logray

If any of you have been following my rebuild project, unfortunately my valve job gamble didn't pay off... well not as well as I hoped. While the engine is running really well after just 500 miles since the top end rebuild, I need to address a problem in all of bank 1 (right tailpipe) with oil rapidly forming on plugs and oily soot building up rapidly in bank 1's exhaust ports (but completely absent from bank 2's left tailpipe !?!?!?!), lower than "normal" compression numbers, and leak down past the rings.

I am working to validate these numbers in a couple weeks when I re-test:

Leakdown (through oil filler tube). [bank 1] 1 = 23%, 2 = 24%, 3 = 24% [bank 2] 4 = 25%, 5 = 25%, 6 = 26%
edit: (revised leak down test with better tools reveals only 7%, but low compression still indicates worn rings)
Compression. [bank 1] 1 = 155, 2 = 154, 3 = 150, [bank 2] 4 = 149, 5 = 149, 6 = 149

Assuming those numbers hold true, I'm weighing my options here and could use some help deciding how to move forward.

Option 1.) Drive the car until it starts puking oil out the exhaust. Forget about the soot until it becomes an even more costly problem down the road (more damaged internals, 02 sensors, cat converters, another valve job, etc).

Option 2.) Remove the heads again and measure bore/taper. If the bores and pistons are within spec, continue the tear down and replace crank & rod bearings, thrust washers, piston rings, chains, guide rails, and other hardware inside the short block. Perhaps another $1-2K for DIY on top of what I've already dropped in to the engine ($3500). I could probably manage this financially.

Option 3.) Walk away from the car and take the 15-20k I might get for it to find another 911. I really love the car though and can't see myself doing this.

The following two options mean I'll have to start parting with beloved possessions such as EVOMS intake, carbon fiber steering wheel, carbon fiber shift ****, PST2, roof transport system, !8" Sport Techno Wheels with new Bridgestone RE050A's, Escort Passport 8500 x50 radar detector, etc. etc.

Option 4.) If one or more bores is too oval or worn, send the block off to LN engineering for 3.6L rebore and JE pistons. This would bring my total spend up into the $8500 range.

Option 5.) Sell the M96-01 complete engine, and pickup a reman LS V8 crate engine, then put the money of proceeds of sold items towards the conversion instead of the M96-01.

seanmcr6

Don't get too caught up in the little things. Does it run? Well? Pulls strong...drive nice? Then just drive it and enjoy it.

It's way too easy to get caught up in the minor stuff, but you could spend your whole life trying to fix/make right every little thing and never get it done. It's an old car, it's never going to run like brand new no matter how much money you put into it.

Now if only I could take my own advice, I'd be a happier owner myself

sean

Dharn55

Logray -

Seems strange that the problem is in bank 1 with the numbers you give. The leakdown on that side is lower and the compression is higher. I would expect the opposite if the piston rings were a problem.

You had the valve seals replaced on both sides right?

Could you have a bad head gasket? If you are going to put in the new actuator I sent you you could pull off this head again, Of course you would have to go for new head bolts and head gasket to do this.

A bad AOS would be putting oil into both sides.

Except for the problem with the actuator I would agree to drive it for a while.

Flat6 Innovations

Did you split the case at all? if so what was done with the cylinders and rings?

Did you look closely at the valve guides in the heads? These are known for wear in the 3.4 engines. How about stem seals? Both these issues will create chamber contamination.

With that low of compression and huge leak down all going past the rings I'd say this is a classic cylinder/ring seal issue. Thats the reason why we don't even take that risk and replace cylinders, pistons and rings with updated versions. Been there and done that and its no fun at all.

It won't get any better, thats the cold heard reality of it.. If the leak down numbers were half that much and the compression numbers were at least 185 PSI it might wake its self back up again, but those numbers are very, very poor.

If you really do love the car, do this once and be done with it. If you don't go all the way you'll be throwing good money at bad over and over and over again.

herman maire

Oh no!!!!

its never good when theres a part 2...... part 1 was enough.

I am not sure I understand your compression and leak down results. Is "bank 1" cylinders 1-3 or cylinders 4-6?

