Dougs951S

I'm posting this here because I have a mystery part on my hands, and I believe it is actually an S4 part. I am reassembling my 16v head (going on a stroker 951) and have a question about 16v (32v for you v8 boys) chain tensioner oil supply tubes.



The lower J shaped tube is definitely the correct part for a 2.5 liter 944S head. The upper, S shaped tube is the unknown part. I know for certain it goes inside a 928S4 head, what I dont know is if it also has a purpose inside my 944S head (I doubt it, cant be two oil supply lines right?) and why porsche changed from the J tube to the S tube. I dont know what type of oil supply tube the 3.0 S2's use, but I thought the S4 cylinder heads were for all intents and purposes, identical to the 944S? Did I just accidentally get my hands on a part that does not go on a 944 at all?

Thanks

Dougs951S

It seems upon further inspection, the upper "s" shaped line was actually the correct one for my head. I am puzzled since I can not find this part in the 944S PET anywhere, they all show the "J" tube which doesnt seem to fit in my head....I'm confused.

Edit: My own ignorance is astounding. Is this a simple case of a superceded part and they both work just fine? It actually looks like they'll both bolt up and clear the cam, though I havnt tested this.





This shows how the S line is supposed to bolt up





And this shows how the J line bolts up

Is one better to use than the other, both are in very good condition?

FRporscheman

I've heard people like to reinforce the mounting arrangement of the tensioner, so that it can bolt to 2 spark plug wells rather than just one, like the 968. When extra material is welded to the other spark plug well and the tensioner to bring them closer to each other, depending on the shape, I guess one tube would probably no longer work.

Dougs951S

I wonder why porsche produced two different tubes, there must be a reason for the change? I cant find the S tube anywhere in the PET or anywhere online except in reference to GT/S4 heads. Is it maybe a 968 part?? To top the confusion salad off, the guy I got the S tube from claimed it came out of a stock 87 944S head, while my 16v head also off an 87 944S had the J shaped tube shown in the PET.

Vilhuer

J tube is for 944 tensioner and S is for 928. For some reason factory did two different versions of tensioner and thus had to also use two different style pipes. They could have made two different S or J but for some reason did different style pipes. It's possible to use 944 parts on 928 head and very likely also other way around but both tensioner and pipe need to be one or another style to work. They cannot be mixed as there is about 3-4mm difference in how long distance is from pipe feed hole to tensioner feed hole on each pair. 944 J pipe and 928 tensioner is 3-4mm too short or long to fit oil feed hole in both 928 and 944 head while 928 S pipe and 944 tensioner is 3-4mm too long or short to match oil feed hole in both 944 and 928 head.

docmirror

I'm going to go with an engineering answer, but I may be way off.

Mandrel bending a U shape in a thin wall SS tube can lead to greater stress riser, and potential for leaks from vibration cracks. The general rule for tube bending is least bends, greatest radius that can be accommodated. In this case, I'm wondering if the S tube superseded the J tube, or vice versa?

I'm sure either will work, it's just a matter if Hans was looking at one on the drawing one day, and said 'I can improve this!', thus the alternate part was born.

That's my story, and I'm sticking to it. YMMV, don't try this at home, pro driver closed course, objects in mirror, and may cause **** leakage.

Dougs951S

Thanks, I appreciate the insight. it appears I have a 928 tensioner in my 944 head since the s tube is the one that bolts up. it clears the exhaust cam so I'm going to run it. I appreciate the help.

Dougs951S

In the interest of posterity, I did an experiment and documented the results.

It turns out both tubes work on both tensioners (I assume), I double checked the part number and I have a 944 tensioner. The J tube bolts on as expected, and the S tube bolts on well in multiple positions (one is flipped over).








Sorry for the blurry images, it was hard to take a picture one handed. I have to agree with docmirror, it was my first thought that it was simply a superceded part and I agree that the S tube is probably the superior design. Any thoughts anyone?

Vilhuer

I have tried both tubes and tensioners on 928 head. They only worked together with each other, not mixed. Difference was far too large to be just manufacturing tolerance. Once both banjo bolts were in tube it was clear there is something wrong and it will not fit without hammer. Both correct combinations fit right in, both of them on same exact head.

Dougs951S

They bolted up fine?? I'll go double check to make sure I'm not crazy.

Vilhuer

J and 944 tensioner is in one 928 engine as I type. Bolted right in. Drove it earlier today for example.

Dougs951S

They both fit on my tensioner.

Vilhuer

Which is very interesting. There might be more part styles around than just 2 + 2.

V2Rocket

Bumping this up...it might be that the oil feed hole drilled into the head wasn't always in the same spot.
The tube is small enough it could be tweaked as needed for assembly.

I noticed yesterday while trying to put a 944S chain tensioner into a 928S3 head, that the "S" tube was 2-3mm or so too long...but with a little tweaking (heating and bending a little more, maybe) could be made to work and clear the cam.

The 944S "J" tube I have doesn't seem like it would work in the 928 head.

What makes this all more confusing is...the 944S head I am working on, is the very same head that Dougs951S posted in the beginning of this thread

M. Requin

In the interests of posterity, it would be really really great if you could upload those images to the Rennlist server, so they will still be there for, actually, posterity. You may not have browsed RL enough yet to see how many pics uploaded to fotophucket et al have been lost to that very posterity. Your info is good, and out to be properly archived.