Need advice from experience for an M42 rebuild

[jaredmac11]

M42 heads are around, I have 2 just sitting (one with Schricks and all the top end goodies), so just make a WTB.

Save it for me! Have you had this head in a running car? what did you get from the Schrick cams? I thought BMW already had pretty tall cam lobes?

I have an e36 head on my e30. I had read that the E36 is actually not as performance oriented as the E30 cam but I never confirmed with a gauge. I can say that the e36 valves are lighter with the e36.

[jaredmac11]

From an environmental perspective alone, DEFINITELY drain all the fluids. From an ease of cleanup you should do it as well. Ill never forget when I had my M42 on the engine stand and turned it upside down and lost another quart of fluid.

I had about 6 bags of kitty litter in my garage for that project...

[JonsE30]

its been a couple days since i drained the oil to find out that it is milky. do i need to do an engine flush to get all that crap out before i get started pulling off stuff?

will the coolant/water that got mixed with the oil damage any of the internals?

[JonsE30]

roguetoaster, i PM'd you.

[roguetoaster]

Cool, if you can't dig one up locally keep me in mind as a source.

[JonsE30]

I put out a WTB thread.

https://www.r3vlimited.com/board/showpost.php?p=4910890&postcount=1

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[roguetoaster]

You can use the starter (jump with 12v) to spin a replacement engine if it's out and you want to do a compression test. It's an iffy procedure, but doable, I suggest buying from a trustworthy person instead.

M42 heads are around, I have 2 just sitting (one with Schricks and all the top end goodies), so just make a WTB.

This would also be a great time to swap to another engine if you want, but you should 100% read up on CA BAR. My suggestion for an optimal swap is an M54 instead of an M50/52. Slightly more work, but probably better overall.

[JonsE30]

slowmoe30,

that's exactly how I feel to about swapping an engine gambling on its health since your spending all that time for it to be a bad engine after it's all buttoned up then I'm back to square one.

I just don't see m42 heads for sale as often as m50's. i also don't know how much more complicated it would be to make it street/smog legal. CA has strict laws about this stuff, but I read getting it "BAR'd" is just like a more involved inspection, but I don't know much since I've never done it.


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[JonsE30]

Need advice from experience for an M42 rebuild

jaredmac11,

so if I go with an m50 swap it would be best that it is still in the car so I can do a compression test and if it's good have them take it out?

a lot of the ones I see on Craigslist are already out described as "pulled from wrecked car" that had XXX,000 miles. is there no way to test the health of the engine once it's out? or do I have to take the seller's word for it?



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[slowmoe30]

New head = more time, risky because you'll do a lot of the work. This can be managed if you are cautious and thorough.

Swap engine = less time, more risky IMO because the engine may be a wild card.

Since time isn't an issue for you, I'd recommend to take the head out, in-car. You'll learn a lot about your engine when you do this job. Take the time, be cautious and thorough.

Get the head out and get it inspected. Depending on what's wrong with it, best to worst, you'll get a new gasket, get your head machined, or get a new head.

Also, because you'll be working on aluminum parts, FOLLOW TORQUE ORDER AND TORQUE SPECS ON ALL FASTENERS.

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[jaredmac11]

If you do want to go the route of a rebuilt M42 its going to cost a ballpark of $2000-4000, depending on how much you do yourself and how far you go.

From a cost perspective its cheaper to do a complete swap but food for thought, my engine was 150k miles and needed rings at cylinder 1, had a cracked head, etc.

Just because its half the miles doesnt mean its half the wear. Make sure its running and see if you can get a compression test done before the engine is out. I dont know where I sit with the majority, but I feel like most M42 are a time-bomb with their timing rails and that should be at least reviewed with any work.

[JonsE30]

gotcha. I'll try to source a whole engine for swap. thanks for the info.


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[roguetoaster]

If your head is cracked, yes.

[JonsE30]

oh. I didn't know that about the cracked head.
so i need to source a non cracked/warped head or a working m42 complete engine which then after I do the rebuild?

[roguetoaster]

roguetoaster, yeah i immediately expect a cracked head and to get the head re-machined.


how less expensive will a working m42 cost? maybe i can just swap that in and pull mine out and rebuild it on the side if the extra cost isn't too unreasonable.


when you say a "whole other working m42" do you mean i just swap heads? or like the entire swap?

Machining the head won't fix a cracked head, you'll need a replacement if your is cracked. In theory it can be welded, but it's not economical.

A whole engine swap is faster. Yes, you could swap heads, but I'd prefer to keep an intact, working engine as is and not monkey with it. Expect to pay $2-400 for a cylinder head, and $3-600 for an engine depending on you local market.

If the whole engine needed nothing you'd save a few hundred or more over a head swap depending on how much maintenance you have to do once you tear yours down. However, chances are an engine that was pulled will need a bit of love at least.