Yeah I guess I have a lot to learn. Wish I had known beforehand, but I didn't see much chatter about torquing compound from the threads I researched. I happened to get a tip about lubricating head bolts from an eric the car guy video on torquing heads.
Anyway, I just got a torque angle meter and tested my torque wrench, operating it in similar slipping motions. I found that on a "binding/slipping" event, the wrench would read about 5˚ under the target angle (sometimes down to 3˚ under target). I only had binding once during any single 60˚ turn, so assuming there was one bolt where the fastener jerked once on each 60˚ turn, I'd potentially be under target by as much as 10˚. However, I think that the jerking motion only happened on bolts during the second 60˚ pass. So, would 5-10˚ under target be excusable, or not? Anyone have thoughts?
I would guess you'll probably be fine, hopefully the lack of lubricant on the bolts didn't give you an incorrect initial torque value before you did the angle.
Go ahead and bite. Plenty for everyone.
I'm going to agree with bin on the "you'll probably be fine". But if your really ocd, take it apart and redo it.
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did you use new head bolts?
If the head bolts tightened back up after they got loose, theres probably no damage to the threads and they were just binding, like bin said. If any of them did not tighten back up, id be concerned about thread damage. The V12's head bolts have been known to loosen up and pull out threads from what i've heard/read. You said all the bolts tightened back up so your probably ok.
Last edited by mboor; 05-07-2015 at 10:04 AM.
"**if you suck at driving, it certainly could put you into a curb. Don't suck."
If the final step is angle, they're torque to yield and not reusable.
Go ahead and bite. Plenty for everyone.
Thanks guys. Yes, I replaced head bolts with new. Also, the initial 30Nm torque value went fine. I actually went up in stages: first pass = 10 Nm, second pass = 20 Nm, third pass = 30 Nm with no binding.
Based on what I'm hearing from you, I think I'm going to leave it as is. I am planning on rebuilding the original engine later this year or next to have on standby in storage (assuming the deck is flat and I can get the block's threads repaired properly). I already have the rebuilt heads. After knowing what it takes to get the motor out and all, I'm not so afraid of this car.
I found a small crack in the upper, inner timing chain case (all the way through the casting), and the old one (from original engine) doesn't seem to line up right on the valve cover surface, so I'm waiting on a new housing to come in before I can time it and close everything up.
You don't have to have binding to have inaccurate torque values. The accuracy is all dependent on the lubricant you use on the threads.
Go ahead and bite. Plenty for everyone.
Ok, I've changed my mind about removing the heads; I can't sleep well having not done it right. I ordered new head gaskets and bolts (all Victor Reinz brand, not BMW to save some money...hopefully ok). I'll lube the head bolt threads this time around as well as using the torque angle gauge in conjunction with my torque wrench's angle feature to double check things. Any advice pro or con?
I thought you had left it alone. You probably would be fine for many tens of thousands of miles even with the potential torque inaccuracy. It's amazing how imprecise you can be with car parts that will still give active service for ages. I wasn't criticizing so much to get you to take it apart as to get you to do it the right way the next time.
Having said that, doing it over again won't hurt anything, and it's only money.
Run a tap through the head bolt threads as well as oiling the bolts, you'll have smooth torquing like whoa.
Go ahead and bite. Plenty for everyone.
May I add?
Run a tap *CAREFULLY*.
I've seen very, very interesting things in the past. And the OP, with no disrespect intended, seems like he's not tremendously familiar with tools (which is fine - we've all been there).
So I thought that an explicit remark along the lines of 'CAREFUL with taps, you CAN do damage and it's NOT hard and it's NOT fun at all to fix' might not be wasted.
I do have a thread-chaser for cleaning these threads. Not a tap. Taps are too sharp and not exactly the right tool to clean the threads, though they do work. I just hope there isn't much head gasket material to clean up.
'removing a broken tap is not fun at all' may qualify as the understatement of the week, I think.
Last edited by Hueristic; 05-17-2015 at 08:58 PM.
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When answering my questions please use a qualifier if you are not sure.
The more I work on this car the less I respect German engineering.
When you speak in Absolutes you are always wrong!
