relinuca

My beloved '99 996 has popped its engine. In considering getting a Porsche re-man'd. engine., rather than re-building the original engine, no one seems to know how many and which internal parts will be brand new vs. re-used old parts. Some sources say all Porsche re-man'd engines use new blocks.

Given Porsche's well earned commitment to maintaining documentation, I suspect Porsche knows the answer. So why not offer it to the customer.

relinuca
Porsches Forever (or
until the money runs out )

cds72911

I can’t answer your question. I’ve read things here that align with what you are saying.

What was the failure? Are your heads still good? If so, a factory long block will get you back in the game for reasonable money. They allegedly have the most current updates (including the later large IMS bearing).

I’ve had good luck with salvage motors, but they come with risk. Who knows whether the used motor is on it’s last legs too? It does seem to be the most cost effective, especially if you can do the R&R yourself.

Someone is bound to post about how the factory motor has some huge number of failure modes and going with a factory long block doesn’t address that. How seriously you take that is up to you.

If you love your specific vehicle (sentimental, low mileage, perfect optons, lots of desirable upgrades, etc.), money is not an object, and you have time to wait to get on their schedule, Flat Six seems like the way to go. You could buy another 996 for what you’ll pay, but on the other hand, their builds address a ton of weak spots on the engines. And you can bump displacement up at the same time for additional gains. If I could afford to, this is the way I’d want to go...

dporto

I would (and did) opt for something with "Nickies"... Bore scoring is probably the most common mode of engine failure and the stock Porsche engines do nothing to address the problem. Caveat Emptor!

Imo000

How do you know that? Has anyone looked and checked the new shortblock that Porsche now offers? Word on the street is that it's all new components but that is just what I heard.

Imo000

Short block, not long block. Long block includes the heads too, short block is everything that's inside the block but without the heads.

Porschetech3

All of the factory "re-man" short blocks I have seen look to me to be all new parts at a "re-man" price. Charles Navarra at LNE who has probably seen more of these than I have says the same thing, he may have even disassembled a few of them to look inside, I never have.

Porsche updates many many parts all the time with no press release or mention, the only indication that a part has been updated is the part number has changed by one number at the end. A part ending in 00 is the first design, 01 first revision, 02 revision, ect. It is not unusual to see parts revised 5-6 times. Sometimes these changes are the materials and you can't tell, sometimes you can, sometimes the look is different, sometimes a different vendor is contracted to start making the part and get a revised part number.

The re-man 3.4 short block sells for $6300 with the latest available parts, and is not prone to bore score as much as later engines. To me it would be a no brainer to use this and rebuild your heads and install. If you have an acceptable core that is, I think the core charge is $2200?..Unless of course money is no object, then a $25k JR motor is the right choice.

Charles Navarro

The shortblocks are indeed new, but as far as the cylinders are concerned, they are not an updated design or material nor are they less likely to score. I have been told by other shop owners they have seen new or reman longblocks and even the most current shortblocks have failed with scored bores.

One question I cannot answer is whether Kolbenschmidt updated to the Lokasil II process or they retained the Lokasil I process that the M96 block was based off of. The difference being Lokasil II has higher levels of Silicon than Lokasil I.

I am currently working with Driven to come up with a possible oil additive to help with scoring issues based off of some recent research I've been doing and many research papers I've scoured over. There are actually an inordinate number of papers on scoring with hypereutectic Al bores.

Charles Navarro

Although I cannot verify this information (I do have several emails out that I do not expect to get responses to), but there is also a Lokasil III process that was introduced with the 987/997. As 3.8s seem to be the worse offenders for scored bores historically, I don't think the Lokasil III process is any better than the II or I.

The Lokasil II process was introduced with the 2002 3.6, so with that said, I think the Lokasil I process was the best with regards to scoring (but worse for cracking) as found in the 2.5, 2.7/3.2 through 2002, and the 3.4 in the 996.

https://www.motor-talk.de/forum/moto...19.html?page=5

NuttyProfessor

Oh goodness. Sorry to hear that about your car. What in the world cause the failure?

Porschetech3

Seems I remember reading something about a Lokasil III(?) in my stack of Porsche Technical literature, I assume it is mainly a higher silicon content >30%?

I've read a lot of research papers on hyper-eutectic aluminum/silicon cylinders bores, and it looks like they are here to stay from the OEM manufacturers.

The higher silicon content of Loksil II (and even higher in Lokasil III ?) would make them higher tensile strength, but will also keep them from expanding as much with heat, which may be why they are more prone to bore score. Basically, the piston heats up first and fastest, the cylinder with highest silicon content will not expand as fast or as far, the clearance that is already very tightly set at the factory becomes zero.

