Boxster engine rebuild specs source, tried Bentley manual

Bussmuggler · 12-26-2007, 07:05 AM

Hello all,

Is anyone aware of any resource for rebuild specs for an early Boxster? I picked up a 99 with a spun rod bearing over the summer. The Bentley manual goes about as deep as putting on valve cover gaskets...no info in the internals. A real bummer after spending almost a $100.00 on it. Thought to it's credit, there is a good section on letting out children who are stuck in the trunk!

I've seen more and more info and photos of Boxster builds online, but am unaware of any detailed engine info. Any help appreciated!

racer · 12-26-2007, 12:53 PM

That's the problem with these cars. The early motors were simply returned to Porsche and a crate motor was sent to replace them. Only in the past 2 years or so, does it seem folks are tearing these motors apart and learning about them. Sorry I can't direct you to a source.. but I feel your frustration.

BoxsterGT · 12-26-2007, 01:39 PM

One problem is the expense of the special tools needed.
When you can buy a NEW 3.4/3.6 crate motor for $10k, no one wants to fix their original.
Used motors sell for $3k - $4k, and it cost that much for the special tools.
Just my 02 cents.
Len

Britwrench · 12-26-2007, 05:29 PM

A "99 is the "early" type of engine, as the previous poster said, who wants to repair them?
Buy the Porsche reman unit that has all the updated already installed that you would have needed, and a two year warranty.

Bussmuggler · 12-27-2007, 07:56 AM

For starters, I don't have 10G's for a remanufactured Boxster motor with warranty. If I did, I sure wouldn't put in a 2.5.

I'm not sure what kind of "special tools" you are referring to as the ****ty Bentley manual doesn't show so much as the crank! That being said, I'm pretty confident in my mechanical skills and tools and refuse to be intimidated by this project. If I run into something I can't do, the good guys at German Motorcraft are there to help me out.

The Boxty was on track when it developed a rod knock, (sounds more like a ticking lifter, really). It was towed back to my buddy's Porsche shop where they removed the oil filter and cut it apart. It looked like a little gold mine in there, well maybe copper. More than likely a rod bearing. Since the car has about 90K on it, this was my plan:

Tear down the motor and replace all the bearings. Find the culprit rod and see if the set can be rebuilt. If not, get a new set of Porsche rods, Carillos or find one replacement rod that matches the others. Have the cylinders honed and put on fresh rings. Have the valves ground and the heads freshened up, maybe a bit of port work though the ports are probably matched and butter smooth already. Polish the crank and have the whole mess rebalanced at our local machine shop. Put on a new timing chain and a clutch. Granted, I haven't even started the project so I may run across some other jive. I think I can do the whole job for about 2G's or even less if all goes well.

One thing I did find out in the Benley manual is that the rods are forged in one piece with the cap and the other end. They are machined then lazer engraved at the mating point. They are then cracked and the resulting cracked joint is the new mating surface for the rod halves. No shuffle pins to align the rod halves, only the undulated surface of the cracked joint. A neat idea, but I dont see how these can be rebuilt as when you surface the mating area, the fit of the cracked mating surface is gone. Built in obsolescence! Thanks Porsche!

So, back to my original question; where do I get torque specs, etc... for my build?

tortoise944 · 12-29-2007, 05:45 PM

Everything I have read about the 2.5L M96 engine that the boxster runs with seems to imply that you can do a top end rebuild but if you have cyl or piston issues you buy a new or used replacement engine.

The cyls have a LOKASIL liner in them that prevents any kind of bore or other refurbishment as that liner is very very thin. In fact, the '99MY boxsters with the slipped sleeve issues were on engines that Porsche themselves tried to rebuild due to their factory having a major production issue. These engines had upto a 50% failure rate even with the factory trying to replace these sleeves in their own manufacturing facilities. They also did some one piece casting work that makes replacing even the intermediate shaft more expensive then replacing the whole engine as they cast the bearings for it into the block directly in one piece. So, the new boxsters with the IMS failures all must have engine replacements as its too expensive to repair.

These engines were supposed to be throw aways if anything major happens to them.

GL!

Bussmuggler · 12-30-2007, 10:00 AM

Thanks for the info.

911quest · 11:43 AM

You might find this interesting....What specs are you needing I can get them for you

Not 911 but close.....

Bussmuggler · 12-31-2007, 02:47 PM

Tony,

Thanks for the link. Your teardown thread looks to be full of good info. What is your intention with the motor? A rebuild or just a tutorial on disassembly? It looks relatively straight-forward with no exotic tools so far. I'm curious to see what you come across in the bottom end. I'll be staying tuned.

As far as specs, I'm mainly looking for torque values for reassembly as well as specs for the crank, rods, pistons and bores. Just trying to get my ducks in a row before digging in.

911quest · 12-31-2007, 02:55 PM

Basically for tutorial purpose's I put it back together and have it my garage. Here are the basic tools that you might need I think you could work around a few of them.

The pin is for rotating the crank the only one I see that you would have to is the fixture for the cam timing,