I cant see all 6 cylinders being a problem and your compression is evenly low on all 6 cylinders..... I am pretty sure the correct compression for this engine should be in the range of 180-190psi and leak down 3-5% maybe a little more.

I forget exactly what you did in part1 but I remember head work being involved.... Did a reputable shop do the head work?? if not, I think I would bite the bullet and have the heads sent out to a proper shop or at the very least, find a good use head and try that on the problem bank. See if that improves your compression and leak down #'s .

Valve problems can really mess with a engine.

Flat6 Innovations

Its absolutely possible that the engine has lost ring seal on all 6 cylinders- we see this all the time. The cylinder composition of these engines does not yield conventional symptoms or behaviors.

It is possible that the cylinder issues preceded the issues that lead to the heads being removed the first time around.

I have seen engines with as little as 27,000 miles lose ring seal for no reason, having been perfectly maintained and never tracked.
It does seem like there is a missing link here somewhere, knowing what I do about these cylinder heads also raises my eyebrow a bit as well. Like every part of this engine they have some inherent characteristics that must be adhered to during any sort of intervention.

logray

Yeah definatley don't want to understate this problem... after 500 miles the amount of oil fouled plugs and soot accumulation I'm seeing is pretty alarming. My guess is since the valve job was done now the cylinders are sealing up better and the problem with the rings has become even worse or "more apparent".


This is the dilema of what I'm struggling with too, maybe unless someone forgot to install the piston oil rings in bank 1? What I am guessing is that for some reason there was a problem in bank 1 that went on for a long time that also affected the ovality of the cylinders in that bank and therefore perhaps greater ring, piston, or cylinder wear causing more oil to seep through. I know there was an exhuast leak in cylinder #2, and there were 5 valve guides that the shop replaced in that same head.

What is also troublesome here is that after 500 miles the engine only consumed about 1/4 of a quart of oil, probably less. Before the valve job the car was in the 1 quart per 1000 miles club and quickly worsening.

Yes the shop installed all brand new valve stem seals.

No, I did not split the case. And I examined the cylinders for scoring and visible wear and could not find any. I did not measure the cylinders for bore and taper.

The shop measured all of the valve guides. 5 of them were replaced due to being out of tolerance. The valve stem seals were all replaced with brand new (both heads).

This is my vote as well, but I want to send this out to the community to get some second opinions. Thank you for the sound advice as always.

Bank 1 is cylinders 1-3 on the drivers side.

This is what is troubling me as well that the oil seepage is only on bank 1. Bank 2 is still "clean".

I have thought about this, however after the leak down test, I am pretty confident the air was only leaking past the rings and audible through the oil filler neck. I could not hear any air leaking past the intake or exhaust sides.

I also tried advancing cam timing to +6 degrees, thinking that perhaps for some reason the cam timing was too retarded and causing more oil consumption. In the end, the car runs the smoothest and has the most power when cam timing is 0 degrees.

Pulled the exhaust header on bank 2 and do not see oil or soot present. The oil rings have certainly completely lost it on bank 1.

I am pretty sure this is the case, because the soot and heavy oil consumption was present (all in bank 1) prior to heads being removed for a valve job. I gambled that the problem was with valve guides. When the shop found 5 guides that were totally gone (and one guide in #2 ex where could literally wag the valve back and forth in), I was overly optimistic that there was the source of problem. While the valve job did curb the smoke and oil consumption dramatically, I should have been more scientific about cylinder measurement and gone further to crack the case, but my pocket book was burning at that point.

I am thinking the damage might have been started with 1) a very bad leak (large gaping hole really) in the AOS bellows and 2.) a very bad exhaust leak in bank 1, caused by a bowed exhaust header.

If I do decide to pull the heads again, I might bring them back to the shop. They did vacuum and pressure test and said they sealed up properly after the work.

logray

I forgot to mention the intake vacuum gauge readings point towards worn rings as well... of course I'm not familiar if this is a tool you can rely on with the M96-01 (perhaps because of variocam?). The quick throttle openings to 2500-3000 rpm cause it vacuum to go to 0, then after the flap is closed only back up to 19/20 in Hg (instead of 24+ "normal"). And at hot idle, only 15 in Hg and steady (instead of 17-21 for "normal").

