The 24 Hours of Lemons Forums → Lemons Tech → E21 engine conversion
Looking at buying an e21 that is blown up for dirt cheap. Wondering what engine would be good to replace the old 1.8l that was in it? I'm thinking on an m50 or maybe even s50 if possible. Any of these engines reliable or any other suggestions? Thinking on getting the zf 5 speed out of the 1990-2000 3 series since it holds up better than getrag tenants.
What is most plentiful in your local boneyard? I would lean that way or c-list cars. M52 make good power and are plentiful these days but a simple M10 makes good power for an E21.
M30B35. "Senior Six" Found in e34 and e32 535i's and 735i's. 208hp/222tq,
Running, lower mileage examples available all day from dismantlers for $300, bulletproof workhorse SOHC of an engine. Won't get you penalty laps like an M3 engine will.
In order to go to a 6-cylinder with a simple swap in, you'd need a different front subframe out of Euro E21 323i (or many hours of fab work). My e21 has seen over 15 races with an M10 and personally I wouldn't go to a 6-cyl engine due to higher front end weight, much higher fuel consumption, tire wear, brake wear... And speaking of being bullet proof: the M10 is on par with any other reliable engine.
Now, where you gain power is dumping the mechanical fuel injection system for something different: an old Weber with the intake manifold from a 2002 (bolt on, but need to change a fuel pump form high pressure to low pressure one) will give you 10-15 HP increase. Or EFI out of early '80's Volvo... That gets you 20-25 more HP.
Also, a stock M10 in the E21 puts you into Class B, almost always, while a 6-cyl or M3 engine will lend you in Class A.
(I'm only advocating for the no-swap option, because I think there isnt' enough E21 representation in our series 
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Passenger seat 6 cyl. solves the nose heavy problem.
Maybe even a 3.0l old Ford sho Yamaha engine
Weld on an entire Neon SRT-4 or Cobalt SS front end from the firewall forward for the world's first FWD E21.
That being said there is a cheap 82 320i 5 SPD on western mass. That's an efi car.
In order to go to a 6-cylinder with a simple swap in, you'd need a different front subframe out of Euro E21 323i (or many hours of fab work). My e21 has seen over 15 races with an M10 and personally I wouldn't go to a 6-cyl engine due to higher front end weight, much higher fuel consumption, tire wear, brake wear... And speaking of being bullet proof: the M10 is on par with any other reliable engine.
Now, where you gain power is dumping the mechanical fuel injection system for something different: an old Weber with the intake manifold from a 2002 (bolt on, but need to change a fuel pump form high pressure to low pressure one) will give you 10-15 HP increase. Or EFI out of early '80's Volvo... That gets you 20-25 more HP.
Also, a stock M10 in the E21 puts you into Class B, almost always, while a 6-cyl or M3 engine will lend you in Class A.
(I'm only advocating for the no-swap option, because I think there isnt' enough E21 representation in our series
I'm not racing an E21 or 2002 in Lemons, but looking for a Lemony solution to making my wife's '73 2002 more reliable and a bit more powerful. It has the original M10 but with a Weber 32/36 DGAV currently.
I snagged an intake manifold, fuel rail, throttle body, etc from an early E30 318i (final version of the M10 IIRC). Any reason you guys don't use those parts on your E21? Like with Megasquirt (or Volvo Bosch LH2.2 as you suggested)? Seems like a pretty simple upgrade worth the small expense to get the parts. Just wondering if there is some better solution for more modern engine management. Thanks.
My M10 uses an E30 intake manifold and modified fuel rail (removed fuel pressure regulator and replaced it with a cheap ebay one that allows a manual adjustment to the fuel pressure for tuning). Other parts (MAF, throttle body, throttle position sensor, wiring harness, brain box, bosch injectors) are Volvo-sourced. I also needed to plug the ports for mechanical fuel injection system's injectors with bolts and JB Weld that are in the head (rather than in the intake manifold), but that's not an issue with the 2002s. IIRC, the otherr sensors (water temp and O2) are interchangable between E21 and Volvo system (both are Bosch).
Other option was to use the EFI from the early E30s, but we had Volvo parts laying around . The main difference is that the Volvo system uses a signal for distributor to determine the crankshaft position, while the E30 system has a dedicated sensor.
Great, thanks for the reply pyvo13. Sounds like I've been thinking along the same lines. I want to use most of the hardware from the E30 318i (M10) and then choose appropriate sensors for whatever engine management I decide on. I appreciate the feedback. Sadly the 2002 in question is not a Lemons car, and has no plans to become one.
We plan to return to Sonoma in March. Stop by our paddock - we'll have a beer while pointing fingers at various parts under the hood
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