School me. M20 + Carbs?

[lumbergh17]

So I've been doing some searching lately out of curiousity and came across some m20's running carbs. I've seen some holley setup's, triple carbs, etc. This really caught my attention as I have a lead on 2.5l m20 (out of an e30) and I currently have two Weber 40's. So I was thinking a triple weber m20 would be pretty cool and at the same time keep an old school appeal.

My question is I could obviously bolt up the weber's but where would I go from there?

I couldn't really find solid info, but what I've gathered is the e21 m20's have a distributor and the newer e30 m20's don't? So then what would I do for spark? What other problems would I face? (Obviously money, brake booster location)

Please discuss and add your thoughts because I'm a bit confused. I realize tuning triple Weber's would be hard to tune but man would they sound awesome.

[Pierre]

So I've been doing some searching lately out of curiousity and came across some m20's running carbs. I've seen some holley setup's, triple carbs, etc. This really caught my attention as I have a lead on 2.5l m20 (out of an e30) and I currently have two Weber 40's. So I was thinking a triple weber m20 would be pretty cool and at the same time keep an old school appeal.

My question is I could obviously bolt up the weber's but where would I go from there?

I couldn't really find solid info, but what I've gathered is the e21 m20's have a distributor and the newer e30 m20's don't? So then what would I do for spark? What other problems would I face? (Obviously money, brake booster location)

Please discuss and add your thoughts because I'm a bit confused. I realize tuning triple Weber's would be hard to tune but man would they sound awesome.

Both the E21 M20 and the E30 M20 have distributors. The difference is the location. On the E21, it's off the side of the block on the driver's side driven by the timing belt. On the E30, it's on the end of the cam at the front of the head. (I guess, it's technically driven by the timing belt too.)

My simple question is: WHY???? If you want performance beyond the stock setup, use a megasquirt. But carburetors?

I guess if your started with an E21 engine, you could replace the old K-jet with carbs. But if you have a motronic motor, keep the injection system. For one thing, the ECU controls your ignition too. Get a chip, higher flow injectors, a free flowing air box and exhaust. The whole thing fits in a 2002 with no relocation of booster, and cost will be less than a carb conversion.

[TobyB]

Sure, you could do it. Sure, it'd be fun.

The M20's no sportenmoteur, that's fer sure, so if it makes

you grin, do it.

But Pierre's right, from a lot of perspectives, it's a step backwards...

t

[MAD02]

If you're serious about running carbs you can get the intake manifold from a BMW 320/6. This was an E21 with a 2 liter M20 and a carb. There is a guy on Bimmerforums running a Holley 4 barrel carb with one.

Edit: Here is the thread......

http://forums.bimmerforums.com/forum/showthread.php?t=1179439

[02for2]

As Toby said, it's a step backwards... why??

Carbs, while good enough for the 1st century of the automobile are not at all dynamic. They cannot conform to changing parameters. EFI on the other hand, even in it's most rudamentary forms, offers some degree of dynamic response.

Again, as Toby portends, the M20 is no screamer, even with EFI. IMHO, add carbs and you have a true Love/Hate going on.

Cheers!

[Pierre]

As Toby said, it's a step backwards... why??

Carbs, while good enough for the 1st century of the automobile are not at all dynamic. They cannot conform to changing parameters. EFI on the other hand, even in it's most rudamentary forms, offers some degree of dynamic response.

Again, as Toby portends, the M20 is no screamer, even with EFI. IMHO, add carbs and you have a true Love/Hate going on.

Cheers!

A stock M20 with a chip, different injectors, free flow intake and exhaust, no power steering pump or AC compressor and a deleted fan can be a screamer. (185 HP)

Put it in a 2002, and it's plenty fun.

M20 can also be built with pistons, cams, porting, throttle body etc. A built 2.7i will embarrass an S14 at the fraction of the cost.

[02for2]

No doubt! I agree 100%!

But stock, it's no hair ignitor. How do I know? I run a stock M20 in my E30 325is.

No Doubt, a 'built' M20 will get your attention. But the same can be said for virtually anything from a 50cc Tucumseh to an LS1.

However, I cannot imagine a favorable cost/benefit ratio of building an M20 around a set of carbs.

Cheers!

[NickVyse]

My simple question is: WHY????

