The E30 Upgrade Engine Guide

Trying to figure what the next step is for your e30? Here is a quick guide to the popular engine swaps you can do to add a little more fun to your Bavarian brick. From mild to wild, there are plenty of ways to make your e30 anything from zippy to outright dangerous...be sure to install some grippy tires!

M20B25

This is the motor that came in all 325i, 325is, and 325ix models. It is a 2.5-liter single overhead cam inline six. Overall fun little motor if you like it for what it is but you won’t be making big powa with just a chip or a cam.

M20B27

If your car is a 325 or 325e it has a lower horsepower version of an m20 and some people upgrade to the b25 motor. The 1988 “super eta” models are great candidates to swap the top end from a 325i, creating the 2.7i “budget” stroker.

Pros:

Keep it original
Reliable if you maintain it and fix some of the basic known issues.
More than enough power to get out of its own way.

Cons:

Interference motor with a timing belt. Which means, if the belt snaps then the motor will be toast.
V-belt driven accessories
Requires periodic valve adjustments
Rocker arms require upgrading for sustained higher RPM applications

M20 Upgrades:

Stroker m20

The “hot rod” approach to building an m20 engine. Depending on the crankshaft and piston configuration, stroker m20 displacement generally ranges from 2.7 to upwards of 3 liters. For best results, stroker engines benefit from a performance cylinder head and exhaust system. Standalone engine management may provide additional power gains when professionally tuned.

Pros:

Getting the most out of the m20
Looks factory
Retains original e30 character with added performance

Cons:

Requires engine rebuild for best results
Producing over 200 horsepower can become very expensive
May compromise passing emissions and day to day street manners

Turbo

The best type of creep is boost creep. There are a few kits out there to boost your m20 to the moon and back. One popular one is by KA motorsports out of Nevada. But the pros and cons are applicable to any turbo setup.

In most builds a stock m20(with freshened stock internals) it can easily make upwards of 250 whp without issue. 300-350whp on stock internals is commonly regarded as "reliable." Around 425wtq is the generally accepted limit of stock internals (rods) but people push past that and just accept it as a ticking bomb.

Pros:

That boost power curve
Popular way to produce high power figures
The turbo “Cool” factor, it makes all the right noises to make car people go “Oh, why hello there”

Cons:

Kits are usually not 100% complete. You will most likely have add your own accessories
Converting engine to accept boost can become costly, especially if using quality components
Custom tuning required for each individual application. tuning standalone ECU to be comfortable, easy to drive, etc. is a lot of work. Not knowing what you're doing can result in blowing up your motor.
Likely to cause reliability issues and identify weak links within drivetrain
Hard to live with as a daily driver

M42

This motor came in 318is. It is a 4 cylinder dual overhead cam. It was the most technologically advanced motor put in an e30 from the factory.

Pros:

Keep it original
Light curb weight of just over 2600 lbs
Timing chain
You can call your car a baby m3 (please don’t)
Easy to work on

Cons:

Extra slow
The timing chain sprocket and chain guides known to fail, can cause serious engine damage
Timing system rebuild is rather expensive
Valve cover bolts may strip heads in cylinder head if not careful
Factory main bearing oiling system is not ideal for high RPMs
There is a rats nest of lies under the manifold
You have people calling your car the ‘baby m3”

The Swaps

M30

The “big six” is the engine as found in the 5, 6, and 7 Series BMWs of the 70s, 80s, and early 90s. The m30 is a torquey motor that is a great way to add some low end grunt to your e30 without too much complexity. For the e30, the later B35 variants are the most popular as they are the most powerful of the bunch and run off the same style engine management as the late model e30 m20 cars.

