R&R Engine, Cams, and Heads

[logray]

It's been a month long journey into the depths of my 1999 996 C2 M96-01, but I am finally there and the car is on the road again!

If you want to skip all of the boring commentary and head straight for the annotated pictures, then here is the link:

https://picasaweb.go...6pcarnut/Engine

(the email address associated with this account is not monitored, PM me or post here if you would like to send me a message)

Some commentary about the process for the readers.

PROBLEMS

1.) In the past 5,000 miles, oil consumption had gone from about 1 quart per 1500-2000 miles to 1 quart per 1000 miles. Still within Porsche spec, but such a rapid increase was worrying. I also knew that there were a ton of leaks that needed to be addressed, such as the spark tubes, camshaft covers, cam solenoid cover, AOS tubes, oil filler neck, and on and on and on. However leaks aside, the big indicator here that something was afoot was that bank 1's tailpipe was accumulating soot and producing purplish smoke on startup and high RPMs much more so than bank 2's pipe which was not exhibiting these issues.

2.) The oil pressure was fine at start-up, 5 bars. However when the car was warm it would fluctuate very slightly a few points in either direction of 1 bar at idle. Sometimes .8 bars. Cleaning the sender terminals did not help. I did not drive the car very long with this condition. In fact, barely at all before I decided to do this work. You don't want to mess with low oil pressure. This problem and the next one were what really got the ball rolling on this endeavor.

3.) There was an increasingly worsening knocking from bank 1 (1-3). The knocking would "seem" to stop after about 30 seconds on cold start, and I thought that this could be lifters or tensioners taking their sweet time to fill up with oil. One time the ticking lasted for 5 minutes. That really put the icing on the cake for the decision. After much Internet research, I determined that it could be stuck or collapsed lifter noise, because I couldn't tell whether it was coming from the top or bottom and that it would seem to go away after the car had oil filling the parts (but it was actually still there). In the back of my mind I also had thought that it could be oil pressure, blockage, valve guide, still could be worn rings, or perhaps issue with a chain tensioner or variocam unit as well. (after researching more and using the screwdriver stethoscope trick, I discovered that the knocking was present in cylinder #2, in the bottom end, but it was also present in #1). The exhaust valves in cylinder #2 were most heavily coated in carbon as well. Eventually, this realization and discovery later that the lifters were OK from my non-professional mechanical knowledge prompted me to pull the heads and have a valve job performed by professionals.

ACTION

Each problem individually above one might address on the surface by changing or swapping spark plugs, coil packs, and oil viscosity (which I had all done), however when those didn't have a noticeable affect on the issues, I decided to do something about the nervousness and drop the engine.

A bevvy of parts were ordered. Because a lot of the parts on this car is relatively inexpensive, I decided to R&R many of the components which I had isolated before removing the engine. For example the 4th and 5th chains cost only half that of the bicycle chains I go through several times a year on my road bike. Each of the three chain tensioners were less than $100. Some people might question why I replaced both oil scavenge pumps after only 75,000 miles and 12 years of life, however in the overall cost of the project the investment was minor. I'm glad I did too, because one was not rotating as freely as the other, and no where near as freely as a new unit. An LN engineering billet hex oil pump driver and genuine oil pump spring and piston were also sourced.

Waiting for the parts was actually the most discouraging part of the entire process for me. A few times I had to wait for parts from Germany which meant 7+ days. I replaced nearly every gasket, o-ring, and washer I could which was external to the engine, including some which are internal such as the valve seals (done by the machine shop) and head gaskets (can't avoid doing that or the bolts if you remove the heads). In hindsight I should have ordered the ARP studs for just a few hundred dollars more than the stock single use head bolts. I ordered 24 new "BMW" INA lifters, in case they were some of the source of the problem. Also in hindsight, instead of ordering individual gaskets and orings I could have ordered the complete gasket set, which probably had more in it than I was going to use but would have been easier (although somewhat more expensive) than ordering ala carte.

WORK

Here are the major highlights on what I replaced or work performed.

Complete valve job was performed by Riebes machine shop including: Cleaning, gentle bead blast, and light resurfacing, vaccum and pressure test. Three way valve cut, 5 new valve guides (2 were horrifically worn - the source of the knock), new valve seals, and overall inspection for valve train components (springs, etc.).

