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!

Hobbes
Hobbes
1/8/19 9:50 p.m.

FYI for anyone interested, the red one is for sale if you're willing to spend the dough...

https://raleigh.craigslist.org/cto/d/youngsville-1991-bmw-318is-coupe/6780041200.html

GTwannaB
GTwannaB HalfDork
1/9/19 9:45 p.m.

So what is the price tag for building a similar stroker motor to this?

Tim Suddard
Tim Suddard Publisher
1/10/19 8:11 a.m.

All in, it is about $7500 to build this engine. And while that might sound a little steep, everyone who has driven the car so far has said that at that price, it is a bargain, as this is a very, very sweet E30 and when we run it against an M3, i have no doubt it will not only fare well, but embarrass it.

Ian F
Ian F MegaDork
1/10/19 8:21 a.m.

What are the advantages to rebuilding a M42 like this vs doing some upgrades to a M44?

With the price of E30 M3's, something like this does seem like a good way to get a car that performs like an M3 at less cost, if not "cheap".

z31maniac
z31maniac MegaDork
1/10/19 9:24 a.m.
Tim Suddard said:

All in, it is about $7500 to build this engine. And while that might sound a little steep, everyone who has driven the car so far has said that at that price, it is a bargain, as this is a very, very sweet E30 and when we run it against an M3, i have no doubt it will not only fare well, but embarrass it.

Heady praise!

I can't wait to see perhaps a better intake, header, injectors, Megasquirt and E85. I suspect that would it have it up near 200 at the crank.

2002maniac
2002maniac Dork
1/10/19 10:15 a.m.

I have driven many E30s in varying configurations and can attest, a 318is with a 1.9L 11.5:1 build (stock crank, max bore) pulls noticeably harder than a stock M3.

Also, if anyone wants to build a more budget friendly 2.0 M42, here's my recipe:

  • M44 crank
  • 140mm M42 rods
  • S52 pistons with 1.5mm decked off the top and valve reliefs recut (I was a machinist at the time, so why not)

According to my calcs this should have resulted in a 2.0L displacement and ~11:1 compression.  Unfortunately I built the bottom end just before my car was totalled, and I have never had the chance to put it in anything else.

captainawesome
captainawesome Reader
1/10/19 12:37 p.m.
2002maniac said:

I have driven many E30s in varying configurations and can attest, a 318is with a 1.9L 11.5:1 build (stock crank, max bore) pulls noticeably harder than a stock M3.

Also, if anyone wants to build a more budget friendly 2.0 M42, here's my recipe:

  • M44 crank
  • 140mm M42 rods
  • S52 pistons with 1.5mm decked off the top and valve reliefs recut (I was a machinist at the time, so why not)

According to my calcs this should have resulted in a 2.0L displacement and ~11:1 compression.  Unfortunately I built the bottom end just before my car was totalled, and I have never had the chance to put it in anything else.

This sounds like something I'm interested in for both my m42s. Finding a machinist that will touch or machine pistons locally like I would need ends up being the biggest issue though. If there's an off the shelf piston option to combine with the m44 crank and m42 rods for a similar setup I'm all ears. If it's a few hundred more for that I'm cool with it.

ErikTheSwede
ErikTheSwede New Reader
1/11/19 8:48 p.m.

Just put a Toyota 3SGE BEAMS engine in it and be done

captainawesome
captainawesome Reader
1/11/19 9:03 p.m.

In reply to ErikTheSwede :

As cool as that sounds, the exhaust and intake are on the wrong side making the swap difficult. Tuning can be pretty tough with them as well. Then the resale value of a 318is with a Toyota motor would be laughable. A nice 318is can fetch 8k and up these days.

ErikTheSwede
ErikTheSwede New Reader
1/12/19 6:04 p.m.
captainawesome said:

In reply to ErikTheSwede :

As cool as that sounds, the exhaust and intake are on the wrong side making the swap difficult. Tuning can be pretty tough with them as well. Then the resale value of a 318is with a Toyota motor would be laughable. A nice 318is can fetch 8k and up these days.

I know. I'm just running my trap. I genuinely hate BMW engines but love their chassis and suspension. I am guilty of looking at more than 1 E36 318TI and having visions of the 9000 rpm Toyota 4 cylinder swapped in there

GTwannaB
GTwannaB HalfDork
1/12/19 9:29 p.m.

I have to say this motor in an E36 is what interests me. I can pick up E36 for $2500 all day. They don’t have the E30 tax. But they do have, what a 200 - 300 lbs penalty over an E30?

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