N52B30 Engine rebuild and head porting

[4JawChuck]

Since this 3.0L has forced the issue I am rebuilding its N52B30 engine back to essentially stock specs except for some minor porting/blending and mods such as headers.

Since it’s going to be a daily driver I just wanted to address the easy low hanging fruit issues I’ve found with the engine and what was done to mitigate them without destroying driveability and/or mileage during the daily commute.

The engine crank bearings bit the crank during cold starts here in Canada, seems to be a common theme as I have seen a number of these engine seized with vehicles for sale as a result. Seems the tin/aluminum bearings don’t work well in the colder temps and/or poor factory tolerancing or design. Not going into why BMW has an issue with all their engines having bearings failing…just want to fix it so it doesn’t happen again and also bullet proof the engine so I can rely on it.

I’ll post a couple pics showing the damage and where I am in various stages of the build.

[4JawChuck]

More great news, I’ve decided to strap and stud the mains instead of replacing the bedplate/engine…there’s room under the windage tray for a 3/8” thick strap on top of the mains bolts.

Notice the only journal cap not cracked is the rear which was the one that bit the crank.

Sorry ignore the first photo, couldn’t figure out how to edit after the posting.

[4JawChuck]

Head porting pics, almost entirely exhaust stuff done except for the intake valve unshroud on the leading intake, not sure what this is going to do for idle quality but I could not leave it almost completely shrouded for the first 5mm of lift…it offends me and is likely more for emission control that anything else…we will see what needs to be done with a tune etc after it’s running.

[4JawChuck]

Final chamber look with clean valves.

[4JawChuck]

Pic of the finished painted head in AL silver, prepped the material with a Phospho rinse and scrub and then after baking black etching primer as a base.

The block is getting painted something close to aged DOW7 paint like you see on old magnesium engine cases.

Next is reassembly and valve lapping.

[MAMSport]

Are the main bearing caps cracked or the block sides (or both)? That is crazy! Head porting looks nice, but is it all smooth? One of the images shows tool marks, so I wasn't sure.

[4JawChuck]

The magnesium carrier for the cast-in ductile iron caps is cracked along all the caps except for the one that spun.

I’m making ductile caps to fit under the wind age tray, when tightened down and torqued the cracks were not visible. Studs will be added as well, still need to source ARP versions that aren’t torque to yield.

The tool marks are virtually non-existent. That’s a zoomed in photo that you see the marks in. Smoothness not really an issue inside a combustion chamber other than being a magnet for carbon buildup.

[4JawChuck]

Some bore cleanup pics taken while doing grey abrasive pad (600grit) honing and final polish with 1200 grit foam backed pads for the bore conditioning. I tried to take some close ups so you can see the silicon carbide inclusions in the aluminum matrix as well as some images of defects in the surface from carbon scraping between the piston and bore, originally these were black marks on the bores which didn’t catch a finger but were obviously occluded from holding any oil in its plateau.

The close up pics show the scrapes into the base metal but you can see it did not affect the silicon carbide “plateau” as they stayed intact and projecting about the base aluminum. For reference the cleanup photos show scratches on the bore edge and those were from pulling the 1200grit foam pad out along with the foam polishing pad so it’s microscopic in size. No AN30 paste was used for any of this procedure.

I’m calling this good, block has been deburred and just needs another wash with detergent and phosphoric acid cleaning to get ready for paint. 50/50 acid to water, just using metal prep which has a soap in it.

I’ll post up some block finished painting pics once it clean.

[4JawChuck]

Getting masked for paint then a wipe down with paint prep solvent and blow down for black self etching primer.

[4JawChuck]

Various stages of the paint job, flat black etch followed by gold wheel paint followed by a brownish bronze color. Was looking for an aged DOW7 color like old drag race mags made of magnesium.

Pretty close, hard to capture the Color with the LED lights in the garage. In natural light it’s much darker and the low lights in the corners that are gold shine through more, the passenger side facing the open side door shows more what it looks like in outdoor light hence why they look different from each side.

[4JawChuck]

Final mock-up to see how it looks with the AL silver head, black valve covers and black steel powder coated oil pan are stock so it should not be ostentatious.

I like it, what do you think?

[AKA]

I don't know why you're not getting any comments but I'm enjoying the show!!
I don't at all understand how the cracks are being repaired (bolting something on that holds them together? ) or why you wouldn't start what looks like a lot of work from a non-cracked junkyard engine.
But i'm looking forward to see this progress. Very cool.

[Olgeezer1]

Hugely impressed. Not many, me included, would have the knowledge / equipment to take on such a project. A hand built engine is a rare thing these days.

[4JawChuck]

I've been building engine for quite some time, aircraft radials and plenty of car stuff from mild to wild and some exotic and old...mostly for other people.

I didn't buy this car to rod, it's my daily driver and it's put me into a Fiat500 spare car that drains my soul.