The machine shop also resurfaced my fabspeed stainless bank 1 exhaust header, it was badly bowed out in the center which plagued me with constant re-torquing, stripped threads, damaged bolts, and a lot of helicoils later. GOOD BYE exhaust leaks!!!!

Head gaskets

Head bolts

Variocam ramps (two were heavily pitted and scored)

4th and 5th timing chains

24 new (old style) lifters

LN engineering billet oil pump hex driver

OEM oil pump pressure spring & piston

Both oil scavenge pumps

Oil pressure sender (cleaning the terminals did not help)

All three external chain tensioners (all were scored)

Replaced many coolant and AOS hoses

New air oil separator

Countless gaskets, o-rings, & washers

Micro encapsulated rear case bolts

Replaced water pump (oem, peace of mind)

Replaced thermostat (oem, old one was lazy)

Resealed and inspected oil pan

4 new lambda sensors (3 were very "slow") - killer deal from Amazon

6 new spark plugs (packs have about 20k on them)

Fuel injectors sent out for test, cleaning, orings, and new filters

Oil filler tube and cap

New "04" coolant cap

10 quarts Castrol 5w40

Oil filter

Cleaned IACV

Thorough cleaning of engine exterior

Cleaning of any interior or exterior part I reinstalled

Thorough Intake plenum cleaning

Inspected DMF and clutch

Replaced about 1 quart of CHF P/S fluid

Inspected polyrib belt

New SAI check valve, hoses, tubing and elbows, and cleaning

Repainted coolant tubes

Flushed 12 year old Porsche coolant out and replaced all coolant with Peak Global using Uview Airlift 550000000000

Cam caps

Ordered new RMS but didn't install because old was bone dry

!!!!!!RESULTS!!!!!

The results of all of the above are restored confidence in driving the car. The oil leaks appear to have vanished, since the engine is so clean it is easy to spot fresh oil. Low end torque seems to have dramatically improved on the few drives I've taken. Although I've taken it there a couple times, I haven't yet "fully tested" the high end RPM range because I'm going to give it a bit of a break in and "get comfortable with the rebuild" period first. Oil pressure now stays dead straight on at 1.2 bars hot idle and 5 bars cold idle. Last and certainly not least, NO MORE smoke at startup or high RPMs (thank you valve job). Time will tell if the soot or oil consumption returns. NO MORE ticking or knocking (outside of normal lifter and valve train noise I hear on any car). Thanks to the new thermostat the car gets to temperature much more punctually than it used to. The engine idles much more smoothly than before, it stays pretty dead level on 680 rpm - whereas before I'm sure there were some leaks in the system it would fluctuate some, the plugs were fouled too so not surprised. Warm idle numbers are pretty much dead on with the factory DME set points.

Load signal 1.6 ms

Air mass 20 kg/h

Mat film MAF 1.35

Ignition timing 4.5 to 7.5

Spec air mass 17 gh/hr

Spec air adapt 1 kg/hr

Injection time 3 ms

Oil temperature 207.5F (stage 1 is on, idling on a hot day in my garage)

Oxygen sensing 1-3 1.04 avg

Oxygen sensing 4-6 1.03 avg

Range2 Cyl 1-3 FRA .98

Range2 Cyl 4-6 FRA2 .98

Range1 Cyl 1-3 TRA -0.14

Range1 Cyl 4-6 TRA2 -0.14

02 ahead cat bank 1 fluctuating .09 to .77

02 ahead cat bank 2 fluctuating .09 to .77

02 behind cat bank 1 fluctuating .09 to .71

02 behind cat bank 2 fluctuating .09 to .71

Cam 1 deviation 3 degrees

Cam 2 deviation 3 degrees (was 0 before I did the work)

Rough Running Thresh 10.5 to 10.1

Rough running occasional spikes to 1.5

Segment A 1

Segment B 1

Sense wheel adapt .0007

Misfire detection 0

ISSUES

Not to say that my work was perfect, because I had one weeping perimeter head bolt that wasn't torqued properly, I damaged one of the coolant hoses upon reinstall (new one ordered), broke the stupid plastic AOS coolant coupler near the oil fill tube, and the oil filter housing was not torqued to spec (next time I have some spare cash I'll probably do the spin on adapter, I'm so sick of that stupid plastic housing). Bank 1 was ticking badly upon first start, I thought for the worst that I had to drop it again, but thankfully it was just a loose/bad spark connection. I also improperly routed the throttle cable and as a result the DME was confused about the throttle plate angle at first startup, and the idle was stuck at 1200 RPM. Both variocam actuators actuated properly when activated with the PST2, and power through the range is consistent and smooth.

