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Cylinder Head question, M54B30 swap

8K views 9 replies 3 participants last post by  Bali 
#1 ·
Hi guys!


I have a very tired M54B25 in my car, running fine (mostly).

Got myself a 3.0 complete swap a few months ago. Plan was to install it later this month. I'm in the middle of rebuilding it and discovered the head is warped (bowed). The block threads are still good and the surface is straight.

I know the 3.0 cams are bigger so I will be wanting to keep those.

My new plan is to use the head off of my 2.5 that is in good shape, and swap the cams over.

My question is, how should I swap the cams? Just swap cams? or swap cams and the cam troughs (I don't know correct term)?

Is there anything I am giving up by using the 2.5 head? Valve size? Port size?


Can't wait to have a 3.0 Touring.

Thanks,
Jacob
 
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#4 ·
I never put mystery motors into cars. Rings and bearings are efforless to do when it's on a stand. And then all new gaskets, cleaning out the oil and coolant passages...

I bought the motor already torn apart.

Block was fine. Some thing scuffed main bearing 6. But the crank was good.

I did end up swapping the 3.0 cams and springs over.

Head install is in a holding pattern. Pulled a thread in the block. All the bolts did the 40NM fine, and the first 90 degree turn. It was the second 90 that killed the first bolt.

So now it's getting time serts. I am a CNC Machinist, have all the tools to do it, just not the inserts yet.
 
#5 ·
All sounds good. Much respect. Growing up my Dad was a machinist; our garage had a milling machine, lathe, arc welder, oxy-acetelene welder, band saw, surface plate, gauge blocks, endless tools, you name it. Could barely park a bicycle in there!

Hey, one thing I’ve seen others do in previous rebuilds is to use head studs instead of bolts to avoid the potential thread pull in final torque down. Is that something you’re considering?
 
#6 ·
I think I should probably update this.

I just used head bolts, a stock motor really shouldn't need studs... I was successful at putting the timeserts in. If I was doing it again, I would have gotten 30mm long ones instead of the 24mm ones someone was selling on amazon.

I got the motor fired up, it has about 200 miles on it now, even got it past emissions testing. Still running the 2.5 tune (which was updated in 07 according to my PA Soft log). Engine runs real smooth, except sometimes at WOT it hesitates. Plan is to flash the 3.0 tune tomorrow.

So, I guess the answer to my original question is, springs and cams. Though I am not 100% sure on the springs thing, just going off what others claim. the 2.5 and 3.0 heads had the same number of coils on the springs, and the thickness of the coils were the same, which should mean the same spring rate and same compression height.

I had headers on my 2.5 since it had clogged the cats, the 3.0 with the 2.5 tune and cats feels like it has a decent amount more torque, but not so much high end.
 
#9 ·
I just finished swapping a 04 Zhp everything into my 02 325iT. Having just a few issues and wondering if the Zhp lcm could possibly be the problem. Dim tail lights, cooling fan not turning on. Warning lights for brakes, yellow brake light


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