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Last month I purchased a very cheap but running core motor that I have plans to rebuild at some point. I took some pictures as I dug in so I thought I would share. This motor was pulled from a 1999 C2 that had 200k miles on the chassis. The motor is a factory re-manufactured engine so who know how many miles this engine actually has on it.
It didn't take long to find what was wrong with this motor.
1999 996 3.4 factory re-manufactured engine. Just removed the exhaust system.
Tore down everything to get ready to pull a head off.
hmmmmmm...........#1 cylinders exhaust port looks a little wet. I wonder what we will find.
FYI, if you have a fuel jug laying around you can use the fuel hose and 3/4 inch threaded hose connector as a spark plug tube puller.
All done. Cheap and easy.
Valve cover off. Looks good so far.
Cams are out. Removing the lifter cage.
Head is off. #1 looks too shiny and #2 and #3 are really filled with carbon.
Motor with the 1-2-3 head removed.
Cylinder #1 looks like it sucked something in at one point.
No surprise here. Looks like some bore scoring and the beginnings of the dreaded D-Chunk.
This is as far as I got today, but plan to start working on the other side tomorrow. Hopefully the heads and crank will test out OK so I can use them for a motor build in the future.
Just thought I would share.
Last edited by sb3; 03-18-2019 at 12:03 PM.
Reason: formatting
Caught just in time. I hear Nickies calling.
Captian Obvious says “It looks to me like #1 piston has been steam cleaned, likely by coolant leaking into the cylinder. Piston showing signs of detonation.”
couls be a fun, if expensive rebuild.
I got it as a complete running unit for $1500 usd. If the heads and crank check out I think I made out ok. The plan is to get some nickies and do a 3.8 conversion at some point.
I got it as a complete running unit for $1500 usd. If the heads and crank check out I think I made out ok. The plan is to get some nickies and do a 3.8 conversion at some point.
Such a shame that this engine was a desperately rushed design.
Not sure I buy this argument. The engine already had successful usage in the Boxster. The problems stem from one bad bearing and using a really large bore, and short rods in a very compact engine. Designing engines that make 100hp/liter in naturally aspirated guise is never easy. Then expecting them to live forever with a full warranty is asking a lot.
Add to it that Porsche is a much smaller automaker with less RnD dollars and test history, things will happen. Every generation of engine ever made by any auto maker has it’s weaknesses. You know what they are now and you know the available options to address them.
Not sure I buy this argument. The engine already had successful usage in the Boxster. The problems stem from one bad bearing and using a really large bore, and short rods in a very compact engine. Designing engines that make 100hp/liter in naturally aspirated guise is never easy. Then expecting them to live forever with a full warranty is asking a lot.
Add to it that Porsche is a much smaller automaker with less RnD dollars and test history, things will happen. Every generation of engine ever made by any auto maker has it’s weaknesses. You know what they are now and you know the available options to address them.
Fair, though the 9A1 checks those boxes, as does the Mezger.
Porsche was failing during the reign of the 993, and didn't have the R&D dollars to ensure the quality of their engine. They could have fitted a pressure fed plain bearing instead of the sealed system they chose. An 8 percent total failure rate is too damn high. Thankfully we now have retrofit kits.
Engine failures aside, the 996 is a fantastic chassis, even shedding 100 pounds compared to the illustrious 993.
Looks like a classic case of a leaky injector on Cyl#1 causing the bore scoring - hence the unusually clean piston top (that scoring is also really high in the cylinder which I think is also unusual). As for the crack - who knows, probably a combination of factors. Was there any oil intermix with this engine? It seems like there is more going on than meets the eye. I would guess that this engine wasn't well maintained (at least in the last 10 -20k miles...). Good luck with it - I'll be following
Yesterday, I continued pulling off the 4-6 bank head. The exhaust ports looked good so I didn't expect to see anything as drastic as what was found on the other side.
Got to use my 'custom' spark plug tube puller again. Yanked off the cam pump. Cams look good. Cams lobes look like they are in good shape. All of the lifters and cage look in good shape. After I removed the lifter cage I found some swarf either left over from the machining process or something got buggered from the last person in there. Got the head off. The bores looked ok. No scoring and no D-Chunking. 4-6 Head looks good on the surface. Looks like I can take both heads to the machine shop to be cleaned and tested. All done for today. I plan to tear apart the short block in a week or two when I have time. My helper and I now have to clean up the mess in the garage.
At first glance it did not look like it had an intermix issue but as I dug in deeper I could tell that there was a small amount of coolant in the oil. Most likely from the beginnings of the d-chunking on cylinder #1
I bet there is a crack in the head on the shiny cylinder. Get it in good light and look real hard. It will show up if you send it to a good shop even if you don’t see it. Pistons that are steam cleaned are good evidence of water in the cylinder.
03-16-2019, 11:29 PM
Digging into a cheap 996 core motor.
