M30B35 rebuild questions

[wickz80]

So I've got an M30B35, early style, out of an 88 e32 735i. I'll be dropping it in my e28 with the full harness from the donor car.

The engine ran OK, it burned some oil when you got off the throttle, but sounded good and made compression around 100 in the cylinders I checked. 250k miles, unknown history.

So far, I've stripped the engine to the short block, but I think I'll be leaving the crank and pistons alone as they look pretty decent. Cylinder walls still have cross hatching. My machinist buddy is decking the head and will rebuild it to OEM spec. My plans are to keep it NA for a year or two, then go for 10-15 lbs boost. I will be using an Elring (OEM) head gasket and ARPs when I put it back together.

My questions:

1. Oil pump -- it is expensive to replace. I intend to check for shaft play soon. Is oil pump failure common? Is it worth replacing, or finding new inner and outer rotors. $0-700

2. Timing chain and oil pump chain. I intend on replacing all tensioners/timing guides. I don't have the lower timing cover off yet, but would y'all recommend changing out the cam/crank/oil pump sprockets and chains as well? $80-300

3. Rear main seal and the front crank seal. Are these worth doing, while I'm at it? I assume so. $0-20

4. Hand-decking the block. I've seen folks online use a car battery and sandpaper to deck a block, while keeping the pistons and everything else in. I'm not 100% against having my buddy doing all new bearings and crank polishing + new piston rings, but this would expensive. Can anyone chime in? $0-1000

5. Clutch. I'm selling the Getrag 260 from the 735i, and swapping on my Getrag 265 from the e28. Flywheel should bolt up, right? I do plan to go turbo eventually, is it worth upgrading the clutch now?

Here are some pictures






Thank you all, this forum is a fantastic resource for these cars.

Dave

[SlickDizzy]

I just went through a lot of this same work. Here's what I did:

1. Absolutely replace the oil pump wear plate and pressure relief spring. Those are a must if you are in there. I also did the inner rotor but that is because the brittle sprocket threads cracked when I removed the sprocket so I had no choice, otherwise I would have left the rotors alone.

2. My 210k mile B35 had sprockets sharp enough to slice my fingertip like a razor blade. Do all of the timing gear including the sprockets and chains, and you will never have to mess with it again.

3. Any time you are this far in an engine it is senseless not to replace the $20 worth of external seals to prevent leaks down the line. Luckily, they are pretty easy to do on the M30. Use quality seals like Elring and do your transmission seals too.

4. I just used a high-quality gasket scraper and made sure the surface was exceedingly clean. Goofing around with a battery and sandpaper sounds like the kind of thing that could do more harm than good. Decking the block properly and doing a full rebuild of the bottom end is well and great if you have the money, but none of these are usual M30 problem areas unless the engine has been abused.

5. All of your B34 parts will bolt onto the B35. This is a good opportunity to upgrade to a lightweight E12 flywheel though (I did and love the better response). As far as doing the clutch upgrade now, when do you plan to go turbo? Next year or "someday"? Personally I would not want to pull the trans again 6 months after doing all this work.

[Mike W.]

M30B35 rebuild questions

Unread postby wickz80 » 22 Feb 2019 16:05
So I've got an M30B35, early style, out of an 88 e32 735i. I'll be dropping it in my e28 with the full harness from the donor car.

The engine ran OK, it burned some oil when you got off the throttle, but sounded good and made compression around 100 in the cylinders I checked. 250k miles, unknown history.

So far, I've stripped the engine to the short block, but I think I'll be leaving the crank and pistons alone as they look pretty decent. Cylinder walls still have cross hatching. My machinist buddy is decking the head and will rebuild it to OEM spec. My plans are to keep it NA for a year or two, then go for 10-15 lbs boost. I will be using an Elring (OEM) head gasket and ARPs when I put it back together.

My questions:

1. Oil pump -- it is expensive to replace. I intend to check for shaft play soon. Is oil pump failure common? Is it worth replacing, or finding new inner and outer rotors. $0-700

Fail? Not exactly. Get weak? yeah. Unless it measures really tight, I'd throw new rotors in it. You will need more oil with a turbo, for the turbo bearing if nothing else.

2. Timing chain and oil pump chain. I intend on replacing all tensioners/timing guides. I don't have the lower timing cover off yet, but would y'all recommend changing out the cam/crank/oil pump sprockets and chains as well? $80-300

A bit of a pain, but yeah, might was well as long as you're in there. You could get by with just a new chain, guide and tensioner. The other stuff is good to do but not essential.

3. Rear main seal and the front crank seal. Are these worth doing, while I'm at it? I assume so. $0-20

Yeah, that's just part of what you do when you do an engine.

4. Hand-decking the block. I've seen folks online use a car battery and sandpaper to deck a block, while keeping the pistons and everything else in. I'm not 100% against having my buddy doing all new bearings and crank polishing + new piston rings, but this would expensive. Can anyone chime in? $0-1000

M30 blocks are pretty stable, I wouldn't even think about trying to deck it unless you throw a level on there and it rocks, which is only going to happen if it's been overheated to an absolutely absurd point. You do want it absolutely clean, I use razor blades. You're not going to hurt cast iron with a razor blade no matter how wild you might get. Getting way out there into things technical, there is actually supposed to be a certain roughness to it. Holds the head gasket in place. There's a spec for it in the BMW manuals. And the head gasket installs dry. Dry means dry, clean the block with lacquer thinner. I've seen gaskets blow due to sealants used on them which allowed the gasket to move more easily I would polish the crank either yourself with crocus cloth or by having the machinist do it. Bearings? Of course! Especially the rods.

5. Clutch. I'm selling the Getrag 260 from the 735i, and swapping on my Getrag 265 from the e28. Flywheel should bolt up, right? I do plan to go turbo eventually, is it worth upgrading the clutch now?

Depends on how much power you're shooting for. If modest, say 240-250HP, a good stock 3.5 clutch should be good enough. Remember BMW overbuilt things in those days and euro 3.5s were 218HP. If you're hoping to push 300 or more... I think you know the answer.

[wickz80]

Mike, Dizzy, thanks for the input.

I've gone ahead and ordered all new sprockets, and chains. Oil pump tension spring, inner rotor, and plate/gasket.

I'll also hold off on decking the block and will remain with stock clutch and flywheel for now. If I decide to go turbo in the future, I'll eventually upgrade the clutch if needed.

I'll be using mostly the B35 accessories as well, they're in better shape. All new shifter bushings and new throwout bearing, clutch pin, etc while I'm in there. Now just to do a bunch of research on wiring this thing up.

Dave