To rebuild or to swap

[Smrtpunk]

I have an 86 325 it has an old burnt out inline 6 in it. I would like to build a car that can run gravel rally stages with it and am curious as to if its worth it to rebuild the engine or if I should source a new engine.

I have the head and the ECU from a 91 325i, I believe it is an i... but cant really remember, a piston came loose from the connecting rod but the head was not damaged! It was a four door auto and someone before me ripped the rear end out of it.

I guess what I'm looking for are some opinions as to what I should do keep the engine and rebuild or find something new and maybe rebuild that. I would like to keep it simple no super complicated swaps.

Cheers,
Ian

[acolella76]

the 86 325 is not going to be an 'i' since they only made eta's in 86. I say unless you're looking for a high hp high compression engine, you should just buy an m20b25 in good condition and keep plenty of oil pans handy.

[325ix]

Or instead of keeping a lot of oil pans handy, buy a skid plate!

[jlevie]

Doing the rebuild yourself by the time you have the machine work done and get all the parts the cost to rebuild will be about the same as a good used engine. And that is if the cylinders aren't worn. If the engine needs to be bored, that and the new pistons alone are what you'll pay for a good used engine.

[acolella76]

Or instead of keeping a lot of oil pans handy, buy a skid plate!

meh, i've seen skid plates get broken. Good to be safe.

[bmwguy325is]

Go buy a 5.0ltr from a mustang and swap it in. The pan is in the right place and they are narrow so you can run headers.

[Keith M]

Go buy a 5.0ltr from a mustang and swap it in. The pan is in the right place and they are narrow so you can run headers.

That sounds interesting.

[MR 325]

Go buy a 5.0ltr from a mustang and swap it in. The pan is in the right place and they are narrow so you can run headers.

I love how easy you make it sound, LOL.

[Smrtpunk]

Lol at the 5.0! I'll be running it in the Canadian Rally Series and the rules stipulate that you can't run an engine from a different manufacturer.

So I guess mating the 91 head to the 86 block would be too hard/not possible/ not worth it? The way I look at it, im not too interested in slapping a used high millage motor into a car that I will enevitably beat the crap out of constantly, thats why the rebuild makes sense. High quality parts, new seals... you know a fresh start

Oh and for sure on the skid plate, im thinking one of those severe duty ones, has anyone tried one? experiences?

To acolella76, funny you mention the oil pan, one of the users on this site I believe its Slapdash mentioned on an earlier post that he broke his pan on a recent rally, Im not too sure what Skid plate he was using but I'm sure he would of had one and still lost his pan.

[The Humjet]

All I can say is tear down the engine see what's what inside the cylinders. Check for cylinder wear, check if its still got the cross hatching. If all is good you probably get away with a light recondition with rings and bearings, gaskets, and all the usual maintenance bits like water & oil pumps and belts.
As for the head get it all recoed. Maybe if the budget isn't too tight you could put HD rockers, tougher valve springs and a more aggressive cam, and adjustable cam gear while your at it. Make sure you use the 325i intake manifold with the i head.
And get some nice headers and chip too get most performance out of your motor.
Don't cheapen out on a rebuild this is what I do for a living. I haven't yet to work on an m20 but I get people bring motors in that have been rebuild at some backyard joint and see cylinders honed out by over a thou. And it shows when you take it out and your getting nasty blowby and burning oil. My mates skyline had his engine built at some random joint and now is filling up 5 catch cans when he takes it to the track which completely ruins your day. His motor is now at our shop getting the errors fixed.
Get it built at a reputable machine shop. And use quality oem parts.