Oct 18, 2018 update to the BMW 318is project car

Project BMW 318is: Building A Stroker

While we had the engine out of our 318is, we decided to take the opportunity to rebuild it for more power and torque–because more is always better, right? And there’s still no replacement for displacement. Like our earlier engine work, these modifications were done at Metric Mechanic, where owner Jim Rowe and his gang have figured out a way to build a relatively inexpensive, yet rather trick, 2.0-liter engine out of our car’s stock 1.8 liter. By combining elements of our car’s original M42 engine with parts from BMW’s later M44 engine–the same one we stole the lower timing chain cover from–Rowe and crew created a stroker for us. Their formula uses the unmodified crank from the 2.0-liter M44, some custom, short-skirt pistons they have designed, and the 318is’s M42 engine block with some additional boring.

M44 Crank

The M44 crank (left) is significantly different from the one from our earlier engine. Most noticeable is the crank sensor wheel on the back of the M44 crank. Although our stroker engine won’t need this crank sensor’s inputs, it will need the balancing provided by this wheel. (Similar six-cylinder engines also used the crank sensor, but with no balancing component.)

MM Rods

The engine builders at Metric Mechanic believe that a lightweight rotating assembly is the answer to all things performance. Keeping weight down will increase the engine’s ability to rev, will reduce the amount of heat it produces, and will reduce wear and tear on the engine. They drop that weight by using their custom I-beam connecting rods (at right) with lightened wrist pins and ARP fasteners to replace the stock pieces (on the left).

Rod Bearings

More pro tips: Metric Mechanic uses rod bearings (left) that have an oiling groove around the entire bearing, rather than just halfway around the bearing as on the original engine.

Rod End Cap

The rod end cap needs to be modified slightly to accept the tangs from the new bearings.

Pistons

Our new, larger 87mm pistons are custom made for Metric Mechanic with shorter skirts to work with the 2.0 liter’s increased stroke. They are also lighter than stock and coated for less wear and more durability. Ours were balanced to even up rotating mass.

Piston Valve Grooves

Another trick: Metric Mechanic cuts more clearance in the pistons for the valves, making the engine much less prone to damage if the timing chain fails. The indentations in the pistons also provide a bit of room to deck the block.

Water Outlet Piping

The stock water outlet piping is pressed into the head and tends to rot away, so Metric Mechanic replaces it with threaded pipe of the same diameter that can easily be serviced.

Block

The block is cleaned, bored, honed, checked for straightness, cleaned again and then painted in traditional BMW black. Here, modifications also have been made to improve the water passages and mount a windage tray.

Thrust Washer

The third main bearing serves as a thrust washer on the M42 engine, so before going any further, the technicians check end float to make sure the thrust washer is doing its job correctly.

Pistons and Rods Installation

Piston and rod assemblies are tapped into place with two special tools. The ring compressor that Tyler Davis is holding in his left hand is specially made to assemble engines with 87mm pistons, while that is a plastic–not metal–device in his right hand was built to gently tap pistons into place.

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Comments
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wheelsmithy
wheelsmithy SuperDork
10/18/18 6:16 p.m.

Yep, awesome!

This is the internet, so, I'll pick at details in a good natured way, this time.

Wouldn't you call the new con-rods H-beam, compared to the old I-beam? Maybe I'm confused.

This is a sweet build.

captainawesome
captainawesome New Reader
10/19/18 8:29 a.m.

What kind of power potential does this all translate to? I've been considering going this route VS the m47 crank.

Tim Suddard
Tim Suddard Publisher
10/20/18 7:21 a.m.

wheelsmithy,

 

I do not consider myself an engine builder, although I have built an engine or two. I'll ask Jim Rowe, but this is what he called these connecting rods

 

And Captainawesome, the builder said I could expect 160-170 hp, but that is with the restrictive stock fuel injection with only a chip and larger injectors changed. With a stand-alone FI system,  there may be even more horsepower available.

I think I am going to be happy with the simplicity and reliability of the stock stuff for now!

DocV
DocV Reader
10/21/18 5:31 p.m.

awesome!  I hope Metric Mechanic is still doing this when my M42 eventually wears out....

wheelsmithy
wheelsmithy SuperDork
10/21/18 5:47 p.m.

Tom, 

   I was being that nit-picking guy on the internet. Not important. I love this, and all the builds. Carry on in good health.blush

RickInABox
RickInABox
11/1/18 6:43 p.m.

Looking good! You all should put that supercharged 318i article back up so we can compare!

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