993RS

I would seriously consider having the valve timing checked out by a competent Porsche specialist. If not properly set, it can easily cost you 20 hp. Lots of cars out there with poor and/or unbalanced (between the cylinder banks) valve timing.

Potentially the cheapest way to gain hp.

993RS

Cost? Quote from my garage: $300. for the measurement, then, if needed, around $600-800. for the corrective measures...

Christer

or you can have it done when you totally rebuild your engine to race spec....thats much cheaper....

forklift

I am doing a major service every year including valve adjustment because of the track miles. Right now this is being done in addition to fixing the oil leak. I might re-name my car the Exxon Valdez!

Caveman

Stupid question - so is the valve timing covered by the major inspection?

993RS

No it isn't.

Caveman

Phil,

I just noticed that you have a Cargraphic exhaust. How does that sound? If you have any experience of the RSR exhaust, how do the two compare?

Cheers,

David

forklift

The valve adjustment is needed on 964s on every major service and priced accordingly. I would think you would have to pay extra w/ a 993, but not sure.

993RS

It was on the car when I bought it (it was part of a power kit installed by the previous owner consisting of the cargraphic exhaust, special air filter and a cargraphic chip). Sounds great. No experience with the RSR exhaust.

Adrienne

Okay, I do fear sounding like a complete idiot, but not as much as I fear having bad timing. So, my question: I thought 96 and younger 993s did not need valve timing adjustment because those cars have varioram or it's automatically timed by the computer. Is that true or do I have my facts mixed up? I notice your car is a 95, which does not have varioram, correct? Is that why yours is adjusted?

993RS

Adrienne,
There is no such thing as a dumb question. I knew nothing about this issue a week ago.

First of all, the '95 model was my old car. My "new" car is a '96. The issue here is how the motor left the factory. When the motor is finished, they run it for over an hour, dyno it and look to see if it lies within the accepted deviation range (10%, I believe). Unfortunately, there are chances you might have a motor in the lower range, delivering quite a bit less than quoted by Porsche.

Varioram and the ecu unit control the flow of gasoline, etc. but they can not control the way the motor is physically configured. If when running, the mechanical components are not set up right, you will not get the valves lifting the right amount at the right time. This is the issue: the way the mechanical parts are set up.

It is, according to my mechanic, not just an issue of hp loss, but responsiveness of the motor as well. If the timing is off, the motor will seem a bit sluggish....

chris walrod

Phil answered this question well. Boxer engines such as Porsche's, rely on basically two separate engines connected at the crankshaft, which rely on symmetric compression, aspiration, valve timing etc. for best results. Having disimilar valve timing will hurt the engines harmony ,so to speak, causing rough idle with other than optimal power output. Much like a dual carb setup that is out of sync.

Since the 993 camshaft chainwheels rely on friction fastening, I would think over time there is the possibility of one (or both) slipping. I am sure the efforts Porsche went through to establish consistent power output involved setting these cams to the best of their ability, within a predetermined tolerance of coarse.

This is a great thread you started Phil, BTW

Father of 3

Adrienne:

All 993s have self adjusting valves, wheras 964s and prior versions of 911s did not, hence the need to have valve jobs at major maintenance intervals. There is no NEED to have valves adjusted but, as others have stated, even within factory spec, your motor could be off, therefore depriving you of potential HP and torque. Balancing and blueprinting a motor is much the same, bringing the motor to the factory spec, not just within tolerances. Varioram will have no impact on the need or not to have valves adjusted.

Does that help? If I'm wrong anywhere, others, I'm sure will correct me. Dave?

Then of course there is variocam, or is that vanos?

Eyal 951

have your throttle pedals checked to make sure when you say WOT, it really is WOT... I've seen this issue on more thenone 993.
~Eyal

Adrienne

Thanks for the info. That makes a little more sense now.

I'll add this to my car's ever-increasing to-do list.