M30B32 Valve Hit Piston. Broken Rocker Arm

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Cartermatson
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Joined: Jul 12, 2021 12:12 AM
Location: Seattle

M30B32 Valve Hit Piston. Broken Rocker Arm

Post by Cartermatson »

Hello everyone, first time posting here but just thought I'd get on here to share my project and if anyone has any input I'm all ears cause this is my first time doing any of this.

I have an 83' 533i which I use to drift, and beat the ever living crap out of. It's mostly only a track car but Its insured and I don't have a trailer so I do drive it to and from the track, actually only got to once since this happened at my first track event sadly. A couple hours in It sounded like it was misfiring pretty badly, so I called it a day and went home. Checked spark first and nothing wrong, so I pull off the valve cover and sure enough, broken rocker arm on exhaust valve cylinder 1. I just finished pulling the head and also noticed the piston hit the valve a little, I'm guessing the valve floated a bit and would make sense that the shock broke the rocker arm. Also the cam is completely chewed up on that first lobe where the rocker arm broke.

I plan to keep the piston, the cylinders look good otherwise, but I've read mixed opinions on sanding down the burr where the valve hit the piston to reduce the chance of hot spots, so I'm not sure if I should just leave it or take my chances with using something to sand it down?

going to disassemble the head and send it to a machine shop for a valve job soon. New valves, guides, camshaft (probably something with more lift but undecided), heavy duty springs and rocker arms, all hopefully I can get through Ireland Engineering. Also taking into account the fact that I plan to run a small turbo in the future I'm putting in an MLS gasket and ARP headstuds.

But what I'm really wondering Is.. is this more trouble than it's really worth? Am I just pouring money down the drain or will I end up with I motor worth putting some boost into? Not sure but I do like the motor and swapping it out still sounds more expensive and like more work at this point.

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Mike W.
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Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: M30B32 Valve Hit Piston. Broken Rocker Arm

Post by Mike W. »

The 3.3 is a good engine, stock it has a bit more punch than the 3.5, but with lower compression and slightly larger displacement, the 3.5 is a better choice for boosted.

Looking at things it appears it was run for some time with a loose or missing cam oiler bolt, it's got significant wear on both cam lobes. The chipping is probably from when it broke, but not the wear. Some like to crimp the oiler tube in the middle thinking somehow that will get more oil to #1, but I'm not a fan of that. What I do is drill out the little tiny hole for oiling #1 cam lobes to 1/16 of an inch. Only the #1 as that's the only one that seems to be a problem. Also FWIW, the intake valve kissed the piston a bit and even more on #3. Not enough to be a problem, nor is the mark from the exhaust which I'd just take the end of a file to and kind of scrape flat while leaving the dished part as is. Not the flat, the end like a chisel. A file is hard enough to cut a little of the aluminum away, but not so sharp as to dig in.

Mission creep, but I'd dig in there and replace the timing chain guide. They can get brittle with age and occasionally cause a lot of problems when they break apart. The tensioner rail I'd probably leave as is, I've heard there is a shortage and they rarely seem to be a problem. Even if they're grooved and look like crap, they don't seem to be a problem.
tschultz
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Re: M30B32 Valve Hit Piston. Broken Rocker Arm

Post by tschultz »

I haven't tested but wouldn't discount the 3.3 for FI. It has thicker cylinder walls due to the smaller bore so theoretically less chance of leakage between cylinders. Some previous people on this forum have had good success with them and a turbo. I have a bottom end that I removed for the 3.4 just because I wanted to start with TCD timing chip and turbo (RRFPR) at a low cost to entry.

All M30's are subject to the rocker problem unless you upgrade them, so aim for lower rpm beating and they should hold up. It seems the stock ones can fail at high rpm and rev limit hits.

Now I am building a 3.5 with 9:1 compression but I plan to keep boost below 10psi. Mainly, I wanted a bit quicker spool and better off boost performance when up in the mountains. Too much turbo lag at 10,000+ft with the 8:1 and my A/A intercooler. This is 65% (or less) the air available at sea level. Hoping for similar torque and horsepower at a lower boost level, with the off boost component being a big piece to my reasoning to swap pistons into my spare 3.4 block.
turbodan
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Joined: Jan 09, 2007 10:19 PM

Re: M30B32 Valve Hit Piston. Broken Rocker Arm

Post by turbodan »

Your best choice for boost would be a stock B34 or B35 cam. No need for more lift, boost handles cylinder filling quite well. More lift means more stress on valvetrain components and since power will be no issue on account of forced induction it doesn't make sense to compromise. In any case, make sure you're running a suitable oil with appropriate viscosity and a good additive package with the new head. These motors were designed for 20w50 and ZDDP, which you can find with Valvoline VR1 or Castrol GTX Classic. Mobil 1 15w50 isn't bad either but it's a little lower on zinc. For colder climates, I would go Mobil 1.

The main challenge with boost is controlling detonation, which the M30 doesn't put up with as well as the M20. If you can lower the CR toward B34 territory you will have a greater margin of safety with forced induction.

As far as the piston, just knock the edge off of the divot with a little filing or sandpaper. It is likely inconsequential as it is but it also wouldn't hurt to smooth out.
Mike W.
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Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: M30B32 Valve Hit Piston. Broken Rocker Arm

Post by Mike W. »

tschultz wrote: Mar 27, 2023 11:25 AM I haven't tested but wouldn't discount the 3.3 for FI. It has thicker cylinder walls due to the smaller bore so theoretically less chance of leakage between cylinders.
While there is more space between the edge of the cylinders which may or may not give a more stable head gasket, the cylinder walls are about the same thickness, it's a different block casting for the specific bore, not a generic M30 that they just bore to need. Which is why the blocks have cast in them 2.5/2.8 or 3.0/3.3 or 3.5 depending on if they were to be used for an 86, 89 or 92MM bore.
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