991.1 Engine swap/rebuild

[nmorris1]

My 991.1 2015 GTS burnt an exhaust valve at 26K miles and careful scoping has revealed most of the cylinders have some form of bore score, so the engine has had it. After a failed attempt at getting an factory refurbished engine swap (Porsche no longer have them), I've decided to swap it out myself and then rebuild the old one. I'm documenting the rebuild here if you are interested.

 

[595triple]

Sorry to hear about your trouble. Pity you did not have a warranty to drop this in Porsches lap.

As I am currently in the process of an engine rebuild of a 3.5 Aircooled race engine, that when stripped was discovered to have suffered from poor maintenance, I feel your pain.

One thing I have learnt, fortunatley not to my cost, is that having bores reconditioned is not straightforward. Many offer such services but few can do it properly. Mine are Nikasil but yours are Alusil in a late MA1/03 engine. Apparently Alusil can be reconditioned but its a very specialist job and would need oversize pistons. It seems Hartech know a bit about this for the 991. It may be worth contacting them unless you have already decided to buy new barrels.

 

[Gizlaroc]

2 of my customers have now had scoring on their 3.8 991.

The first one I thought nothing of it, thought maybe it was a mis diagnosis or something, but another one has just said to me this morning that his 2015 GTS has bore scoring. The first one was also a 2015 GTS too, albeit a cab.

Now this might be different to the earlier cars, as in how it happens is different, but that is two people with a 3.8 with the issue. I don't know anyone else with that engine, 2 out of 2 is not great.


I only found this thread as I was searching for info on scoring on the MA1 after he came in.

I asked if the scoring was all the way round the cylinder, he didn't know but said he will try and get the images. I think the tolerances are too tight on these and you get cylinder shrink?


Do you think it is a problem with the cars with the power kit?
More torque down low means the car is laboured more?
Same reason the tip 996 3.6 and 997's seemed to get more scoring than the manuals?


Just about to swap my rebuilt 997 for a 991 3.8S, so this is a bit of a concern. Or are the numbers so small it really doesn't need to be?

 

[Motorhead]

Porsche has adopted a plasma spraying technique to coat the bores on the 991.2 turbo engines and on the 718s [turbo and nasp]. I wonder if the technique could be used to recover the bores on the OP’s 991?

Jeff