I'll have to take the heads to,a shop and evaluate them. If they cannot be repaired reasonably ($) I'll have to start searching the salvage yards for heads or even a M73 engine like you did recently.
I may have a set available - on my hybrid build I went with M70 heads (in long beach - not too far from you) - let me know how your evaluation goes
I’ve removed the Jesus bolt on the M70, using a 4 foot extension on a 1/2 inch breaker bar. It surprising went pretty smoothly - the real pain was finding the appropriate holder tool in the first place.
Now I need to remove the hub in order to remove the lower timing chain cover.
Is there a trick to pulling it off?
And note - use 10.9 and not 8.8 hardened flange nuts to secure holder. As you can see I busted one trying to back it out. Luckily I will not have to extract this any time soon, as this is my M70.
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Probably shouldn't have taken off the balancer in the first place.
Put it back on and the whole thing will slide right off with some gentle prying on 2 sides.
'91 Dinan 860 Stage III (new 6L engine)
'91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
'91 850i 6sp (mint) (sold)
'90 Dinan 750iL TT stage III (Guido - The Beast)
'94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
'96 850Ci, The George Carlin car
''73 3.0 csi, '08 535i, '03 X5 4.6is
...and a few other non BMW cars
Mine just came off
Soak it in your favorite penetrating oil
Heat
Tap it with a Hammer
Thanks for the advice. I heated the hub with a MAP torch for a minute, sprayed the rear with PB blaster, then reinstalled the balancer, and pried from both sides at the same time. It popped off to my great relief!
Latest snag is the engine hoist. The engine and transmission are prepped for removal. All is disconnected bar the two motor mount top nuts. The boom of my harbor freight 1 ton hoist doesn’t extend over to the center point of the motor.
I imagine I could potentially try to pull the engine out (and reinstall) at an angle - or I could write it up as an expensive mistake and buy the 2 ton hoist with an extra ~foot of reach.
Thoughts?
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Thanks - that’s what I ended up using. A longer hoist would have made it easier, but got it (just) done. Sometimes all you need is for someone to tell you that it’s doable with the tools you have.
Not the most fun job to do single handed. I’m trying not to think about reinstallation in a couple of months time!
A couple of mins before this picture, work almost stopped. The down pipe flanges were rubbing on the passenger side, and wedged up against the steering box on the driver’s side. A few pushes and shoves got it freed up.
I’m going to have some cleaning to do here. There will never be a better time to swap the steering box out either.
M70 foreground, and M73 behind. Next job will be removing the gearbox and starting to strip the M70 of what I need.
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Last edited by petejk; 06-01-2020 at 07:23 PM.
Fun times! I tip my hat to you.
1993 850Ci.....18 years & 165,000 miles and counting!
There was some fun to be had removing the downpipes, and engine mounting brackets to allow the engine to be lowered closer to the ground between the legs of the hoist.
I then ran the transmission jack under the gearbox, and ratchet it tight, so that I could start working on the transmission mounting bolts.
I had purchased an E torx set, thinking that this might be one of the last tool buys I would have to make at this stage in tear down. Having read another thread on this board discussing the perils of stripping these bolts, I cleaned the heads with brake cleaner and a wire brush, and used a breaker with as much precision as I could. 12 bolts, with none stripped was the success story, although I may replace them with new when reassembling.
Removal of the 6 hex bolts securing the clutch was easy by comparison, using nothing more than a 1/4 ratchet.
The previous owner had advised me that clutch had recently been replaced. After looking at the clutch disc this sounds like a tall tale..
I’m hoping that the flywheel can be resurfaced, although I’m not sure if I should trust this to a local firm, with a new one costing $600. Am I worrying unnecessarily, or does anyone have a suggestion of a machine shop that I can fedex this one to won’t screw or up?
And back to the tools - I failed to plan yet again, and have had to order a flywheel locking tool, part # 83300490822. With any luck it will be here by the weekend, so the fun can continue!
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Take off the Flywheel bolts with an 1/2" Impact
I wasn’t able to get leverage to remove the crank pulley from the M73, as every time I tried, the engine simply threatened to tip over.