In good conscience I could not just do a swap with a questionable motor from the yard especially when I seen the inside of this one which appeared mint minus the spun bearing.

That led to a tear down to see why...and if their is a cheaper way to do this. I've never had a BMW engine apart but I've done a few rotary engines back in the day and how hard could it possibly be. I've got three engine stands in the garage, sons 302 Ranger engine ready to go in and just a few motorcycle to move around so I could do this right.

The cracked cradle was a bummer for sure, however it's not something I haven't done before to save a block that was virtually priceless for some old pre-war beaut. I'm still engineering the final block caps and sourcing the right fasteners, part of me wants to put some grade 12 bolts in there and call it good but I know better regarding TTL and this needs to done properly to survive.

What's looks catastrophic to most is just a challenge to me, it's really the only weak point that I could point too and say...that needs more meat. I have some ductile cast material coming and dimensions but it really depends on what those bore measure out too after the initial phase (which could have pins or additional setscrews to add stiffness. I can make my own parts and have access to specialized equipment to make it happen.

My theory though is there must be many of these blocks like this out there, you couldn't see any cracks when the mains were tight, those cracks completely close up and are invisible. The cast in ductile insert inmbedded in the magnesium is keyed in a hardened insert of AL on the top so the gussets are only for lateral stiffness near the edge of the block where the center is mostly filler material. I've thought of cross bolting as there is material there and honestly a cap for studs would prevent that block from ringing especially if I dowel the two together around the hole.

Many ways to skin the cat, still figuring that out as I go along and take measurements of the mains bores after applying the strengthening cap.

P.S. since having the head on the bench and porting the lip from around the leading intake valve I have a theory on why the MILV mod works on these cars so well, your basically lifting the valve high enough out of that shroud so the valve can flow where there was nothing before hence the across the board power increase. Just a theory.

[4JawChuck]

Just some pictures of the completed head assembly ready to install and time, new headers to be ceramic coated (Roundel Works), one inch longer grade 12.9 bolts for the mains to replace the TTY 10.9 BMW versions for the bridge to be fabricated on the center mains on the bed plate.

Pipes are very well made with excellent welds, heavy duty flanges plus reasonable in price compared to others I’ve looked at.

[4JawChuck]

Slow uploads, had to redo.

[WrathOTM]

What is that fancy looking tool in the last pic? Looks amazing so far.

[SKI-R]

MILVs install tool.

[4JawChuck]

Yep, allows you to compress the hairsprings on the valvetronic linkages which pretensions the lever arms against the intake cam.

Fancy tool that you need to remove and install these springs safely…for a total of 15mins of usage. I disassembled the head without it and that was dangerous. Absolutely need it to reinstall.

[4JawChuck]

Did a mock-up to check clearances on the mains and rod journals and found the mains tight at 0.0018” clearance and about the same on the rods.

What concerns me is the main journals are 2.200” in diameter which gives less than 0.001” clearance per inch of diameter which is a standard bearing clearance as a rule. My engine machinist had micro polished the crank to remove 0.0005” for additional clearance which I asked for. So the factory mains clearance on the mains was closer to 0.001” total, which is very tight even for a low rpm motor.

Took some images of the new King and ACL bearings so people can see what they look like, the King main bearings are the newer silver back style and the ACLs rod bearings are just coated trimetal bearings which should be fine for the rods as plain trimetal original replacements were fine when they were inspected at tear down.

Have not fabricated the girdle yet but wanted to make sure the cracked bed plate did not warp the main bores, plastigauge on multiple points on the journal showed them to be round which is good, obviously the cracks are superficial to the main cap diameter and just indicate poor bonding to the ductile cap inserts.

Disappointing to say the least to have such an obvious mistake made in clearance selection from the factory for the mains, way too tight at 0.0013 clearance.

Last two photos show damage to the register on the rear main where the bearing almost spun which brinelled the register slightly, this was peened to raise material and then filed back to have a solid register for the bearing tang to sit solidly. If this area is badly damaged it can wreck the block for rebuild, luckily this one wasn’t that bad.

[WrathOTM]

Hope this build comes together for ya. Wish I understood engine clearances better.

[4JawChuck]

General rule for any plain journal bearing is 0.001” for each inch of bearing diameter, measured clearance of the stock journals and bearings showed clearances half that.

Performance engines are usually afforded additional clearance of 2 tenths or 0.0002” per inch of diameter additional clearance due to heavier loads, in this case a “performance clearance” for this engine would be 0.0025” but even after aggressive polishing I could not achieve that additional clearance, if I was racing this car I would have to regrind the crank and run smaller rebuild bearings to get even close to this which would remove the laser heat treatment given to the journals on these BMW crankshafts.

Just food for thought for those looking to extract more from these engines, I would not trust it to make high rpm with stock bearings and clearances…recipe for disaster.