The only nagging things I am left with which I am somewhat kicking myself is noticing after the fact that the crank pulley appears to have more run out than I would like to see. I will be measuring this run out soon and investigating the possibility of a flat 6 harmonic under-drive pulley or perhaps a new engine. That and I don't think I have the timing 100% spot on, but it is close.

Bank 1 @ TDC

Bank 2 @ TDC

I am also nervous about a potentially poor decision to abstain from loctite usage on the variocam actuator, lifter carrier, and bearing saddles. When I removed those bolts they appeared to be "factory fresh" oily and brand new for lack of a better term. So I decided to just re-torque them to the specific tightening sequence and value. It wouldn't be the end of the world if someone told me I did that wrong and should really consider removing the cam covers again. At least this time I would be able to do the work faster and with much more confidence.

DISCLAIMERS

I AM NOT A MECHANIC. I am a computer professional, and have done most of the work on the cars or boats I've owned or used for the past 20 years. Some of the things I comment on in the photo gallery might be done "incorrectly" or be appalling to some who are in this trade. But, I have to say it got the job done and I'm not afraid to drive my car anymore.

THANKS

First and foremost rennlist and renntech are perhaps the best sources of useful information you can find, since there is not a ton of info about these engines elsewhere, unless you have the money to pay for one of Jake's seminars (which would be totally awesome) or are a Porsche employee. There are several great "DIY" engine drop websites as well, http://www.nutrod.com, http://986fix.com, http://www.oz951.com.../enginedrop.htm, http://101projects.com and Wayne's Boxster book is great as well for M96-01 info, especially for summarizing the cam removal DIY - however it is somewhat "incomplete" as it leaves a few very critical things out such as ensuring proper timing procedure and torque settings are carried out. In the end, nothing can replace the authentic work shop manual. I wouldn't even try to attempt any of this without access to that and a Durametric and/or PST2.

Thanks to all the suppliers, Bob @ http://www.sunsetimports.com, Henry @ http://www.porscheoemparts.com, http://www.pelicanparts.com, http://www.rmeuropean.com, http://www.4wheelsautoparts.com, and http://autoatlanta.com

And certainly THANK YOU PhillipJ, Dharn55, Loren, Don and crew at Riebes machine shop, Dr. Injector, and anyone else who provided any help including those that helped fund this project through the sale of some of my parts!

Now it's time to take a drive!

Edited July 14, 2011 by logray

[jml3p]

That is a fantastic job, the sense of achievement must be great! Will read and look at the photos at the weekend.

Well done Sir

[coleta]

Congregations. And thanks for the great post.

Can you post all the BEFORE numbers from the DME and the injector report if you have them?

Thanks again.

[phillipj]

Awesome job.. I admire you tackling what most of wouldn't. Enjoy your car and I'm glad I could be of help!:clapping:

PhillipJ

[logray]

Can you post all the BEFORE numbers from the DME and the injector report if you have them?

Thanks! I have bits and pieces of the DME numbers, for example cam deviation, rough running values, but some of the others are misplaced.

However, I was not as concerned with the before on the numbers, because my decision to do the rebuild was not based on bad readings. One did not need a computer to determine there was a problem (as detailed by my post). I was mainly concerned once I put it all back together that the numbers would jive with what the factory says they should be at.

That being said, if you think your numbers are off, I encourage you to look at the DME setpoints. Here they are for the 996. http://www.renntech.org/forums/topic/38219-acceptable-rough-running-values

If yours are off, then you can ask questions about what those numbers might mean and how you can try to correct them.

As for the fuel report, here you go:

[coleta]

Hi Logray, Do you have shots of these pics but for bank 2?

(As if you didn’t provide enough pictures :))

Get info, thanks again

Edited July 15, 2011 by coleta

[logray]

Sorry I'm not sure if I have those pictures I probably deleted them. I did take some but they were out of focus or the exposure was bad.

Bank 2 generally had less carbon than bank 1, and mirrored what the plugs looked like.

[coleta]

No worries. Great post

[logray]

500 Mile Report.

The car is a joy to drive. So much power. Idles very smooth too.

