M20 questions

[tjclemens2]

Hello,
I’m looking to buy a used m20b25 for a swap and I have a few questions. First off, is there a big difference in performance between the 12v and 24v. I was told 24v came in the 325i and z1 and the 12v came of the 5 series 525i. Also if I buy a used m20, what should I go through and check? Should I tear the whole engine down and do a complete check? I want this thing to look nice and to be reliable but I don’t want to drop thousands to rebuild it if it’s not necessary. Finally what are the major fail points of the M20 just so that when I have it out on the engine stand I can do all of the work that needs to be done to make it super reliable! Thanks!!

[digger]

The m20 is 12V only from BMW. There was a racing dynamics project for 24V head but that's a moot point.

I would probably make sure the m20 was from an E30 just to make things simpler, the one from 5 series is slightly different for the ancillary's, motor mount brackets etc iirc but the internal guts are the same.

what are you trying to do? just do a quick swap of a half decent running/known engine on the cheap or rebuild for long term use? if possible try to see an engine running before purchasing that way you can minimise what checks need to be done

[tjclemens2]

The m20 is 12V only from BMW. There was a racing dynamics project for 24V head but that's a moot point.

I would probably make sure the m20 was from an E30 just to make things simpler, the one from 5 series is slightly different for the ancillary's, motor mount brackets etc iirc but the internal guts are the same.

what are you trying to do? just do a quick swap of a half decent running/known engine on the cheap or rebuild for long term use? if possible try to see an engine running before purchasing that way you can minimise what checks need to be done

hey, that’s for the info on the vaulves and diffrent layout of 5 series. I want to go through it and make sure it’s good for long term. Not sure if I want to do a full tear down, but also there is a start of me that says hey I have it out might as well take my time do it right and have a rock solid engine. I feel confident in rebuilding an engine because I have done it once before. Only thing is I’m a broke 16 year old who is trying to do things on the cheap;)