The current 265hp/260lbft engine is still in the car, and I wanted to keep that complete, as it has no issues and will make a good spare if all else fails. In light of this, I dropped on lucky with an extremely cheap M54B30 engine, which gave me another set of crank/pistons/rods. I already had a spare iron block, but I was short of various other bits like cylinder head, sump, covers, etc. A short while after, I picked up a cheap complete 328 engine and gearbox - which worked well as I wanted to swap my box anyway (leaks slightly) and again the price was cheap.
I stripped the 328 engine apart, then got the bare head and spare block to the machine shop to be checked before doing anything else. The block checked out, as did the head. I wanted to get as much off the block as possible this time, and use a stock thickness head gasket - yet taking into account the timing chain, valve clearance, etc. I knew this block had already been decked once, and either way it was done again after I had double/triple checked clearances. Bores were honed and cylinder head skimmed.
Once I had the block and head back, I set about cleaning up the 3.0 parts, more so the piston ring lands, as its obviously not a great idea to fit brand new piston rings in grooves that are full of baked old oil. I always cringe when I see people use a broken piston ring on an aluminium piston to scrape the oil out, as they are so easily marked/damaged, and I didn't want to make any change to the dimensions of the ring lands AT ALL. The carbon was pretty well baked on deep in the grooves..
After plenty of research, I didn't want to have to sit there with a nylon/plastic brush and use chemicals to dissolve the carbon (as most damage the aluminium anyway) for hours on end. The only alternative was media blasting - but the media needed to be safe with aluminium and not even make a mark. From this, I used my air gun, made a DIY siphon feed and used baking soda as the media. It took around 30 seconds per piston to get them spotless, ring lands included. Baking soda is completely water soluble, so a quick dip in a bucket and all the media is gone...
Also cleaned up the rods, to make a clean set ready to go..
With the block on the stand, the oil jets were dropped back in, then ARP main studs installed, and new bearing clearances checked. All well within spec. The crank was then cleaned again, caps fitted and torqued down.
Next I set about checking the new piston ring gaps for each cylinder, which were all within spec. Each set then went onto the respective piston, and into the block.
One all six were in the block, I checked the clearances on the new rod bearings. All checked out within spec, so ARP rod bolts were installed and torqued.
Stripped the oil pump apart to check and clean... all good. Installed on the block with a new chain.
Next on the list was the head. New stem seals, then quickly lapped in and fitted the 24 valves. Finished with a quick leak test.
24x 'N series' exhaust studs installed - silly not to at 0.30p each.
2x new chain guides, and new main chain installed.
2x new dowels and ARP head studs wound in. Both block and head cleaned, then gasket and head dropped on. Torqued down to spec, all good.
Before fitting the cams, I wanted to strip and clean all 24 hydraulic tappets like I did on the current engine. Time consuming, but worth knowing its done.
I originally looked at CatCam and Schrick, but both have very long lead times, and require either fixed timing (no VANOS) or aftermarket pistons. I wanted to keep the internal parts stock-ish, so eventually managed to source some S52 cams and matching trays from the USA. They need to be from the USA, the difference being their M3 engines were practically a modded 328 lump, completely different to Europe, so the cams drop straight in, and retain single VANOS. Spec wise, they are the same as the basic Schricks - as the S52 cams are hard to come by, they started to manufacture and sell the same profile.
With M52 (328) cams being 228deg/9mm on both inlet and exhaust, the S52's give a nice increase at 252deg/10.2mm on the inlet, and 240deg/9.7mm exhaust. The cleaned tappets were fitted into the trays, then both dropped into the head, torqued down and locked at TDC.
More to come...