When it rains it pours though. Right after I installed the engine I tested the variocam actuators with Durametric. Both banks worked, however shortly thereafter I couldn't activate bank 1 when I tried it a second time and got a P1531 code. I ohmed out the solenoid and it read near 0. Whereas bank 2 read over 13. So out came the engine again to replace the solenoid. Engine installed a second time and I've put 500 miles on the car since.

Oil consumption seems to be near zilch at this point, wheras before I would have blown through perhaps 1/2 quart at 500 miles.

One outstanding problem though. Bank 1 is accumulating more soot in the tailpipe (signifigantly more) than bank 2. In fact, the right tail pipe is pretty much black with soot (I had cleaned during the rebuild) whereas the left tail pipe is basically clean. This problem was devleoping before the top end rebuild and it doesn't seem to have changed afterwards. Yeah yeah, what does soot matter anyways - if the car runs great who cares, right? But I am concerned that the two banks are developing soot at a different rate.

Cylinders were very smooth when I had the heads off. Could not see or feel any imperfections (of course that doesn't mean they weren't oval, which I did not measure...). But I sorta took a gamble the purple smoke (now gone) was going to be the in heads anyways... (which several valve guides were found to be shot).

So thinking perhaps the soot build up could be worn rings on one or more cylinders in bank 1 since I had just done the top end, must be the other end right? The out of spec valve guides and all the valve seals were replaced during the valve job (not to mention 3 way valve cuts to ensure perfect seating)... so pretty confident where the air would leak out...

I decided to do a leakdown and compression test. Warmed up the car and proceeded to get the results. Much to my surprise...

Leakdown (in each cylinder the air was leaking through the oil filler tube indicating worn rings, not a hint of air from the top or bottom end).

1 = 23%, 2 = 24%, 3 = 24%

4 = 25%, 5 = 25%, 6 = 26%

Not too bad for an engine with 75,000 miles on it. Not that good either, but probably not a reason to tear into it again at this point, looks like the rings have a few more miles in them. At least it shows even wear and the engine still performs well.

Compression

1 = 155, 2 = 154, 3 = 150

4 = 149, 5 = 149, 6 = 149

And when pulling the plugs ALL of bank 1's plugs (cyl 1-3) look identical to this.

Whereas ALL of bank 2's plugs look identical to this.

Pulled the headers and the exhaust side of bank 1's head is all black and sooty after only 500 miles already whereas bank 2's head is relatively clean (albeit not sparkling like it was after the valve job).

So now I am a little stumped, perhaps it is due to a fuel delivery problem?

I thought perhaps the MAF could cause this, but then I should see consistency between both banks. Found a great thread on the subject, however again the problem here is with 1 bank and not both.

http://www.renntech.org/forums/topic/21472-fuel-air-mixture

Perhaps it could be O2 sensors, however they are all brand new (and same problem with the old ones).

When I did the rebuild I had all the injectors sent off, tested, cleaned, and orings/filters replaced. I also cleaned the fuel rails as best I could with compressed air - there were no apparent blockages.

I seem to remember that the design of the fuel rails might have changed with later model year cars. Perhaps this is just how the 1999 model M96-01 runs? A little richer on bank 1 than bank 2? Anyone else notice this?

Pulled out the Durametric to log some data. Any more data you would like to see?

At idle and up to about 3000 RPM FRA for bank 1 and 2 is 1.04.

Above 4000 RPM FRA goes to .98 for both banks

TRA for bank 1 is always -0.14 and for bank 2 -0.17

Hot film MAF 1.3 volts at 680 rpm idle, and 17kg air mass. On up to 500kg at 6000 RPM and 3.41 volts. (MAF was cleaned w/CRC cleaner during rebuild).

How do I explain this soot buildup in bank 1 but not bank 2 ???? It's driving me crazy !!!!!!

Brand new AOS dumping oil into the intake on bank 1 ???? (third AOS on this car). I meticulously cleaned all of the AOS tubes and completely overhauled the SAI system to boot.

Then again, perhaps I should just ignore the soot and keep driving it. At least I'm sure that would be the advice of some... but I can't seem to ignore it after sooooo much hard work.