Because apart from going like stink they sound incredible and look cool as fuck. If he's worried about efficiency then he's on the wrong forum ;-)

Full build thread on this car here - it gives you a fixed grin whenever you're in it:

http://www.02forum.co.uk/viewtopic.php?f=11&t=1415

[daniswaytough]

because any cool car from the 60's with an inline six would have had triple sidedraft webbers.

that's why.

it's something i'd like to do. build up a stroked m20, headwork, etc, then install the triple webbers.

it'd be a money pit, but you'd have the coolest dam engine of any 02 ever

i wonder how'd the airfloor to the furthest webber back would be, i imagine that would be a bit tricky...

[lumbergh17]

So I've been doing some searching lately out of curiousity and came across some m20's running carbs. I've seen some holley setup's, triple carbs, etc. This really caught my attention as I have a lead on 2.5l m20 (out of an e30) and I currently have two Weber 40's. So I was thinking a triple weber m20 would be pretty cool and at the same time keep an old school appeal.

My question is I could obviously bolt up the weber's but where would I go from there?

I couldn't really find solid info, but what I've gathered is the e21 m20's have a distributor and the newer e30 m20's don't? So then what would I do for spark? What other problems would I face? (Obviously money, brake booster location)

Please discuss and add your thoughts because I'm a bit confused. I realize tuning triple Weber's would be hard to tune but man would they sound awesome.

Both the E21 M20 and the E30 M20 have distributors. The difference is the location. On the E21, it's off the side of the block on the driver's side driven by the timing belt. On the E30, it's on the end of the cam at the front of the head. (I guess, it's technically driven by the timing belt too.)

My simple question is: WHY???? If you want performance beyond the stock setup, use a megasquirt. But carburetors?

I guess if your started with an E21 engine, you could replace the old K-jet with carbs. But if you have a motronic motor, keep the injection system. For one thing, the ECU controls your ignition too. Get a chip, higher flow injectors, a free flowing air box and exhaust. The whole thing fits in a 2002 with no relocation of booster, and cost will be less than a carb conversion.

I understand what you are saying and it wouldn't exactly be for performance, but more just for the carbed m20 aspect? I'm confused again mostly on my lack on knowledge but how would I control ignition then if I got rid of motronic?

Maybe I should just sell the carbs and use the money towards the swap...

[02for2]

You'd likely have to use a crank trigger for the spark and a speed sensor or some such to a control box for the advance.

It won't be easy or cheap to get it working well, but it's certainly doable and an interesting project.

Cheers!

[lumbergh17]

You'd likely have to use a crank trigger for the spark and a speed sensor or some such to a control box for the advance.

It won't be easy or cheap to get it working well, but it's certainly doable and an interesting project.

Cheers!

I see, would this be more along the lines of what they did for the carb'd m20's in the e21's? I think it'd be a fun project to do on the side, I mean I have some of the parts.

[Kpeters]

I have a gray market E21 6 cylinder that came with the Solex 4A1 4 barrel carb and we put in a 2.7 stroker engine on it with that same carb.

The car is a beast VERY quick and huge amounts of torque. The carb is delicate but works beautiful if properly tuned. You can get one out of an old Mercedes Benz.

Some notes:

1) E21 and Early E30 had regular distributors newer ones had motronic distributors on the front of the engine but kept the original distributor shaft on the block so you can put the regular distributor there! (That's what I did) Just take off the cap, put in the distributor.

2) 4 barrel setup is awesome on M20 but you can always go with 3 Webber 50's or 45's sidedraft!

If you need any help give me a call I'd be glad to let you know how it went for me.

Konrad.

[SRC60]

As Konrad said, you can use a distributor from an e21 320/6 or 323 or a Euro e30 323 also used a similiar distributor. For clearance issues, triple Weber downdrafts would be a better choice over the sidedrafts. But, they will be expensive. The 320/6 manifold with either the stock Solex or modified for either a Holley or Q-jet would be much simpler and cheaper.

I agree with the others though - modern fuel injection, either stock Motronic or aftermarket like megasquirt would be a 'better' choice. That said, I am working on modifying a 320/6 manifold for either a Holley or Q-jet for a m20 for my 2002. It just seems to be a better fit than all the electronics.

Steve.

[NickVyse]

any economy issues get quickly forgotten when you open the bonnet