Building M50b25tu NA high HP

So as some of you know, I happen to own two almost identical BMW E36 325i coupe´s. My plan for them is to have other one as a boosted and widebodied and the one on this post will be kept looking pretty stockish with aim to get as much horsepower and rpm out of the m50b25tu engine as possible.

Thus far I have mostly focused on doing maintenance on basic things an old car needs, like bearings, bushings etc. Next up the focus will go to suspension related things as of chassis stiffening, braces and better control arms. These will be covered in their own posts.

About the engine, as wanting to keep it naturally aspirated. I´ll need to get more air and fuel in to the cylinders to make more power, but only with vacuum pressure, as comparing to boosted application where you would have boost pressure giving more air volume.

Engine will get bespoke 50mm individual throttle bodies, with runner lengths matched and calculated to best performance at higher rpms. Cylinder head is the key to making more horse power in a NA engine, without stroking the engine out to bigger displacement.

My target numbers for the engine are to get around 250-300 hp and to get it to rev up to 9500 rpm, 10k rpm would be top notch but have to see about it. Exhaust will be also bespoke 6 to 1 collector and after either 3" or 3,5" exhaust with provision for electric cut out at the collector. Final exhaust manifold will be made out of most likely RST tubing, titanium or inconel could be at the future, but there aren´t any performance gains except weight from smaller tubing wall thickness. Manifold will be made to be equal length and have proper pulsing for the engine to evacuate each cylinders burnt gasses properly and help to draw in new fresh mixture with valves over lapping.

So my plan for the cylinder head is to do a porting job on it with also matching intake and exhaust flanges to the head. Exhaust side will most likely be just ported and polished, intake side will hopefully get port and poslishing with some other flow aiding mods. New bronze valve guides for exhaust will be installed with intake getting manganese bronze guides. Exhaust valves will be changed to inconel over sized valves and intake will be oversize black nitrile valves. Valve springs with their hardware will be changed to Supertech´s dual springs, with titanium hardware. Mechanical lifters will be fitted to support both dual springs and Enem camshafts.

Large variety of ceramic coatings will be applied to different surfaces of the head and the block to help the engine to lose less energy to heat, and create less friction between moving parts.

Engine block will have griddle plate fitted to support higher rpms, heavy duty oil pump to not to break the oem oil pump shaft. Rotating assembly will get new forged pistons and rods, which will be weight matched to have the least amount of vibrations together. All the mounting hardware will be changed to ARP. Bearings will be King´s racing coated bearings, which have polymer coating on them to aid with friction and oiling. Dry sump is not in the scope for this car at the moment but we will see later on the line as we get going if it is going to be needed. Also will be fitting ATI super damper, and undersized pulley kit, to free up some horse power in that area.

Will be posting more detailed articles on all the mods, when they become relevant.