One of my favorite quotes from this great thread is from Macster:

http://forums.rennlist.com/rennforums/997-forum/616049-exhaust-soot-oil-or-fuel.html

"For street cars as long as the engine's running ok, the CEL is not on, flashing, the engine exhibits no untoward behavior, oil consumption is within the allowed range, fuel consumption is in expected range, and coolant is not disappearing into the engine, the exhaust tips could be plaid for all that it matters."

Bank 1 Tail Pipe (looks blacker in person, camera is brightening it up)

Bank 2 Tail Pipe

[wvicary]

I'm not sure on your model year if you have a return-less fuel system or not but if you have a fuel pressure regulator at the engine, what side of the intake manifold does the vacuum line attach?

[logray]

It's a 1999 C2 (with return IIRC).

Vacuum line on bank 1 I think.... (left, drivers, side with soot).

Edited August 25, 2011 by logray

[wvicary]

Is it possible that the fuel pressure regulator is leaking past the diaphragm and the raw fuel drawn into the intake? I had something similar on a VW once..... just something to check.

[logray]

wvicary - It's a thought but I think that vent line actually connects directly into the throttle body? So I think I should see the problem manifest in both banks.

.........news flash.........

:angry::angry::angry::angry::angry::angry:

Could this be related to timing and/or a faulty variocam actuator?

Reason being, shortly after I reinstalled the eninge, I had a P1531. The solenoid/actuator failed to activate using Durametric. The solenoid read near 0 ohms with the multi meter. So I dropped the engine again and replaced the solenoid with a used unit.

After 500 miles hooked up the Durametric and P1531 was stored, but hasn't set the CEL yet. Cleared it, took it for a drive, P1531 set again.

Sh**. Pardon me. This is getting silly. :cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing::cursing:

So, out comes the mutli meter again. The "used" solenoid I put in ohms out fine now.

Swapped cam positions sensors between banks. (PITA)

P1531 (174) code still sets after it's cleared.

What's strange though is now I can activate both banks and the idle changes noticeably. Too bad I don't have a newer Motronic, I could monitor actual angles as well.

Checked the wiring and it is good (in fact I even did some repairs to it after second the engine drop, noticed one of the wires was kinked so I spliced and re-soldered VERY carefully (I do a lot of soldering).

So I am thinking the actuator is faulty at this point???

Perhaps it has been marginal for a long time and is either sticking either open or closed and hasn't been actuating as it should.

Maybe this causes a difference in timing, perhaps leading to slightly different valve opening/closing resulting in less than 100% fuel burn off leading to soot in all of bank 1? Grasping with that theory I suppose.

Or perhaps the used solenoid I installed was also bad or on it's way out.

On a 3.4L does anyone know if the DME is smart enough to disable variocam actuation on both banks if it sees a cam activation issue.. to support my theory above ?

BACK into the engine again after I source some more PARTS. Yay.

Edited August 25, 2011 by logray

[wvicary]

And the mechanical valve timing is correct? What does a vacuum gauge read when connected to intake manifold vacuum?

[logray]

As for measuring the vacuum I can certainly do that however I would believe that since the intake plenum is shared between banks then if there was a problem with the new (third) AOS I've installed should it manifest itself in bank 2 as well? Or perhaps are you saying the proximity of the AOS to bank 1 means it would in theory see more oil than bank 2 if that were the problem?

The timing is as good as I could get it by setting the engine at TDC via crank pulley lock pin, then adjusting the cams so the marks lined up with the cam cover.

I did not use split overlap method nor did I have a genuine timing tool.

However I believe it is very close. Also, issue was present prior to the major work, however I'm not discounting the timing could have been off prior to that (however I did verify timing marks before I opened the engine the first time, but did not use a "timing tool" to insert to see if it was closer to perfect than I got it).

bank 1 before engine removal (with 75k on the clock, presumably set by the factory)

bank 2 before engine removal

Edited August 25, 2011 by logray

[wvicary]

I use the vacuum gauge to determine the engine sealing efficiency. A fluctuating gauge could indicate timing or valve/valve guide problem. Is it possible to post the secondary O2 sensor readings and the catalytic convertor temperatures?

[logray]

Ask and you shall receive wvicary.

Intake vacuum results at idle (38.5 cm Hg = 15.15 in Hg and steady. Not corrected for elevation, test performed at 1800 feet altitude). I plan to get more readings during different scenarios (sweeps of rpms), but it's too hot to work today in the mid 90's here in Northern California.

Crank case vacuum slack tube manometer results (5 inches of water at 680rpm idle).

