It has never been in question that 70s and 80s BMWs are good quality vehicles, but with pressures and requirements of modern motoring, coupled to the spiralling costs of fuel, many Neo-classic BMW owners search for improvements – not only in overall performance, but also in drivability and economy. In the last 10 years, we at Fritz have been searching the range of BMW engines and transmissions in a quest to give our customers the improvements that they desire, whilst retaining the cosmetic ‘retro’ look that the earlier models offer in abundance. Here are some of our favourites, as well as the Pros and Cons of taking on such modifications.

M42 B18

The eager and surprisingly tuneable 4 cylinder 16 valve unit from the E30 318is, E36 318is and E36 318Ti Compact has been a favourite of ours for years. The compact design lends itself perfectly to replacing BMW’s 8 valve M10 and M40 engines, in pretty much all their applications, but of course there are always pit-falls to consider.

M42 into E10 (2002) RHD

In short, this conversion is fantastic and produces a phenomenal result in terms of performance and economy – but represents a huge amount of work, due to the other systems on the car that require modification, in order for the engine to fit and operate in the engine bay.

Pros
Vehicle retains original weight distribution.
Economy in excess of 40mpg.
Out-performs even the best 2002Tii.
Large improvements in reliability.

Cons
Modifications necessary to :-
Steering Column
Clutch actuation
Front cross member
Battery location
Steering geometry
Steering method – From box to rack.
Cooling system
Engine breather system
Engine mounts
Prop shaft
Exhaust
Fuel delivery system
Speedometer and instruments
Vehicle electrical system.

 Difficulty level – 9/10

 – M42 into E21 316, 320, 323i RHD

Another great home for an M42 engine, and a fair bit easier than getting it into a 2002. Once again big improvements in performance and economy versus the original M10 and M20 engines, whilst retaining the crisp handling associated with these models.

Pros
Vehicle weight distribution retained or improved over the 6 cylinder models
Fuel economy in excess of 40mpg possible
Improvements in reliability and servicing costs
Faster and more agile than a 323i

 Cons
Modifications to:-
Battery location
Engine mounts
Exhaust Fuel delivery system (316 and 320 models)
Cooling system
Vehicle electrical systems
No PAS available with this conversion.

Difficulty Level – 6/10

– M42 into E30 M10 and M40 models

Not really sure much needs to be said about this conversion, after all BMW produced a 318is E30. Some earlier E30 models will require a little bit of attention in terms of cross member compatibility and radiator mountings. With this in mind, and the fact that the carburettor inducted models will need a change of fuel delivery system, there really are very few drawbacks to this conversion.

Pros
Faster, more reliable – everything else you can possibly think of!!

Con
You will need, at the very least to upgrade the exhaust system.

 Difficulty level – 2/10

M42 – Notes

The conversions we have discussed in this section, were all achieved using the E30 version of the M42 engine, which has the correct sump profile, and as far as UK versions are concerned, no necessity for Lambda sensors to be fitted. If you are starting off with the later E36 version, be prepared for the purchase of an E30 sump set and oil pick up before you start getting the spanners out.The only real weak point of the M42 engine is the way it reacts to high coolant temperatures. Get it hot, and 8 times out of 10, you will crack the cylinder head, which is getting an expensive item to replace. Whenever you acquire an M42 engine, whether in a car or as a unit, ALWAYS replace the water pump, thermostat and radiator as a matter of course, and always insist on a water pump with a steel impeller – do not under any circumstances use the water pump with a plastic impeller.

M50 / M50 TU B25

First of BMW’s new generation of 6 cylinder engines arrived in 1991 across Europe, and has proved to be one of the most reliable and forgiving power plants they have ever produced. We at Fritz see very few faults with any of the M50 range – the odd head gasket failure and cam chain stretch on more abused, high mileage units. The M50TU requires a little bit more care when servicing, due to the VANOS filter, that must be replaced at every oil change. If you decide to use one of these engines for a conversion, please don’t forget that it weighs 20kg more than the proceeding M20 engine, so in some cases, it is wise to consider possible front suspension and brake upgrades to your vehicle.

– M50 / M50TU into E21 320/323i

This conversion is a pretty good all-round solution to the E21’s 6 cylinder woes. Lets face it, the E21 320 M20 is very disappointing and the 323i suffers due to its pitiful K-Jetronic injection system – where the fuel goes is anybody’s guess. Due to the restriction of high differential ratios available to the E21, we at Fritz opt to use the original E215 speed overdrive manual gearbox, which as a result, requires the engine to be ‘stood up’ slightly from the normal angle of slant found in most E36 and E34 model.

Pros
230-240bhp output possible
35mpg + possible
Ability to annoy pretty much everybody off the traffic lights
Fairly easy installation

Cons
M50/M50TU engine 20kg heavier than original M20 engine
Modifications to :-
Cooling system
Suspension and brakes on some models
Differential ratio and fuel system on some models
Sump and Oil pick up

Full custom exhaust required to get maximum benefit from the conversion.

Difficulty level – 6/10

– M50/M50TU into E30

This is probably our most popular engine conversion, pretty much all the necessary components are original equipment parts, and everything slots together nicely, giving a fantastic overall result. Possibly what the E30 325i Sport should have been in the first place.

Pros
230-240bhp power output with minor tuning
35mpg + fuel economy
Bullet-proof reliability
Very few modifications necessary to vehicle system

Cons
Smaller brake servo necessary
Electric coolant fan conversion
Weight distribution effected
Will require a higher differential ratio than standard E30 models
Will require custom exhaust system to gain maximum benefit

Difficulty level – 4/10

S50 B30 + B32

Based on the M50 range of engines, these high output 3 Litre and 3.2 Litre units were found in the E36 M3 and M3 Evo cars during the 1990s. The engines are of extremely good quality on the whole, but do require regular, proper servicing, otherwise you can be looking at some very expensive repair bills. The 3.2 Evo engine in particular is very highly strung, with its 100bhp/litre output, missing service intervals and using non-original equipment parts is definitely a no-no.The main issues we see are failing VANOS units – due to poor servicing, and damaged big-end bearings on cylinders 5 and 6 – due to faulty oil pressure release valves and tired oil pumps. As these engines rev to a high level to produce their peak power, no compromises can be allowed with the upkeep of these engines.

S50 B30 + B32 into E30

For those of you out there who think you have mastered driving an E30 fast, these conversions will certainly sort the men out from the boys. With outputs in excess of 300bhp and engine masses exceeding 150kg, the S50 conversion pushes the E30 body shell and chassis design to the limits. Fitment of such engines, in the main, are similar in procedures necessary to fit an M50 B25, although due to the S50’s enormous induction plenum chamber and marginally more complicated electronics and EWS system, the installation takes longer and is more expensive. With the installation of such power units, it becomes very necessary to consider all aspects of the vehicle you are fitting it to – Suspension, brakes and final drive gearing will all need replacement and/or upgrade to cope with the extra power and to keep you and your car out of the scenery.

Pros
Unbelievable performance
35mpg + fuel economy with correct gearing
Scare super car owners on a daily basis

Cons
S50 engines are expensive to buy
S50 engines are expensive to maintain
Weight distribution compromised by large engine mass
Every major systems on the vehicle will need to be upgraded
Complicated installation of injection system and EWS
Full custom exhaust necessary

Difficulty – 7/10