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Spyder_Man - I haven't resealed the engine, but I have records of the valve and chain covers being done by the previous owner not so long ago. Regardless, I will replace them again. The engine has weeped a bit of oil during my ownership, but that has not observably increased over the last couple of years.
I hadn't thought to check the engine codes, but it sounds like a good idea. However, can you read codes without the battery or engine in the car?
You'll certainly need to power on the OBD to read its codes. I imagine not having the engine in place with its various sensors wired up would provide you with a whole slew of new CEL codes.
The point remains, I question whether burning oil (unless your engine compression is way off due to worn guides) will result in such a large drop in fuel economy. I'm no expert though so perhaps someone else should chime in on this issue.
If the seals have been replaced then it might be overkill to replace them again. Anyhow from my experience with leaking chain cover gaskets most of the oil is lost while driving so it is hard to tell how much oil is being lost or burnt. GL!
Originally Posted by Steve Weiner-Rennsport Systems
About the guides,.......to date, after doing hundreds of sets of 3.6 heads, I've never seen any 993/964 engine that didn't need guides, unless they were already replaced.
Porsche's fitment at the factory was, in many cases, far too loose and even beyond their own stated wear limits noted right out of the factory manuals. Rennlister Bill Hutchinson's 3K mile 993 C2S guides were well outside of factory tolerances and that was the lowest mile example to date!
Certainly one should remove the lower valve covers and measure/assess the lateral movement of the valves in the guides, but at 77K, I'd wager anyone that they need replacement.
But, but, but, but we've got all these 80-150K milers on original guides changing hands for premium dollars, owners boasting how the engine will go "to infinity, and beyond!"
One of these decades (?) I'll bust down the 42K original RS America race car engine, and will post up what I find for everyone to see. Maybe even make it a tech day.
Porsche's fitment at the factory was, in many cases, far too loose and even beyond their own stated wear limits noted right out of the factory manuals.
So what is factory spec sizing for the valve stems, and valve guide bores, and what is far too loose, and wear limits?
EDIT: Valve Guide Measurement. pdf
.8mm seems awfully sloppy imho...What is the 993 valve stem dim.? Didn't I read that they were cut down for the 993, from 7 to 5mm?. If so, @ 5mm or .19685"; slip fit of the stem through the guide and applying a "spit ball" coefficient expansions of metals; .0015 slip fit clearance of the valve stem to guide bore seems far more than sufficient.
Sine error, factored by measuring distance of the valve head to the guide area and including the raising of 10mm; .015" of deflection would seem significant IMO...Porsche wear limit (using a new valve, mind you) of .8mm or .0314961" of deflection, is yards beyond sloppy in the machinist world!
Vince,
Out of curiosity, do you happen to use Techron, BG44K, or Liqui Moly 2007Jectron, fuel injection/valve cleaner type products just before oil changes? These products would have more effect on injectors and intake valves, but may also help reduce some of the carbon build up in the exhaust area as well. Some also say these type cleaners are complete BS and a waste of $$.
Vince,
Out of curiosity, do you happen to use Techron, BG44K, or Liqui Moly 2007Jectron, fuel injection/valve cleaner type products just before oil changes? These products would have more effect on injectors and intake valves, but may also help reduce some of the carbon build up in the exhaust area as well. Some also say these type cleaners are complete BS and a waste of $$.
I do use Techron. Usually a couple doses between changes.
The point remains, I question whether burning oil (unless your engine compression is way off due to worn guides) will result in such a large drop in fuel economy. I'm no expert though so perhaps someone else should chime in on this issue.
Thanks for pointing this out - wishful thinking on my part to attribute all issues to one cause :-). Several of the O2 sensor cables were worn, so I already ordered 4 new ones as well as new plugs and wires. Also will replace the air filter, fuel filter and caps/rotors too. Hopefully this will take care of it.
That is a vent tube from the clutch housing. I don't understand the benefit of blowing abrasive clutch dust into the air intake with the potential for some of it to ending up in the engine. Also with the OE configuration when one is not careful with the clutch the cabin heat air intake that is in the engine compartment sucks in the fumes and pumps them into the cabin adding that pleasant German Roast Clutch scent, very refreshing! I am considering rerouting the pipe out under the car where it belonged in the first place!
Andy :-)
Came across this. You don't want to re-route that. It actually creates a vacuum in the transimission/clutch that sucks out the clutch dust. If you re-route it, then you will build up dust on the clutch/flywheel.
The German "elves" have a reason for every weird thing on our cars... LoL
If you re-route it, then you will build up dust on the clutch/flywheel.
Ok, but what damage would that do to have "dust" on the clutch, given there are literally millions of standard cars out there without this that seem to work fine? These clutches get pretty dirty (and I have changed several so I know) regardless of this tube.
Perhaps another argument is having a cooling impact because fresh cooler air is drawn into the bell housing, which can cool the clutch (a bit). My cynical side says it's also Porsche's way of make people buy more air filters!
Saw this thread and realized I had a question that never got answered. Would there be any benefit of blasting the exhaust valves and guides with walnut shells similar to what they are doing on the BMW N55 units? See below for before and after.
Saw this thread and realized I had a question that never got answered. Would there be any benefit of blasting the exhaust valves and guides with walnut shells similar to what they are doing on the BMW N55 units? See below for before and after.
Walnut shell blasting is used to control intake deposits in DI engines which affect driveability and emissions. It has no real benefits for the exhaust side where the root cause is oil consumption.
While cleaning all that up can make it look prettier, it doesn't address the excessive clearances between the valve stems and the guides.
Originally Posted by Steve Weiner-Rennsport Systems
Hi Kevin,
Walnut shell blasting is used to control intake deposits in DI engines which affect driveability and emissions. It has no real benefits for the exhaust side where the root cause is oil consumption.
While cleaning all that up can make it look prettier, it doesn't address the excessive clearances between the valve stems and the guides.
Steve,
Not to contradict your statement, but oil consumption is not the root cause; but rather it is an effect of the root and contributing causes that lead to the oil consumption.
In my career, I performed a great deal of cause and effect analysis for the DoD in the aircraft, aerospace, and communications industry...
03-30-2015, 03:09 PM