Bank 1 (cyl 1-3) cat converter temperature (idle) [the bank with the soot in the tailpipe]. I don't think my Durametric can log exhaust temps... not sure.

Bank 2 (cyl 4-6) cat converter temperature (idle)

I apologize for the next set of results. For some reason my Durametric laptop is giving me headaches. I hooked up the PST2 but I couldn't get my screen capture software working so I just took pictures.

Ign timing varied between 5 and 9 ish at idle.

Of course, if you need more data please let me know!

Edited August 27, 2011 by logray

[wvicary]

Everything looks is well within spec at idle but it's interesting how steady the vacuum readings are. My next step would be to monitor camshaft timing and O2 values with the engine under load on a road test. So you don't get bogus secondary O2 or cat convertor reading you'll need to get them up to temp and burn them clean. Drive the vehicle at highway speeds but at a higher RPM- 3500 to 4000 - for approx 20 KM. After this you'll need to check for fault code, clear any that are present and then carry on with the monitoring of the values.

[logray]

OK, took the car for a higher RPM drive, mostly around 3500-4500 RPM for about 20km.

No fault codes (I actually put in my spare DME which hasn't triggered P1531 yet - but I'm still going to swap the actuator and solenoid in bank 1 regardless).

Pretty much the same reading on the vacuum gauge. Here's a new video with some sweeps of RPM.

I've been reading that the quick blips of RPM to 2500 to 4000 ish on most cars should make the gauge quickly go to 0 and then go back up closer to 25 In Hg intake vacuum. Where as I'm only seeing about 20 on the return (equalization).

I'm not familiar with the 996 to know if this is normal or not. In other words if the gauge is accurate and saying that the timing is really late at around 15 inches Hg (or if that is another indicator for worn rings). Or if the sweep thing above is another indicator along with the soot and leakdown/compression results that the rings are actually worn enough to cause this "blow by". or.....

Maybe the "idiot gauge" is right. I've also been reading that late timing can cause a tendancy to burn more oil due to intake vacuum - and perhaps that is what I'm seeing in the form of soot in bank 1's tailpipe?

Also I was doing another leak-down test and noticed my testing rig has a leak in it, so the results I posted earlier are null and void at this point. I'll work on getting better results.

I got my Durametric laptop working again and logged some data at 680 RPM idle again right after the spirited drive. But for some reason I can't get the after cat reading with Durametric - maybe it's an artifact of DME 5.2.2? Maybe I'll send an email to them.

One thing that is a little suspicious below is the ignition timing fluctuating a little, going up above 6 (which is above the factory set points).

While long term adaption FRA is within spec, 1.02 +/- 0.04, TRA shows -0.16 which is out of spec by .05, the factory setpoint is 0.00 +/- 0.1

Edited August 29, 2011 by logray

[wvicary]

Have someone drive the vehicle at highway speeds and at different RPM's while you monitor the O2 and camshaft data. Your vacuum reading seem ok just very steady which might just be the gauge. 18-22" of vacuum is the spec I've always used.

[logray]

Have someone drive the vehicle at highway speeds and at different RPM's while you monitor the O2 and camshaft data. Your vacuum reading seem ok just very steady which might just be the gauge. 18-22" of vacuum is the spec I've always used.

I certainly can do this, however I cannot monitor camshaft actual angles since I have a Motronic 5.2.2. This makes me frustrated sometimes, and wanting to take on a project to convert to motronic 7.2 or build a meter/gauge to monitor things such as actual angles, etc.

The only thing I have to go on is camshaft deviation which is 3 degrees positive at the crank (1.5 positive at the cam) for each bank, so cam timing IS actually a few degrees late, but whether that translates to the vacuum gauge reading or the possibility for the increased oil vacuum through the rings (as I posted about earlier), I don't know. I would guess it would have to be signifigantly more out than just 1.5 degrees for that to come into play.

I think I will get out the slack tube manometer and see if the TDC mark is accurate or not. And possibly I'll try advancing cam timing a little (perhaps a few degrees the other way) to see if the car runs differently (better).

I think I have that right, negative camshaft deviation would be advance cam timing and positive would be retarded right?

Degreeing the cams is another excercise I could do - perhaps the machine marks on the end of the camshaft are not REALLY the center for intake/exhuast valve opening... (still trying to find a way to do this without pulling the heads).

