Silber’s 2002 Boxster S Engine Build
 

All,

Figured I would start a thread to document my project.

Was autocrossing, sudden loss of power. Still ran, but very poorly. Flatbed home. Drained the oil at home, most of the coolant came out the oil drain hole too. Drained the coolant, only coolant came out, so my water hoses are still good.

So, decision time, used motor or rebuild. Can’t find any good low mileage used motors below $5-6,000. Still don’t know exactly what you are getting. Decided to do a hybrid rebuild, steel parts from my engine all “new” low mileage alloy parts. Since I probably have head and/or cylinder damage causing intermix I have bought the following from reputable eBay sellers:

Pair of heads, 29,000 miles, undamaged donor engine.
Set of pistons 37,000 miles, undamaged donor engine.
Engine case, replacement part number, out of 64,000 mile car, assuming lower mileage, no scoring or cylinder damage whatsoever.

New engine parts include but not limited to:
All bolts
Piston Rings
Oil pump
Head gaskets
Rod/main bearings
All new rails
All new injectors
New chain tensioners

Basically building a frankenmotor from low mileage alloy parts, and 116,000 mile steel parts That’s my way of getting a low mileage motor where I know what’s in it. Total cost for all engine parts was right at $5K but I think I’ll end up better off than spending that on a used motor.

I’ve built a few air cooled vw boxers so have some experience going into this, looking forward to getting my car back on the road and hopefully back to autocross.

Where things sit now:

The transaxle is out, engine should come out tomorrow, engine tear down will start after that. I am going to take my time and enjoy the process and make sure I get it right. This thread may not have terribly regular updates, or may have daily updates, just depends on how much free time I can string together, but I will update as I make progress.

Regards,

Silber

I had intermix at 108k and had the head repaired. Still going strong at 156K then comes a 3.8 build. Cleaning out the chocolate milkshake water took a while.

My car had not the best maintenance before I got it, so at 116k I figured most everything inside the engine was tired and could use a refresh. I’ve already bought all the parts, so at least for this go-round, the die is cast.

Silber

Silver, please keep in mind that these cylinders are prone to wear into an oval shape and even by using new rings you may have issues..

I had considered that. I was planning to go with a 3.8 LN Nickies rebuild for that reason. Thing is, I just cannot afford that. So, I found an engine case that I think has less than 30,000 miles on it and figure it is going to break into the new rings all right, and people seem to get well over 100,000 miles out of a block. By that math this block should have maybe 70,000 good miles left.

If it doesn’t work out I made a gamble and lost but I am reasonably confident if I don’t screw up the rebuild it will give me enough miles of fun to be worth it.

Silber

The issue with these blocks is that the cylinders and rings wear together, leaving that as the cylinders "ovalize (is this a word?)" so do the rings. So, mixing and matching, even with a low mileage block, may be problematic as new rings will not seat properly.

Do you have access to a machine shop? The first thing I would do is have someone reliable to measure out your cylinder specs. If they're still round, proceed with build. If not, abandon all hope of success without bore and sleeve.

Sent from my SM-G970U1 using Tapatalk

+1. No sense building it if your cylinders are tapered and oval. You will end up with crappy ring seal and excessive crankcase pressure. Better to get the pistons (with rings) from the block halves, assuming they were numbered and use that than try to get new rings to seal

Engine is out!
https://adobe.ly/3BVvP3q
https://adobe.ly/3tscKmg

Beginning to reconsider my decision not to go 3.8. Might make sense to save up a while and delay the project in order to get a better result.

Going to start the tear down and see what I find, make final decisions once I see what I’ve got.

Silber

Upon close inspection, my low mileage case has a gouge in #3 cylinder rendering it unusable.

So, I am returning all the re-ring specific parts (block, pistons, rings, etc) now. Going to get the heads off and if there is no damage to my short block, put the heads on. If the short block is in any way damaged, then do a full tear down and save up for a 3.8 build.

Glad I posted this, the responses really took some wind out of my sails, but that seems to have been a good thing.

