E30 Cabrio Project - Engine - Supsension - Brakes Discussion

[Brew]

Not a problem. Good luck with your project... I'm just digging in to mine this month and I'm psyched.

[iXer]

Bryson speaks the truth. You can come across M50s for a mere $600-800. Rebuilding would be about the same price. Why would the M20 be cheaper? A turbo M20 would cost the same amount as the 24V swap.

The M20 would be cheaper because he already has the engine. A rebuild of either engine is going to cost about the same unless there are serious issues with the M50s 24-valve head and parts need to be replaced.
In the end I firmly believe the M20 turbo is more expensive than a 24-valve swap. Of course that depends on your ability to fabricate some parts yourself and use the junkyards, additionally you may have a different standard of quality when it comes to what is a good turbo setup. An aftermarket engine management system is required with a turbo setup, not so if you go N/A M50.

About O-ringing the head or block, a copper head gasket would be like throwing away money, the stock head gasket with O-ringing and head studs is perfectly safe up to what I consider ridiculous power levels in an E30 (400+ hp). It's all about preventing detonation. Good engine management will help here and this is where you should lay down the cash (tuning).

/Mattias

[Addissimo]

Also take into consideration the cost to tune the engine management software. If you want it street tuned, your looking at about $240 (4 hours @ $60/hr) or more. If you want it dyno tuned, you're looking at a minimum of $90/hr (in the shops i've seen). When it comes to the weight differences, the difference between the m20 and the m50 is only about 50lbs (136kg for the m50 and 117kg for the m20) once you add the turbo setup to the m20, you'll easily surpass the weight of an m50.

I've been trying to decide which way to go for a while now, and now that I've bent a valve, I'm thinking its a good time to do so. My decision is the m50, its cheaper and easier, and it probably won't get me into as much trouble as a turbo m20 would.

[Mystikal]

My decision is the m50, its cheaper and easier, and it probably won't get me into as much trouble as a turbo m20 would.

With wayyyy less power. Turbo M20 is to an M50 as an M50 is to an M42.