Also you are saying you see 18-22" on a 996?

I think I am the first person in the universe that has posted about using a vacuum gauge to read intake manifold pressure on a Porsche Boxster engine. I've searched literally for hours on end and cannot find ANY data or anyone who has posted what their vacuum gauge reads.

Seems like such a simple thing to do. I wish there was someone with a gauge that could hook it up to their 996 and see what they see, ya know! :rolleyes:

[wvicary]

18-22" is a rule of thumb at my elevation. I often use a vacuum gauge to help find mechanical problems on engine but honestly I'm the only person I know who does so. Even though you are not getting O2 sensor faults I would try and sway the primary sensors side to side and see if the soot still appears on the same bank. It's easy enough to do and will eliminate a O2 sensor that might be biased towards a lean condition. I hope I'm being of some help and not leading you down the garden path.

[logray]

NO that's OK I certainly appreciate the replies wvicary and the advice, not leading me astray! :D

As for the O2 sensors, this condition (soot) was present with old O2 sensors before I removed the heads and had a valve job done. When I reinstalled the heads I put in brand new O2 sensors (4 of them). I may swap them though and see if that has any affect... however at this point I might be resigned to the fact that the soot is from oil, and not fuel. I guess some of me is optimistic and looking for an answer so I won't have to tear the short block down and replace the rings and bearings (and possibly re-bore and re-sleeve).

As a side note I removed the Laso aftermarket H20 pump. There was too much play in the pump's pulley after 500 miles and it was starting to leak around the pulley shaft. Pelican does not even stock them anymore (nor will they stock them again apparently). So I installed the replacement unit from Pierberg. That unit has metallic "like" fins and seems like better quality. Anyhow, H20 pump aside since that has nothing to do with the soot...

Some progress perhaps...

I pulled out the slack tube manometer and installed it in cylinder #1 to determine TRUE TDC. I was pretty astonished how accurate that method is. Considering the next thing I did was install a dial gauge with a probe extension onto the top of the piston and found TDC down to the hundredth of an inch. The mark on the case and crank pulley (and lock pin boss) are remarkably close to true TDC, albeit probably about 1 degree early. This might account for some of the +3 degree at the crank (late?) camshaft deviation value I am reading from Durametric on both banks, since the crank was actually not at TDC yet when the cams were timed, so by the time the crank reaches TDC in a degree or two, the cams are behind the crankshaft a little (edit: wait, maybe that means they are early.... I'll re-read this in the morning). Or perhaps the variocam unit in bank 1 has been misbehaving for a long time but the DME hasn't been reporting it as a problem since it's still "in spec".

Still trying to figure out how I can degree the cams on this engine and get true split overlap timing without tearing the entire thing apart (i.e. with engine installed)... some time this week I hope to swing the timing forward about 6 degrees at the crank, in an attempt to try -3 degree cam timing (early cam timing instead of retarded) and see if that works out better for this engine. Perhaps that will help with the soot situation if it is in fact the following condition is the cause:

"Late cam timing is also a prime cause of excessive oil consumption, especially blue smoke on overrun. This is correctly ascribed to oil being sucked up past the rings, but the real reason is that vacuum on the intake stroke is excessive from the late cam timing." -various sources

Without degreeing the cams and achieving true split overlap, I'm not certain if 3 degrees at the crank means the above quote comes into play (or if it means much grosser timing errors like 6 degrees or higher cam timing).

Edited August 31, 2011 by logray

[coleta]

Logray, what do you mean you used the manometer on cyl 1 to check tdc?

[logray]

You can connect the slack tube manometer into cylinder 1 using a spark tube adapter (like a compression tester). You slowly rotate the crank as it nears TDC, the level of the oil will rise. At that precise moment you mark the degree wheel or case/pulley. You rotate past TDC and at the moment the fluid begins to retract, you mark the degree wheel or case/pulley. You mark the halfway point in between those, and that is your true TDC. I think there are a couple you tubes on the subject and here is a website describing that process.

http://www.cadvision.com/blanchas/54pontiac/tdc.html

The dial indicator was MUCH more accurate though (hundredths of an inch), with a plunger extension resting on the top of the piston head repeat the above test, the halfway point is TDC.

In my engines situation, true TDC was actually just a hair past the TDC mark, so much so that the TDC lock pin in the case boss does not go in.