Pros:

Mechanically similar to an m20 style engine
Plenty of low end torque
Relatively affordable engine and transmission package
The period correct swap
Likes boost
Probably the easiest swap to make California legal

Cons:

Mechanically similar to an m20 style engine, such as the valve train meaning that you would still have to do valve adjustments.
Old technology
Poor gas mileage
Physically long engine that sits close to radiator
Not as readily available in junk yards anymore

M50/M52

Arguably the most common engine swap into an e30. Sourced from an e34 or an e36, the M50 & M52 provides the extra bump in power that many feel the e30 should have had from the get go. Not terribly exotic, the M50 and M52 engines are solid workhorses.

Pros:

Runs and drives like a much newer car, The throttle more responsive, engine smoother with a wider powerband.
Easier to maintain
A well documented swap that is very well thought out at this point
Improved engine management
Better MPG

Cons:

A fair amount of work for moderate power gains
Likely high mileage motor that needs refresh
Harder to find a cheap one these days
Cooling system generally requires electric fan for better radiator clearance

S50/S52

Based on the M50 engine family, the S50 and S52 are the factory performance variants found in the e36 M3 and Z3 M cars. Plenty powerful for the lighter e30 chassis, the S50 and S52 are a great way to reliably add significant performance to your e30.

Pros:

Similar to M50/M52 in terms of swap requirements
Plenty of power in stock form (has the horsepower as the most powerful road going factory e30.)
Not an exotic M car engine, so reasonably available and easy to maintain

Cons:

Same cooling fan real estate issues as M50/M52
Older engine that likely has high mileage and requires refresh
Higher initial cost over an M50/M52 engine conversion
May overwhelm stock brakes and suspension if you are looking to autocross or track the car.

S54:

The M50 engine on steroids! Individual throttle bodies and 8,000 RPM of motorsport melody. Taking the DOHC inline six to the absolute limits, the S54 is the traditional BMW recipe perfected.

Pros:

Over 300 horsepower out of a Naturally Aspirated engine.
Keeping it in the BMW family.
Very well documented at this point.
Definitely has the “cool” factor.
One of the most modern motors on the list.
OBDII: allows for easier tuning, and troubleshooting

Cons:

Can be a very complicated swap
Expensive
The motor will need to be gone through before it is swapped in, the s54 is known to eat rod bearings.
Will need to adjust valves unlike the m50 or s52
Very difficult to get CA smog legal

The V8 Swaps

All the v8 swaps into e30s have one major flaw, the braking system. The motor being so wide that the brake booster has to be moved or removed. Which adds a whole nother level of complexity to the swap. It can also greatly change the braking performance of the e30

M60/ M62

These v8s are found in mid 90s to 2000s era bmw 540 and 740s the m60 is a 4 liter while the m62 is a 4.4 liter. They have the same basic 32 valve redesign. The m60 has around 280 horsepower in stock form.

Pros:

Keeping it in the bmw family.
All the V8 noises and low end torque
Cheap motor to buy.
They usually come with 6 speed transmissions.
Good power level for a hotrod e30 while still being able to hit the backroads. Anywhere from 280 horsepower on up.

Cons:

A very wide motor because of it having dual overhead cams. Which can make it a very tight fit.
M62s can eat timing chain guides and vanos should be refreshed before the engine is swapped in.
Either have to modify the oil pan or use subframe spacers which change the suspension geometry.
Not much after market support

The LS family.... dun dun dun

The LS swap is a love it or hate it thing. The come from almost anything with a gm badge. There are a few kits out there to fit it in to an e30. You can build anything from the cheap and cheery junkyard swap to the full race built ls7.

Pros:

Simple
Plentiful
Can get parts at the local auto parts store
Reliable
Bolt on performance parts can make a ton of power.

Cons:

Even a “cheap” swap can add up very quickly.
Have to deal with hearing “another LS swap.”
Will be very hard to make it smog legal in California.

The E30 Upgrade Engine Guide

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M42

The Swaps

﻿M30

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M50/M52

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S50/S52

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S54:

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The V8 Swaps

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The shade tree swap. California legal lS3 e36 318ish - Part 1.

The “i”- The E30 I Should Have Never Bought

M30