Regards,

Silber

yea, thats what really sucks about these engines. There is really no way to soundly rebuild them unless you find a unicorn with round unscored bores or you go to sleeves. The rest of the stuff isn't hatefully expensive (but damn there are a lot of ancillaries and gaskets), but having to drop $5k to sleeve them blows.

Quadcammer, yes sleeving the block is expensive, but I believe that the kit of the 3.8 LN Nickies, include the sleeves, new pistons and rings..

It does. But for instance, I recently rebuilt the S52 Inline 6 in our M3 endurance car, and a set of JE pistons, with Eagle rods, was $1250. Boring and honing the cylinders cost about $350.

So you're talking roughly $1200 for the BMW motor, vs $5k for the M96. Not earth shattering, but not chump change either.

And then there is the wait for the LN Nickies. Mine took 6 months. Waiting to see how long Husker Boxster's Cayman engine takes to get LN Nickies since his is currently there. The Nickies need to be plated after they are installed, that is what takes so long, very few platers in the country that can do this work.

Well, I’ve now got the engine on a stand and ready for disassembly. I have set aside this evening to pull the 1-3 head.

I’m fairly certain that something went wrong on #2 (melted spark plug boot, spark plug stuck in the head) so I’m guessing a 75% chance piston is melted or Dchunk, 25% chance head issue that left the short block usable as-is.

Will report here with pictures when it’s off.

Silber

Well that was quick. I pulled the intake and found all this stuff in there. Pieces of head, valve, and piston ring.

https://adobe.ly/2XhCdDa

Once I got the intake off I could look down and it was indeed number two that had failed. At first glance, it looked like the cylinder walls were not damaged. Now I’m not so sure, I got out my El cheapo borescope, and it looks like the wrist pin is missing so the rod was moving free in the cylinder smashing the remains of the piston. Mainly I’m concerned about the crank and crank carrier, if those are the only thing salvageable out of this engine I will be ok with that.

At this point I am absolutely 100% certain this engine is not re-buildable just by putting heads on it. Looks like it’s a 3.8 for me.

Silber

that case is definitely not going to be usable. Crank and carrier are crucial although I suppose you may be able to align hone the carrier to work with a different crank or vice versa.

The low mileage case I bought to rebuild had cylinder damage that made it unusable for a re-ring, but not enough damage it wouldn’t be rebuildable by LN. The seller let me keep it so I’ll probably give that one to LN.

Looking with the bore scope, the rod was not visibly bent, and there was no visible damage to the crank carrier. I am hoping I got lucky, but will definitely check everything!

Silber

I think I figured out what killed my engine. And it’s a new failure mode that I hadn’t heard of before.

If you look closely at one of the intake ports where the cylinder didn’t have an issue, you can see that there’s a bright line of clean aluminum where the gasket was.

https://adobe.ly/3lzIlzc

If you look at number 2, the cylinder that failed, the bright clean line goes all 3/4 of the way around but closest to the center of the engine there’s dirt all across the clean line. Looks like there was a vacuum leak from the plastic intake manifold warping. All the bolts were tight, nothing was loose. Yet there was not a good seal.

https://adobe.ly/3Cbidkw

Since I was a autocrossing the car, there was sustained high rpm usage so that vacuum leak caused cylinder 2 to to get hot enough to drop a valve.

How do I prevent this from happening again? Not sure yet, I’m going to see if the new seals are thicker than the old ones perhaps, I might run some extra sealant around outside the factory seals, not inside. I’ll probably trash that intake manifold and buy another used one but what’s to say the new one won’t be already warped or warp after I put it on.

Food for thought.

Silber

I would think that if what you describe really happened then exhaust valves would be burnt not dropped.
You can burn hell out of valves and never drop them. I would want more "proof" that a vacuum leak caused a valve to drop before I went that route.

You might be right, I don’t think it will hurt anything to make sure that the intake seals completely.

However, Something caused #2 to self destruct. The spark plug got so hot only on that cylinder such that the boot partially melted and stuck to it.

That much heat is usually caused by overly lean, caused by too much air or not enough fuel, or a combination of the two.

I already bought 6 new injectors, so covered not enough fuel. Making sure the intake seals should cover too much air. Think that should keep the new motor from suffering the same fate, any thoughts?

Regards,

Steve