that bolt there, and seeing how rare 2.7's are around here i had never looked. Hey Tom from your memory does that bolt extend out quite that for into the oil passage?
Sean

zerMATT951

If my car had that bolt blocking +/- 25% of the volume going through the cam tower, I sure as heck would pull it out, cut off 1/4" or so, then put it back in unless there is a clear reason to leave it that long.

gtuma

I'm almost positive that bolt is your problem. I have a '89 Turbo head on the shelf, they use the same bolt set-up to retain the oil screw. It should look like the picture below, Notice how the bolt does not block the hole at all. It would appear someone did not use the correct retaining bolt, and as a result it is blocking a lot of your oil flow.

Tom M'Guinn

Here is a picture of mine. I can't tell from your picture Thom, but your bolt may indeed be longer than stock? Now, whether than would make any difference, I'm just not sure...(but when in doubt, stock is good)...

Thom

Folks, thanks for your input, much appreciated.

This type of OPRV is a cylinder in which a piston slides upwards as its being pushed by oil flow coming from the block. As I took it apart, I noticed that it was assembled this way, from the lowest to the highest point :
piston - short/soft spring - long/stiffer spring - "hat" with tapped hole

My understanding is the following :

- The soft spring forces the piston to seat down when there is no oil flow, resulting in keeping oil in the top end when the engine is not running.

- The longer, stiffer spring prevents the piston to slide too far upwards thus block the holes where oil enters the valve, which by then would prevent any oil to make its way into the cam housing. The piston, because of its H shape, contributes to regulating oil flow along with the stronger spring.

- The “hat” closes the assembly. The FWM states that the hole is tapped for allowing using a long bolt to pull the whole OPRV assembly out of the head.

In my case, as I had previously taken the OPRV apart, and in order to secure the hat in a blocked position, I chose to use a longer bolt so that this hat could never move upwards.

In any case, oil does not flow through the hat, and has no mean whatsoever to push against the bolt. Oil flows upwards into the cam housing alongside the two flat-sided faces of the OPRV, one facing the opposite side of the head, the other side facing the front end of the head, as shown on gtuma's and Tom's pictures above.

I hope the functional sketch below is clearer than my wording.

I checked for blockage in the holes of the cam housing, they are all clear.

What I think I can say now is :

1) if I lose 1.5 bar of oil pressure when the engine idles without the OPRV then there may be no blockage in the oil valley in the block going to the cam housing, and there is usually ~1.5 bar of oil pressure right before the inlet of the OPRV.

2) if lifters still tick when running without the OPRV, then either the oil is too thick for the lifters to get loaded and/or the lifters are (now well) out of order.

Laust, as I had the cam housing on the bench I laid the gasket on it and noticed that the hole for the oil supply was still larger than the oil valley in the cam housing.
This suggests to me that opening this hole to as large as the size of the OPRV might not get me better results?
Maybe the last run I did, without the OPRV, put the lifters on their last legs as oil necessarily has to go through them before it makes its way back down into the block?

As Tom stated it's a 2.7 head.
I put a straight edge above valve ends and they all measure about ~13.5 mm to the mating surface of the head to the cam housing. According to the FSM, this is fine. Do Ti valve retainers require a different setting?

Sean, in your S2 head, what kind of valve do you have? PET shows an OPRV of a similar design.
Interestingly, PET also shows that Porsche apparently returned to a ball+spring type regulator in the 968 head...

Thom

Is there an easy way to check for blockage in the oil gallery in the block?

reno808

UMMM i dunno if this makes a difference but there is a chuck of metal missing from the lower left hole

Tom M'Guinn

Thom -- just checking but you do have both locating pins in place right? If you need a loaner OPRV PM me...

Thom

Tom, yes both dowel pins are in place.
Having in mind the issue you went through with blowing headgaskets, I checked holes' depths and they are fine.

Thanks for the OPRV, much appreciated, but I'm pretty sure the used one I have on the engine now works as it should

Anyway, yesterday I reassembled the cam housing after reinstalling the good OPRV and cutting the gasket above the oil supply hole so that oil could not push the gasket upwards.

Here is a video after getting back home from a 40 min test drive.


One would certainly say it sounds as bad as on the previous video, but it actually doesn't sound as bad in reality, when standing in front of the engine.
I'm thinking that maybe lifters are more loaded with oil than they were before, but yes they still tick somehow when the engine idles...

Here is a pic showing how I cut the gasket.

reno808

Still sounds like a old Mercedes estate. it def sounds better. maybe the lifters are just bad now.

Tom M'Guinn

How frustrating this must be. Do you have a spare cam tower you could try?

Duke

I think Thom wrote he had tried a different cam tower earlier.
Next step would perhaps be to try a different head?