M42 budget rebuild - Upgrades to bottom end?

[Martin C.]

OP, I'm going through this exact operation right now. So far I know we need new sets of rod/main bearings, and new rod bolts. Still trying to figure out if the main cap bolts can be reused. Also figuring out if it's cheaper to buy the gaskets individually or as a package. I hear that there's an updated crank seal that's of benefit to use. Might even do the piston rings while I'm at it if I can afford them...

Sopunds like you are going deeped into the build than I am. My main problem was the head so I am getting that refreshen. The bottom end was fine for the most part. GL and let us know how it turns out.

[Martin C.]

Thanks Guys. I really appreciate the input regarding upgraded bearings, and updated relief valves. I can see that having a lot of money would probably help me in getting forged pistons, problem is: I do not have the extra cash right now so I am sticking to simple upgrades.

I am not sure but thinking about replacing the oil pump too.

And I know buying the whole gasket set is more cost effective ("cheaper" if you must) than piece meal.

Happy Thanksgiving!

[io_RobbieRodgers]

OP, I'm going through this exact operation right now. So far I know we need new sets of rod/main bearings, and new rod bolts. Still trying to figure out if the main cap bolts can be reused. Also figuring out if it's cheaper to buy the gaskets individually or as a package. I hear that there's an updated crank seal that's of benefit to use. Might even do the piston rings while I'm at it if I can afford them...

[trackjunkie21]

I don't have to write BMW to figure out why they decided to reduce manufacturing costs by installing cast parts. Look at the numbers man. m44 is +4lb/ft of torque over the m42, and that's about it. Was it about performance and longevity or profits??

that's when it's obd2. obd1 conversion yields power. If you really wanna go off the walls, locate an m47 crank.

[Ryann]

The OP asked about simple upgrades for a daily-driver and you're suggesting forged pistons? really?

Fair enough. That IS the plan for mine though.:)

[bwawuz02]

I don't have to write BMW to figure out why they decided to reduce manufacturing costs by installing cast parts.

I'm not disagreeing with you on that one. As with many things, BMW over-engineered in the first iteration and cut the fat later. Just saying that fat trimming doesn't mean the parts aren't as good for their intended use.

The OP asked about simple upgrades for a daily-driver and you're suggesting forged pistons? really? He could get a good M44 crank and pistons for that price and see more gains.

[Ryann]

I don't have to write BMW to figure out why they decided to reduce manufacturing costs by installing cast parts. Look at the numbers man. m44 is +4lb/ft of torque over the m42, and that's about it. Was it about performance and longevity or profits??

[bwawuz02]

the parts you already have are as good or better in most respects? and if you've got the dough replacing OE cast pistons with some forged ones would be a good upgrade.

Maybe you should write BMW a letter and ask them why they changed their design to something not as good. Please let me know when you read about somebodies M44 bottom end coming apart on them. And btw the N55, BMW's turbo engine, uses cast pistons; but it does have direct injection, so... Do some more reading.

M44 = more displacement. I have the money and can piss it away any way I see fit.

Some people make a hobby out of taking things apart, modifying them, and putting them back together.

[Ryann]

I'm not sure why you think the cast parts aren't strong enough?

Why spend the money to source an m44 rotating assembly when the parts you already have are as good or better in most respects?

[Dj Buttchug]

^ the m42 also has oil squirters. fwiw the cast internals will work fine for daily driving. There is really no need to upgrade. The only real improvement to be made here is the 360 thrust bearings.

[bwawuz02]

Not sure why you'd want to replace the m42 forged internals with m44 cast ones.

I'm not sure why you think the cast parts aren't strong enough? Since rod length is the same, you have to run the M44 crank if you're buying off the shelf M44 pistons cuz M44 has longer stroke...

The connecting rods are forged and ~50 grams lighter and the M44 has piston oil squirters. ACTUALLY, if you get a 95 build M42 bottom end(check realoem.com for exact changeover date), it comes with these pieces from the M44. The 95 also has a revised timing setup that uses a rail near the crank sprocket instead of an idler gear, much cheaper and should swap right in to your current M42. The oil relief valve has been updated and is a cheap replacement while you're at it, just order the reg part# and you should get the updated unit.

Everything else has already been mentioned. If you get the M44 crank, keep the timing gear that goes on the rear counterweight or you'll have to add weight back to balance the crank, ~100 grams.

[Dj Buttchug]

I'd replace the crank thrust bearing with the 360˚ m50 piece, and if you've got the dough replacing OE cast pistons with some forged ones would be a good upgrade.

this.

Oil pressure relief valve

and also this. updated plastic relief valve. metal earlier ones tend to stick

[KenC]

The thrust bearing for the M42 was updated so it should be a 360 unit now. I'd just buy a full new set of main and rod bearings.

[twistednut]

Oil pressure relief valve

[///digitalme]

Not sure why you'd want to replace the m42 forged internals with m44 cast ones.

I'd replace the crank thrust bearing with the 360˚ m50 piece, and if you've got the dough replacing OE cast pistons with some forged ones would be a good upgrade.

^^^ this!!! youre better off with m42 bits than m44


thats what im going to do when i change the headgasket on my car..upgrade pistons....