Mother

Logray,

For what it is worth my answer is.... if you can swing it.

http://cgi.ebay.com/ebaymotors/Porsc...item2313f4c582

Woops noticed it was Motormeister not sure there reviews where great but at least it is an alternative. Yours sounds pretty good for such low compression.

fasteddie99

Do as Jake says...

...if that is within your budget.

speed rII

Logray,

are the oil extractionpumps at right position? I mean the ones in cyl. heads.
If the oil level in heads are too high, it could cause these symptoms?

dcdrechsel

Difficult decision .Assuming the worst and that cylinders need to be resleeved -looks like there are several options -LNE at $4,000 with pistons ,rings and wrist pins + rebushing connecting rods .I guess cast sleeves also an option -LA Sleeve was quoting $1,500 some time back -potentially could reuse old pistons with new ceramic coating .Problem is pistons rings cost almost as much as new pistons with rings and pins .Which makes new pistons the viable solution .I am guessing $150 a hole .It woulkd be helpful to know how the factory treats cylinders when they rebuild -do they sleeve or rebore ?
The other major expense is the crankshaft -magnufluxing and balancing recopricating mass -don't know the going rate .
I would guess that all in it's a 6,000 to 7,000 project which would yield a very good -reliable engine .

logray

SpeedrII, thanks it's a thought, but the oil extraction pumps (both new) are installed correctly. I've also had them off and back on to alter timing a few times. Also i don't think the pumps would explain why there is soot in cylinders 1-3 but not 4-6. Oil level is one bar above half way mark on the dip stick.

dcdrechesel - I haven't looked into crank balance yet, or if that is something I could safely skip and revisit during the 150,000 mile rebuild.

Edit: I also forgot about injectors (thanks Greg)... mine are the older blue style. They were professionally cleaned and tested along with the valve job. I'm wondering if I would have to go for the newer light green injectors with improved spray pattern (or another p/n) if I go with the 3.6L upgrade.

I've read about heat and other issues with cast iron sleeves. I would consider that a patch versus LNE solution. And as you mention, add in pistons, etc - the LNE option makes the most sense and is the only one I am considering if I decide to rebuild what I've got.

Here's a couple reads on cast iron versus Nikasil.

http://www.911uk.com/viewtopic.php?p=633086

"For example some are now fitting iron liners as a solution. The problem is caused by too high cylinder wall temperatures - and iron liners not only need more clearance but will run hotter wall temperatures (and the ring material is not ideal for iron). The original piston coating seems to last at least 20K more often 60K - but no one knows how long it will last in iron (for a while for sure). Iron liners would be by far the cheapest solution yet all similar performance car manufacturers have gone away from it for good technical reasons and it seems a backward step to return." -Hartech.

(Interesting side note that Hartech also claims to be able to overbore Lokasil without resleeving!)

https://rennlist.com/forums/996-foru...000-miles.html

"members of the industry who are repairing just one sleeve when they make block repairs, the factory also does this as mentioned in the quote above. Generally a ductile iron sleeve is used by the other companies to fix just one bore or individual bores, which generally makes no sense to me, especially considering the differentials in ring capability with the ductile iron Vs. lokisil in the same engine. Lots of these are not working out very well due to the differentials in expansion between the ductile iron sleeve and the parent material, but it is a cheap way to patch up a block for further use. We never do this, LN will not do this even if you request it" - Jake Raby

dcdrechsel

The lack of porsche published specifications/tolerances makes it really tough to make an informed decision .No suprise that Hartech is overboring -the factory has to finish bore the cylinders .That could be a root cause .Even if you pull the heads and check for taper -what is ok and not ok ?Porsche offers several piston sizes but only one ring package (assuming my research is right )which suggests there is room to manuver and that reboring could be an option if Hartech would share the tolerances .

Flat6 Innovations

I have been writing the book on this for the past two years. Literally.

Hartech does it one way, LN and I do it another. Both work better than factory.