Nico911

Hi guys.

I'm wondering if the 997 bore scoring issue is a problem on the 996. I initially thought it was a 997 problem only but I'v been reading all sort of things and I don't know what to think about this pretty scary issue.

Thanks in advance for your inputs.

cdk4219

It’s only an issue until it happens to you, and yes this particular problem is an issue on these and many other plated cylinder aluminum block engines.

motoo344

Can happen to pretty much any 996 or early 997.

Optionman1

i own a 997.2 4s with a 9a1 engine that had bore scoring, it's not just the M96/M97 engines.

wildbilly32

Yes...yes it is a 996 problem too...

Nico911

Ok guys, thank you. I must admit this puts my 996 project down the drain.

Nico911

Well this is scary and surprising, I thought the 997.2 cars don't suffer from this.

TexSquirrel

A new set of Nickies will solve it.

Porschetech3

Unless you have injector/fueling-richness issue ..then Nickies are not immune.

plpete84

Not to derail but what would you say is the Fuel Air Ratio at which point you need to check the injectors. Ideally you want to see 1.00. What about 1.07, 1.10, 1.2?

Mike Murphy

A base 911 starts at $99,200. So a $20k engine rebuild on a 996/997/991 is still well under the cost when new.

Porschetech3

The biggest problem is that DME acually works as if it were two separate three cylinder engines, bank 1 and bank 2, each bank gets the same injector pulse time, and is checked by first/front 02 Sensor for that bank. If one injector on a bank becomes clogged/restricted, the other two injectors for that bank will richen to meet the OVERALL air/fuel ratio target. And vise-versa if one injector leaks/overfuels, the other two will overlean to meet the OVERALL air/fuel ratio target.

As far as air/fuel ratios go, Lamda 1 is "stoichiometric" or "stoich" which is the best ratio for emissions/catalytic converter efficiency (14.7/1), but is neither the best for power or for economy. The best fuel economy is reached when there is enough air to burn all the fuel that is delivered to the cylinder ( 17-19 AFR*), the best power is reached when there is enough fuel to burn all the air that is delivered to the cylinder ( 11-13 AFR*) ****(depending on engine/head design and fuel used).

This is sort of an overview, it can get a lot more technical/detailed than this..

e30rapidic

I just bought a 996 4S with bad bore score and piston slap as a project....

Rebuilding to a Nickies 4.0, having the heads refreshed with minor porting and installing new injectors.....among a list of other stuff a mile long.

Outside of dyno tuning I will be at $13k USD for parts/services.....with my rebuild labor rate of $0/hr

Optionman1

TexSquirrel

Definitely not just a Porsche issue.
Near the end of 2020 while doing a PPI, I diagnosed bore scoring on a 2017 Toyota.
I could see deep scoring through the spark plug hole.
It was just out of warranty, but I sent the original owner back to discuss it with the Toyota dealer.
The scoring started LONG before the warranty expired.
I haven't heard an update.