Rebuilding M42 need some advice

[forrer13]

Hi Guys,

About a month ago I picked up a 91 E30 with 150K miles with a locked up engine for $600. Body is good with no rust or major dents, and the interior is in good shape. I towed the car home and proceded to pull the engine apart.
It looks to me like a plug broke off in #4 cylinder, bounced around in there for a while then broke off a valve, which destroyed the piston and locked up the engine.

So last Sunday a friend and myself pulled a M42 engine from another 91 E30 at the Pick and Pull (Pick and Pray) paid $225 for it and hauled it home.
My original plan was to clean up the JY engine and drop it in the car, but after closer inspection of that engine, I have found the thrust bearing on the crank is worn and now the crank has too much end play. I could change the bearings but the crank is worn too bad where the bearing rubs. Unfortunately there was no way to tell how many miles were on the JY engine, because the interior had already been gutted.

So here come my questions.

The original engine (the locked up one) has zero crank end play, and the thrust bearing and crank surface look great so I would like to use this crank, and mate it to the pistons out of the JY engine.

1. Do I need to have the crank and pistons balanced as a set?

2. What are the chances of the engine locking up damaging the crank?

3. Should I use block from the locked up engine because it is the factory mate to the crank, or the block from the JY engine?

4. Should I have the block cleaned and honed? or just wipe the bores down with a scotch brite pad?

This car is my 3rd car and is simply a project car, I already have a E46 330i and an old S10 DD. This car will eventually replace my S10 as a DD, maybe by next summer. I have done a lot of mechanical car work in the past but never an engine swap / rebuild.

Thanks for your help, I have a feeling this won't be my first post here.

Have a look at my photobucket pics.
http://s604.photobucket.com/albums/tt130/forrer13/91%20BMW%20318i/

[nicknikolovski]

I would take the block from the locked up engine, get it cleaned up, checked for damage, then if ok get the block measured for all the required tolerances and then use the good crank, and then simply get the crank ground to the next available oversize main bearings if required. The key is to check whether everything is in spec. If required you can could also go to the next available piston size but this would mean making the bores bigger. Also oversize head gasket is required.
You can get the crank, conrods & pistons balanced together as a set but I don't think its necessary unless you want to build a race car.

[forrer13]

I would take the block from the locked up engine, get it cleaned up, checked for damage, then if ok get the block measured for all the required tolerances and then use the good crank, and then simply get the crank ground to the next available oversize main bearings if required. The key is to check whether everything is in spec. If required you can could also go to the next available piston size but this would mean making the bores bigger. Also oversize head gasket is required.
You can get the crank, conrods & pistons balanced together as a set but I don't think its necessary unless you want to build a race car.

Thanks Nik,
I dont think I want to go to bigger pistons, as I am on somewhat of a budget. As far as I can tell the bearing journals and cylinder bores look ok as far as scratches or damage, infact the cylinders still show their hone marks. Its probably worth spending the time and money to get the block cleaned and honed, and to have the crank checked out before assembly.

I am in no hurry and I have to save my $$$ this month as we are leaving for Aus at the end of the month.

On a different note, where in Melb are you? I live in the Cincinnati area now (Ohio), and have done for the last 20 years, but I was born in Melb (Ferntree Gully) and grew up in Gippsland (Trafalgar). Dad still lives in Melb (Patterson Lakes) and Mum is up north. Its funny that my first response was from another Aussie (I still call Australia home - Peter Allen)

[Ramblin MAn]

Hey forrer13, Where in Cincinnati are you I am also in Cincinnati. I've taken parts off that same 318i.

[forrer13]

Hey forrer13, Where in Cincinnati are you I am also in Cincinnati. I've taken parts off that same 318i.

So your the guy who got my PS pump and alternator.....JK, I have spares....You don't remember if the dash was in the car when you were there do you? I would love to know how many miles are on the engine.
Hamilton actually.

[nicknikolovski]

Hey Peter, I am out west of Melbourne in Hoppers Crossing.