Temporary installation into the car seemed like the only way I was going to get this done on my own. Here, I’m using the same bracing tool that I used on the M70 (on the M70 remive the pulley and bolt the tool straight onto the hub). 4 feet of leverage got the job done.
Next up was mounting the engines on stands. M10x75mm bolts are the size you need if using a Harbor Freight 1/2 ton stand.
This picture is what I’ve been working towards - both engines mounted up and ready for parts removal and cleaning.
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Spent this afternoon tearing into the M70, with the aim of removing the heads, upper and lower oil pan, lower timing chain cover, and oil pump.
My first challenge cam with removal of the plate that the distributor rotors attach to. PB blaster and about 10 minutes of careful prying each side did the trick. I will have to add $40 of plastic covers that cracked during removal to the parts list however.
The oil pump was still mounted securely. Later I will take it apart and inspect/clean it, but I am rapidly running out of space to store parts, and to have an area to work! I will have to eventually decide which pump one to use, as there are apparently differences between the M70/73 pumps.
After this picture was taken I removed the timing chain tensioner, and the last couple of bolts securing the upper timing case. Rotating the engine on the stand was only possible with my trusty 4foot cheater bar.
This allowed removal of the heads. I noticed that the head bolts on one bank were torx, whilst the other bank was hex. This suggests one of the heads was removed at some point.
My garage floor is now trashed, with oil and coolant everywhere - a cleanup session is definitely in my future!
I can now wheel the block somewhere until I figure out what to do with it. Remove pistons/crank, cleanup and use as a coffee table? (I think I’ve seen that idea somewhere on this board)
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Lots of Oil Dry on the floor and give it a day to pull up all the oil and coolant. After A winter of doing this with my POS Dodge pickup I had to scrub the floor with industrial soap and water to get out the final stains and all of the oil dry dust
Thanks, I’ll pick some of that up tomorrow. I used kitty litter on my last oil spill. Will probably be more effective
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I am assuming you are planning to use M70 heads on M73 block? Do you already have schrick cams on hand?
If not they are NLA and there is absolutely 0 reason to use M70 heads only if you want to decrease performance.
M73 heads are much superior.
Mr Dragon, so in your experience a stock M73 with a chipped M70 DME is superior than a M70/M73 hybrid w/Schrick cams (and of course chipped DME)?
Are you still willing to modify the 2x exhaust manifolds to fit the M73 in the e31 or e32 chassis for a fee?
Have you experimented with increasing the lift and/or duration of the M73 cams?
Thank you very much for your input!!!
The plan is to use the M70 heads, mainly because they’re a plug and play solution, as I won’t need to have my downpipes modified.
As I will be resealing the M73, there isn’t really any more work involved in bolting a hybrid together.
I understand that the M73 heads use roller rockers, and a less failure prone oiling system, but after I’ve used either lock washers or banjo wire to mitigate that eventuality, I’m not sure that there is a performance disadvantage to using the M70 heads.
From what I’ve been able to read, the stock cam profile, combustion chamber size, and valve size are either the same, or very similar between M70 and M73.
Plus, I may have a lead on some Cams.
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M73 Heads are superior to M70 heads period.
With schrick cams M70 heads will produce a bit more power with a tune.
But Schrick cams are NLA...
Any competent exhaust shop should be able to modify the exhaust manifolds..
Too much hassle to ship manifolds back and forth from EU..especially with covid shipping times.
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For one guy in his garage, rebuilding his first engine, the path of least resistance is the M70 heads. I’d like to make more power, sure, but I have what I need on hand to put this engine back together, without having to have anything extra fabricated.
I do appreciate your advice, as someone who has experience rebuilding these v12s. Your build thread from a few years ago was one of the main reasons I decided to attempt this in the first place!
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@ OP
I just had my engine installed back into the car this past weekend. Decided to go all stock, no modifications, no hybrids...just keeping it simple with a replacement M70 motor and new seals/gaskets everywhere. I took the opportunity to have these components rebuilt or replaced knowing that they will eventually fail and will cause me lots of pain and agony depending how difficult it is to access them:
1: Starter
2: Alternator
3: A/C compressor
Love your project, progress, and sharing on here.
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