Engine Swap Help in CT

[Rustee21]

Hello everyone,

Ive got an old tired '81 320 with the original m10 1.8L engine. I have been debating between an engine swap (M42) or rebuild of the M10 and increase the HP along the way. I would need help with either route and am wondering if there are any members in the area that like side projects or know of some smaller shops that know what they're doing. Willing to travel out of state for the right situation. Google search is not giving me too much. I appreciate all the help and open to hearing your opinion about stock vs m42!

Thanks,

Mike

[jsull479]

This is kind of an open ended post. There are pros and cons to both options which you can search on the forums. I debated this heavily and ended up rebuilding an M42 and swapping it in. It was a two year process with a lot of research and bugging members on here with questions (you know who you are lol). But I have only driven like 20 miles on it; still trying to iron out some kinks. The swap can be done in a long weekend if you have a complete motor, all the resource, and know what your doing.

Both have been pretty well documented, and members on here will definitely help you with more specific questions if your looking to do the work yourself. If your looking to have someone do the work, you are likely better off going the refresh route of the M10 maybe w/ mega squirt because not many shops are going to want to take on swapping an M42 project unless you have a lot of $$$.

Just my 2 cents, I am sure other will weigh in.

[Rustee21]

I appreciate it! While I am mechanically inclined I have never swapped a non original engine. Or done any sort of fabrication. Wouldn’t want to go 4k deep to mess up something that will even further empty my poor wallet. I’ve read through a lot of the builds here and am leaning towards the m42 way.

[jsull479]

Haha nor was I, hence why its taking me two years. I was keeping a spreadsheet on cost but the number started to get too high and I decided that spreadsheets are for nerds lol.

I am in NY if you decide to go for it and get stuck. I can send you the drawing I came up with for the motor perches when you get to that point (you will have to trim away some metal). I used M20 mounts because they were a lot cheaper than the M42 mounts fyi.

[HappyE21]

If it was up to me, I would stick with the m10, just because it's more simple. The more I researched into m42 swaps the more of a pain in the ass it sounded like, although thats not to say it cant be done easily. I'm in the middle of rebuilding my m10 right now and it's not going so well, but that's probably just my luck. Either route you take will most likely present some roadblocks, but just research the hell out of what you are planning to do before you start.

[okieflats]

Stay with the M10. Overhaul the head. Valve job, guides, seals. Maybe the bottom end is fine.

Then what are your smog requirements? In California we need to keep the K-jet injection for smog. Otherwise I would switch to side draft Webers.

[Jatamansi]

Hey there I'm in a similar boat as you and in CT as well! I agree with HappyE21

I have an '82 with a tired, dirty M10. Just this weekend decided to take out the motor and replace all the old gaskets and brittle hoses. Oh, and clean every last inch of it. The final deciding factor was that I've got the time and the space, so why not?

[Thecatmilton]

I'd go with a honda K series over an m42 at this point. Most M42s are tired and need timing components. M42 parts are also quite expensive and that's why I sold mine before I used it. You can get an adapter to bolt the K series to the stock transmission. You would need to fabricate engine mounts and an oil pan if you didn't feel like buying the e30 one. A k20a has 212hp NA. It would be expensive to make an m10 make that much power.

[Retoropak]

Agree. K24 is an amazing platform. I wish bmw had comparable 4 cylinder. I am doing stroker m42 though. I invested too much in this motor to change to honda K. But when it blows up I will definitely do K24. The timing alone on m42s is roughly $600-800. There is very limited aftermarket support in terms of intake manifolds and cams. The only thing that I like in m42s is the cast iron block. Honda K series needs to be sleeved to reliably support anything north of 400hp

[jjgbmw323]

How about M50? They are available...

[jaredmac11]

Having driven a megasquirt M10 and an M42 swapped E21... Id rebuild your M10 and megasquirt it.
Best bang for your buck.

I did a good m42 swap into my e21 but didnt have room in the budget for a rebuild. So I just plugged in a tired M42 in lieu of a tired M10.

Edit: I should say the engine is fully refreshed but in terms of the block it just got new valve seals. Bottom end is untouched. Was a mistake to not put the project on hold and rebuild it.
As other said, youre stuck with factory cams and the ecu isn't a great tune imo. Just feels slow in midrange rpm.