Also from the research papers I have read that test piston coatings for hyper-eutectic aluminum/silicon bores, the best coatings are iron and nickel-phosphorus-boron-nitride (Ni-P-BN) .

The iron piston coating was used with Lokasil I, and a Graphite (Graphal) coating was used on Lokasil II and Lokasil III (?). If I ever repair another one of my cylinders/pistons, the piston will get the Nickel-Phosphorus-Boron-Nitride coating., as Nickel is the strongest of non-ferrous metals.

Of course these are just my opinions and are subject to change with more/new information.

Splitting Atoms

Is the problem with the piston diameter or the ring gap? I know with highly boosted turbo engines, the ring gap is very large due to the higher piston temperatures.

Imo000

Did the piston to cylinder clearances remained the same too and the shape of the piston remained unchanged as well?

docmirror

Most discussion here focuses on the re-man engine. "Re-manufactured" is not an easily defined, or universally acknowledge industry term. If Porsche will not disclose what the 're-man' includes as new, and used but within tolerance, I would be wary. For example, a Re-man engine from Continental for an airplane engine includes a list of every part in the engine, and the source. Some might be amazed at how little is actually 'new', aside from bearings, rings, bushings, seals.

Now to rebuilt. Again, an ill-defined industry term. There are millions of engines 'rebuilt' in Mexico(likely not 996 flavor), and there, anything that can meet the factory tolerance can be re-used. including piston rings. Can one imagine a 'rebuilt' engine with used piston rings? I will tell you honestly that I've taken a SBC fresh rebuild apart and found exactly that. What I want to get across is that the rebuilding process must be understood, watched, verified, and tested by the buyer, the rebuilder, and the inspector. Certainly if there is damage to a case, it can't be re-used right? Wrong. Cases are welded and put back in to service all the time. What about new pistons? If the old piston still fits in the bore and meets the limits for clearance, technically it can be reused.

Which brings up the question of 'limits'. There are two that are important. New limits, and wear limits. All engine rebuilders know this, and will not necessarily tell you what they are going to do. So, you'll hear a statement like: 'well, if the original pistons mic out ok, we'll reuse them'. Nooooooooo!!! Just because they meet or don't exceed the wear limits does not mean they are ok to re-use. Pistons are ALWAYS a wear item. but - rebuilders install used pistons all the time. What about cams? In the 996, cams don't wear that bad. But they do wear. Are you getting new cams? Are you getting re-ground cams? If re-ground, are they heat treated right?

Rebuild of an engine can mean a million different things. So, it's very hard to say which should be chosen until we know the shop, their skill set, the materials list, and the cost and warranty of a 'rebuilt' engine. Heck, I can take an engine down, clean it well, put in new rings, a valve job, new seals, and call it rebuild. In the tractor world they even have a kit called an 'in frame' engine rebuild. I kid you not, check it out. The difference is in what is included. New cylinder liners? Probably not for an in-frame kit. New pistons? Hard to say, maybe just rings, bearings, seals/gaskets.

Know exactly what you are getting. NOT based on 'if they look or mic ok'.

Splitting Atoms

For the Porsche M96 "rebuilt" engines being discussed, the engines that have been disassembled by the experts have been found to have all new parts. This makes sense to me since it is probably more economical, with fewer potential liability issues, for Porsche to use all new parts. In Mexico where labor rates are low, it is more economical to have workers clean, measure, and match sets of parts during the assembly process. They can then sell it as cheap as possible, and Americans love cheap.

What interests me most about this thread are the differences in manufacturing and materials that impact the potential for bore scoring. It appears that the earliest cylinders, combined with the earliest pistons, had the lowest probability of scoring. Based on my observations in the forums, it does appear that scoring is more likely to occur in the 996.2 and 997.1. There may also be a geometry factor (less lateral force) associated with the smaller cylinder and piston diameters of the 3.4 versus 3.6 and 3.8.

docmirror

Well, I will defer to those with more experience in the M96 rebuilding world, however - a reliance on the word 'experts' is usually an indication of weak sauce. If you are speaking for yourself, then say so, if speaking for others, I would be concerned that 'experts' often disagree, sometimes vehemently. And, what is the source of these 'rebuilt' engines? Surely not from Porsche as that would be categorized as "re-manufactured", being that the engine came from the mfg of the original product. did you mean 're-man' or 'rebuilt'? I can hire Harv down at H&H import machine to rebuild my engine. How would an expert know it came from there? Or what was inside, after 200 hours of use?