Steve Weiner-Rennsport Systems

I'd concur with Brant; these engines hold sufficient oil that dilution is not an issue unless one does multiple fuel treatments between oil changes.

Naturally, some of this depends how often your oil changes are performed.

964Q

I understand these engines do not like to be brought up to redline in risk of breaking retainers and valve float?

KaiB

We're all in serious trouble then.

Please re-check your sources.

Steve Weiner-Rennsport Systems

Kai is right; somebody misinformed you and left out all the context,..

These, like ALL engines, do not like to be over-revved and Porsche provided the rev limiter to keep that from happening. Remember though, it will not function with a missed downshift and that can place the valve train at risk.

The stock springs and retainers are safe to the redline; 6750 RPM (as long as one doesn't miss a downshift). If the valves do float for any reason, that can break retainers (they are sintered metal) and/or bend valves.

One thing,......valve springs do fatigue over time and lose some seat pressure which lowers the threshold of valve float. For this reason, we oftentimes install new springs (OEM or race, depending on application) when the heads are rebuilt, especially for track use.

KaiB

If I may without seeming pendantic.

As an instructor, I see this all too often. The tendency for many is to downshift too early, thus forcing the engine into a rpm range it does not want to see - and upsetting the cars balance. This is rough on the engine (as discussed) and improper on the track.

Brake, brake, brake...and then downshift - the tendency is to downshift just as braking starts...don't do it. Merely relax, brake, watch (feel) the rpms calm down, and then downshift into the proper exit gear.

Your engine will certainly thank you, and those entrance waggles should lessen over time.

964Q

This was from my memory, but after digging around a bit, this is what I found. I guess more of a rod bolt issue. Not sure if street driven cars have to worry about this as high RPM is not sustained as much as race cars. Thoughts anyone?

http://rennsportsystems.com/3-6-engines/

http://forums.pelicanparts.com/911-e...ottom-end.html

964Q

Kai and Steve, thanks for the explanation. I love learning about these cars, especially from seasoned Porsche guys who race these machines.

KaiB

Beyond the valve train issue, every time a engine is forced into a mechanical over-rev situation, additional non-compressive forces act upon the rod bolts (i.e. stretching forces)...over time these add up, the bolts themselves elongate, and a bearing can slip.

The resultant "catastrophic" failure usually involves a rod through the case (and oil on the track, not fun)

964Q

Got it, thanks for the clarification.

August West

Back to original poster...what numbers did the dyno give you?

philchil

Dyno numbers...242 hp and 228 torque rear wheels...to the ground

Alan G.

Techron used to avise changing the oil after use, but they changed at some point. I just kind of got onto the habit of running a can through on the last 3/4 fill up. That helped but, I still have more carbon than I would have expected.

Unfortunatly I was back into an engine I had redone 2 years 7,000 miles ago. half of the miles were track, still stock motronic with a cat, and I still had some bullitproof build up on the heads and pistons. It must have something to do with EPA's special Northeast Gas Blend. I'm not complaining, at least we can 93 Street Gas. I only used name brand Super from stations that move high volumes of super. I expected much less.

I'll probably use some more regularly to see if it improves, but hopefully I'll never have to look at it again. It's good for the engine to see red line at least ocassionaly, but its probably more important to get the car through full heat cycles regularly. That said, you are not going to hurt these beasts by driving them easy.