Semper Fi
I understand what you're saying (and I do have a M10 x 1.5 tap that will fit in the threads), and I would probably use a tap on any other hole for cleaning. I personally don't feel comfortable using a tap here, especially since I do not know what tolerance/thread class of tap that BMW used when tapping the hole (e.g., H1, H2 / 3A, 3B). My guess would be a 3A thread tap and H1 pitch diameter, but who knows... also, I don't know the tolerance/class of my tap and die set. I just don't want to use a tap in the hole and see ANY metal come out. By using a thread chaser, I can clean out the threads without worry of any damage. I also will run an old head bolt down the holes as well as using brake cleaner. I should think that would be adequate when torquing with lubricant, no? This is what I did last time, and the threaded bores looked VERY clean.
This is a worse overthinking than deciding to do the head bolts and gaskets again.
Class Of Thread
There are three established Classes of Thread, designated in the Unified series by adding “A” for screws and “B” for nuts (or other internal threads) to show definite limits and tolerances.
Class lB Thread is that in which a 1 A screw can be run in readily for quick and easy assembly. The hole is classified as 1 B. The fit is 1 B Thread, and rarely used in modern metalworking.
Class 2B Thread consists of a 2A screw in a 2B hole. This 2B Thread has wide application, accommodates plating, finishes, and coating to a limited extent and, therefore, has fair tolerance allowances.
Class 3B Thread means a 3A Screw in a 3B Nut or threaded hole for applications where tolerance limits are close.
GH Numbers
In the tables that follow, tap selections are shown for the Class of Thread desired and, under the Class of Thread heading, applicable GH Numbers are listed. "G” designates Ground Thread. “H” means that pitch diameter is on the high side of basic. These two letters are followed by a numeral showing the tolerance of pitch diameter oversize as follows:
H1 = Basic to Plus 0.0005"
H2 = Basic Plus 0.0005" to Plus 0.0010"
H3 = Basic Plus 0.0010" to Plus 0.0015"
H4 = Basic Plus 0.0015" to Plus 0.0020"
H5 = Basic Plus 0.0020" to Plus 0.0025"
H6 = Basic Plus 0.0025" to Plus 0.0030"
H7 = Basic Plus 0.0030" to Plus 0.0035"
Use a basic tap or an H1 and you'll be fine. Don't be ridiculous and use a tool that isn't the correct tool for the job because you've justified it in your mind.
Go ahead and bite. Plenty for everyone.
I think you hit the nail on the head there; I tend to overthink everything I do in life.
Haven't been updating this thread for a while...I have been working on the 750 off and on, and trying to dodge the absolute torrential rains this season. The most ever here, in fact. You may have heard about the South Carolina floods last month, yep it was serious and it is still affecting a lot of people, many roads are still closed here in Columbia. Some friends of ours down the road lost their house and all vehicles and had to be rescued by boat.
I did get the block threads cleaned up and retorqued on new heads with new bolts and gaskets. (Side note: the instructions included with the gaskets sourced straight from Victor Reinz differ from what BMW TIS says... VR says to do the first torque pass (30Nm), wait 15 minutes, then do the two 60˚ passes. BMW doesn't mention the 15 minute wait time after first torque, though that may be a common knowledge thing among mechanics.) I made sure to put torquing lube on the threads of the bolts as well this time and it went more smoothly.
Redoing Bank 1 head:
Redoing Bank 2 head:
Needed to buy a new upper, inner timing cover. The original engine's timing cover didn't line up right at the top of bank 2 head. The same part on the replacement engine was actually cracked through the case. New part fit fine.
Both heads torqued correctly with new upper timing cover:
Working on timing with the vastly expensive timing blocks:
Valve covers on. Story time: Had to work quickly on these under stress of extreme cloud-to-ground lightning storm. Didn't help that a brand new BMW nut stripped on me while the lightning rained down. Rushed to find a suitable replacement from somewhere to get the covers torqued properly before calling it quits for the night. No pics of all of that haha.
Putting on the intake manifold gaskets:
New ping sensors:
Yes, those intake manifold supports (on the valve covers) are bolted on wrong. I fixed them.
Intake manifolds on:
Accessories going on (so easy with engine on a stand):
The car and the engine:
More updates and pictures to come...
Wow, good to know that you did not abondoned this project
welcome back
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Your current situation is not your final destination
this is amazing, it must be so much easier to work on the m73N with the motor outside.
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I just read through this entire thread, it's awesome to see you a tackle an engine that so many people fear. In fact, it looks simpler than my M62tu! Simpler SOHC heads, and only one timing chain.
Can't wait to see it back in the car!
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