M42 vs. M20

[tehwickerman]

I have a 318IS and 325IS.
I love them both dearly. They are both in great running condition(did complete timing belt/chain replacements and all the good stuff that goes along with that, valve adjustment, seals, mess under the intake etc etc.) and I will soon be putting a 5 speed in the 325 out of my parts car, and are both cosmetically very good too. (325 is schwarz, 318 is sterling which I kind of like better... and it's rare)
However, I need to decide which one I'm going to perform a bunch of "tasteful mods on" (shocks/springs/you know the drill).
I like the 6's performance #'s but I still need to put the lightened flywheel on the M42... How big of a difference does this really make? Is it like... almost enough to keep up with a 325 with a 4.10 LSD? What other tweaks can I do to the engine without spending major bucks to get some additional power? I'll probably end up modding the 318 just because of the rarity factor, but I do enjoy the "occasional" spirited drive so I'm having a hard time deciding.
Any input is appreciated. Thanks.

[Hick]

id say the 325.

[gearheadE30]

I personally would mod the M42 unless you want to stroke or turbo the M20 for serious power.

Power from an M42 is pretty much limited to Mustang injectors, electric fan mod, chip (markD is the best imho), ltw flywheel is huge, and a freer-flowing muffler. This is the easy cheap stuff but will only net you around 145-150 hp at the crank. The M42 is a lighter car and is balanced better though, to a noticeable degree. The m20 with a 4.10 will be about the same or quicker.

A stroked M42 with an M47 crank and M/S52 pistons will probly get you to 180 crank based on what I have seen. Either way, the 318is is a momentum car, but they are very rewarding to drive. Then again, you did post this in the M42 section :)

[Erick]

I am fairly new to M42s, but wouldn't a chip alone bring you from 138 to 145-150hp at the crank? Then you can add in all the extra small stuff. I was hoping to see an M42 with bolt ons at around 160-170hp at the crank. (at a very high rpm :p)

- Erick

[tehwickerman]

Yeah, to be honest I'm kind of biased to the 318 at the moment. It's just such a well built/well engineered little engine, and I really like the handling. I'm sure new shocks and springs will make it even more enjoyable.
I know in the long run an M20 is much easier to mod to get large amounts of power out of though. Ahhh decisions are a bitch. I know the 318 will be come a "collecters car" more quickly then the 325 as well.

[Hick]

im working on the stroked m42 motor. i still dont think it will have as much potential as a relativly stock m20. my gf has an 88 325is with ACS springs and billy sports. it drives well, and puts the power down great. the m20 motor is more than enough [IMO] for the e30.

while m42's are lighter by compairison, they do show it in the corners, the m20 powered cars can be sorted out to work just as well.

[tehwickerman]

My M20 is actually already stroked to 2.7L. It does 0-60 in 8 seconds with a pretty much shot autotragic transmission+a fucking stupid exhaust where the past owner chopped off the dual pipes in favor of a single pipe catback.. so the power is getting raped pretty hard. I'm sure once I put on new pipes (possibly new headers) and the transmission it'll be pretty damn quick.

[Erick]

I'd hardly say the M42 is better designed than the M20. Newer technology, dual cams, yes. But in the long run an M20 seems much more reliable (better built) than the M42.

- Erick

[tehwickerman]

Yeah I suppose.
I'll really have to wait till I get the 5 speed in the 325 to make any final judgements.
This is kind of a noob question but is it normal for the valves to tick on the m20? I've only heard a few run and they all seem to do the same thing, but I'm wondering if I'm still slightly out of adjustment or something. Kinda in the wrong section to ask this.. oh well.

[Erick]

I've yet to hear an M20 that doesn't tick. I heard one once that barely did, but it was still noticeable from while riding along inside the car.

[tehwickerman]

Okay, thanks for the info and input guys. Kinda annoying sounding like theres a diesel under the hood but oh well :P.

[Erick]

Wait... if it sounds like a diesel it's a different story. Either you're exaggerating or there's something seriously wrong with your valves. There's a difference between light ticking and basically clanking on your motor.

[tehwickerman]

I'm overexaggerating... it's a very light ticking, actually more quite then some of the other M20's I've heard

[gearheadE30]

I'm being pretty conservative with my power estimates probably, mainly because I've only seen one or two on the dyno. The m20 will get you more power, no doubt, and, timing belt aside, both motors are very reliable. There is just a lot more out there for the M20 and they displace more, so power is naturally easier to come by. Check out Metric Mechanic for some insanely well-built (and insanely expensive) M42s.

[theox69]

Start modding your 325is.
That way you can use your 318is as a more conservative, fuel-efficient daily driver.