bmwe21.net forums

Hello all, I'm Pouyan, a long time BMW fan from my childhood.
first of all I want to stress my appreciation to to this community, this website is so helpful for numerous BMW E21 enthusiasts around the world.

1-I'm planning to buy my first BMW, the car which I found is a E21 320/4, with 318i head , but the car runs with the Solex carb.
I want to know what happens to a E21 2.0 block when a 318i head is installed? does it increase compression ratio and if it does, how much? is this a good combination?

2-I have seen some E21 320 with E12 518 head fitted, what are the effects of this combination? again does it increase compression ratio? and how much?

3-in order to make the ignition system more powerful, is it a good idea to use a total of 4 coils ( one for each cylinder ) ? my idea was to install 4 coils, and to join all 4 wires from the 4 coils in one wire and send it to the distributor, and from there to the spark plugs. is it possible and does the standard distributor stand the high demands?

4-is it a better idea to just use a more powerful coil ( from M20 or M30 for example)

5-what is the main cause for an old engine to lose its power? what should I do if I want to bring back all of the 109 horses to the stalls?! I thought of polishing the engine and manifold and fine tuning the carb and ignition system.

thank you

What makes you think the ignition coil is not powerful? If you haven't already got it, just fit an electronic ign system from a later car, and make sure everything is in good shape.

I have a Weber 32/34 for the m10 engine available.

thanks for the reply,
I dont say that the ignition system is not powerful enough at the moment, but I want to improve it in order to make the engine more powerful, I guess using the MSD about 6-7 HP gain would be possible but MSD is so rare in my place and also quite expensive, so a more affordable option to improve ignition and therefore engine output is what I'm looking for.
but an electronic system from a later car is a good idea, from an E30 maybe?
other than that, Im planning to build a very light weight flywheel and a 304 camshaft.
and Im still not sure that the 318i head on the 2.0 block does increase compression or not? I'm not going fot a turbocharger so high compression is a priority. and Im still not sure that if I want to change the pistons to increase compression, would them hit the current head?

thanks again, I'm a bewildered tuner!

There's nothing wrong with the ign system you had, getting more air and fuel into the engine, and igniting it at the right time will yeid better results that a more powerful system. If you're boosting and the air fuel mix in the cylinders is significantly more dense, then it's worth starting to look into ign upgrades, but a properly timed system in good condition with correctly gapped plugs will cover all your normally aspirated needs.

The qualifier there is "Properly timed". A mapped system, like megaspark or similar will allow you to get the ignition sparking in exactly the right moment for all engine load conditions, and that will get you more hp than a more powerful coil will any day.

You'd be better off saving your cash and fitting a new timing chain, to ensure your OE system and timing is correct. M10's lose a lot of power from stretched original timing chains. A fresh m10, with a Weber conversion, decent spark plugs etc, can make 120bhp. An e30 318i engine has the bigger valve head, but there are lots of different m10 piston types, so you'll not to know which work with what head? Also, once you start flowing heads, fitting bigger valves etc, lots of people get better gains by sticking with the stock cam. Added to which you'll be needing steel rockers and adjustable followers. M10's are great engines, but expensive to modify.

There is plenty of info' in the tech' section stickies.