If you look at the engineering of the tensioner it is designed to minimize chordal action. A tradeoff is that the loading of the tooth is not parallel to a tangent of the pitch circle. This makes the tooth more vulnerable to shock loading which could occur in an aerated hydraulic valve train with a non-aerated design spec.

 

pretty funny. i found 2 teeth the first time stuck to the magnet on the drain plug., one on each side. then a couple of more then 1 more, but found 2more missing that didnt show up on the oil drain plug magnet. 7 years later, we took the engine out and the parts were still floating around (found both missing teeth in the block). all teeth accounted for!
I only changed the cam when I found two adjacent teeth missing on a cam. turns out, two cams had 2 teeth missing next to each other, but all cams had at least one tooth missing.

 

holy sheeit!!! I guess those pieces floating around didn't hurt too much then , huh?

I would have guessed they would have caused more trouble but guess not.

 

Sorry, for bringing this back from few pages ago, but I feel like these suggestions are pretty important while they didn't get enough feedback.

I'm pretty sure that someone had already suggested this (maybe even tested to some extent?), but here it goes anyways:
If you introduce fresh air to the cam covers via one-way valves, then vent the block through central outlet (modded oil filler) into some separator (pro-vent?) - it should:
a) Help counter the problem with oil drainback having to fight blowby gases - now fresh air will actually "help" oil drain back.
b) Introduce fresh air into crankcase, reduce crankcase pressure?
c) Remove oil ingestion into intake.

While this is pure speculation and "sofa engineering" - if this works like I imagine, it should be enough for stock engines used for some spirited driving on the street - or at least make them less likely to blow up.

Comments?

PS. One of the possible problems might be that engine will not pull enough crankcase vacuum "naturally" when needed, so the "fresh air" part will not work then.

 

Using stock air pump, just divert it to heads? I think fresh air alone without any help to push it in will not help much as crankcase is pressurised.

 

Hi Alex,

Yes, I suggested using a pump to do this probably five years ago. It was up on my site for a long time. It is a common technique.


Alex, my comment was actually meant as a compliment to you.

I suggest that I am not just a random forum guy. I solved the 2/6 issue five-to-six years ago for wetsumps up to a very high level of performance. I was asked by members of this forum to address the issue at that time. My, how time passes and memory fades. That is also partially my fault, however. I got really ticked off one day after I was told to please stay away because my remarks on comparative engineering with non-Porsche-928 items were not appreciated so I went through and deleted over 300 posts lest they taint other impressionable minds.

If people want to buy the product, they will. I think it is abundantly clear that I generally speak my mind and numerous times have acknowledged general character flaws.

 

That's an interesting idea.
By the way, if you don't mind me asking: are there any conditions (aside of idle) when crankcase could have pressure lower than atmospheric?
Rephrasing, when engine can pull crankcase vacuum?

I'm just learning how engine ventilation works, and would really like to clarify some nuances.

 

Louie has a really good piece posted on his site.

http://www.performance928.com/cgi-bi...ss_parent=1128

 

Ouch, now I feel myself quite silly.
Sorry about that, - sometimes it's hard to understand the original meaning when you don't speak the language daily. Please apologize me for jumping on you, I indeed got that sentence wrong.

On the "topic" note: please continue enlightening us about all the issues with these engines, it's really interesting to learn all this stuff, especially when a few knowledgeable guys start discussing something spiritually.

 

I met some of the most brilliant minds in the world in Moscow. One was later assasinated for it. Very sad.

 

Guess that happened in nineties, wasn't really the best time back then.

 

I was at least one who did this. I have all 4 cam ports vented one way (in only) from the airbox bottom. All breathing is now out the crank filler port via a 1" provent line. Provent output is plumbed back to the stock throttle body feed - but unidirectional (vac only - non-reversible). There is also a T to a second check valve to blow off the provent output whenever there is more total blowby than the intake can handle.

This does provide part time fresh air flushing of the crankcase & heads - however absent a RPM related pump the only thing sucking on the Provent output port is the intake vacuum...

At close to WOT there isn't at much intake vacuum so at the time of max blowby there will be no fresh air flow down the drains. However simply eliminating the contra-flow up to the head breather port is still a big plus.

So

a) Is true but due mainly to swapping the venting location - not fresh air
b) Fresh air flushing is good, but bigger venting is what reduces pressure
c) I seperate the oil through baffles, a scrubber stack & Provent to keep it out of the intake (assumes creating fresh air flow via intake suction vs an atmospheric/exhaust vented pump set up).

Alan

 

I may. I'm not sure what the exact connector is that you are looking for, but I may have it from my burned harness. The interior portion of the harness was unharmed so it seems likely that I have one somewhere.

 

Mark needs the '87 12 pin diagnostic connector and enough of the wiring to splice to his cut harness. Here's the pinout (from the WSM diagrams) to aid in identification. (NOTE: I haven't reality tested these, so they may not represent reality...) :


For the hell of it, here's what I get for the 89+ 19 pin connector as well- looks like the configuration is unique in 1989 and then is consistent from 90-94.

 

Mark:

I can help wire in a Sharktuner. I know how to hook it up even if your diagnostic connector is MIA.