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Old 03-30-2015, 10:09 AM
Deansbimmer Deansbimmer is offline
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Location: Texas
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I have a parts washer at home so as I disassemble the "new" engine to clean everything, I pull the pistons and rods to survey the damage to the cylinders. Technically, in knowing that the blocks are Alusil, I only expect damaged rings, and that's what I find. Two pots will need to be re-ringed. I order the parts.

I also decide to forego pulling the crank for new main bearings, and instead just install new rod bearings. With the block bare and mounted on a stand, I clean the crap out of the block with a case of Berrymans spray.

The car sits in my driveway for a month like this:


I neglected to get a picture of the bare cleaned block, but this is a shot of the block without pistons after the bore reconditioning.


The bore's were stained (oxidized) where the standing water reacted with the aluminum, but that doesn't affect the bore's ability to seal. There is a lot of voodoo an unknown about these Alusil blocks, but let me affirm that these can indeed be re-ringed with no problem, and are even DIY friendly. Porsche aircooled guys know this too as they have the same Alusil cylinders.

I had ordered two new sets of Goetze OEM rings (the original rings I pulled were labeled Goetze too). I had cleaned all the pistons and bagged them, so after checking end gap (note the wall stain) and with new rings installed I bagged the last two also, before I started to rehone the block.




I used Sunnen AN-30 honing compound, specifically made for Alusil blocks. These blocks are not sleeved, coated, or anything tricky. The block has a high silicon content which is crucial for the bore's survival as the silicon (high hardness level) is an excellent wear surface.

Using this with felt pads around a standard spring hone and hand drill removes a slight amount of aluminum from the bores, exposing the silica crystal component of the Alusil block. The pistons/rings ride on the silica as they are more exposed than the aluminum. When you run your fingernail across the surface of the prepared bore, it feels almost like running across a chalkboard- you're skimming across the silica crystals. This is also great for oil retention as the bore is almost porous on a microscopic level.



Prepared bores:




Using a straight edge I found the block deck to be slightly cupped (low spots between the bores) which would cause a short life of the head gaskets, so I leveled the block using my at-home method which has served me well. MLS head gaskets are finicky and demanding of a good surface finish RA.




I continue to the Rod bearings. Using a micrometer and pastiguage I found the crank's rod bearing journals were within standard size bearing tolerance so I ordered a set of bearings and installed them with new torque-to-yield bolts. I soaked the pistons in oil and popped everything in with assembly lube on the bearings.



With a new valley pan, the bottom end is coming along nicely...




Ready for gaskets. Genuine BMW HG. They just seem to last...




I move my attention to the heads, which needed lots of love. I fully disassemble them, clean each part, and lap each valve. The surfaces weren't in spec either, so I level them out.... All better now.


New stem seals


Reassembled and ready for cams and installation.




Torqued them down and did the additional degrees...









Installed cams and loosely installed rebuilt VANOS. I used a Beisan seal and press kit to rebuild them so they'll last for another 100k.





Found true TDC and locked the cams for timing...



New genuine BMW guides and tensioners.


New front case seals, installed and set up. Cams timed, sensor wheels aligned in their jigs.


Buttoned up the bottom end, installed oil pump, locked down oil pump nut...




All together with new seals everywhere. New OEM seals on the axle shaft housings and differential too.




Getting ready for the intake...New knock sensors and valley cover.


Newly sealed diff, new pipes and hoses...


New alternator...Adding the accessories... Getting close!


Next morning... In she goes!






It was a late Friday night when I got it all buttoned up, fluids in, double and triple checked everything... I wanted to fire it up before going to bed so I could know whether to have good dreams or nightmares. Primed the fuel system and she fired right up. Real noisy at first...Then the oil system caught up and it settled into a good idle. She smoked a lot though from the tail pipe. I said I had a good days work and went to sleep with good dreams.

Next morning started right up, bled the coolant, checked for leaks, and went around the block to seat the rings. Did the "drive hard" method for ring seating. Smoked like a freight train for a mile then it settled down and ran like normal. Car runs and drives great. Fantastic smooth idle. Now to fix the rest of the bugs in the car....
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