head bolts torques??

shanon

shanon

Well-Known Member
Messages
2,067
Reaction score
597
Location
NorCal
hello Coupers

Need to know the head bolts torques, hopefully sooner than later......trying to check this off my to-do list today.

Thanks in advance.

-shanon
 
51 +/- 1.4 lb/ft or 7 +/-0.2 mkp

Bolts should tightened in three stages in order of 1-14:

12--8--4--2--6--10--14 front of car
11--7--3--1--5---9--13

The engine should then be warmed to temperature and the cooled before another torguing down. After 600 miles they need to be tightened for the last time
 
Just to by my usual pain in the ass thought I'd bring up the controversy between the specs in the manual and the more conventional thought regarding head bolt torgue. Someone on this list (sorry, don't remember who...again) torqued the head bolts using the degree method and the figure was more in the neighborhood of 75-ish pounds (not the exact number). A few BMW mechanics feel the new higher number is more beneficial in alleviating head warpage. When I built a single cam engine I used the 'new' torque figure (which is written down somewhere - have no idea exactly where that might be, though) and must admit that during the final torquing sequence there was a little sphincter factor goin' on.
 
Also spend the money on new bolts! After 30 odd years and or lots of "haynes" moments (disassembly/assembly) I would treat yourself to some new ones.
Some of the "new" gaskets only require a one time tighten, read any notice/instructions that come with the gasket set!
Malc
 
Malc- not only that, but the head bolts are the "torque to yeild" type, meaning they deform after use, and therefore cannot be reused. ARP studs can be re-used, however.
 
x_atlas0 said:
Malc- not only that, but the head bolts are the "torque to yeild" type, meaning they deform after use, and therefore cannot be reused. ARP studs can be re-used, however.
Click to expand...

I don't believe this is correct. M30 head bolts are not torque to yield. M20, yes. M30, no.
 
Torque to yield or not, I've certainly reused M30 head bolts without problem. I'm pretty sure AndyM is correct.

You do need to be careful with new gasket materials. With these cars you will find new material and NOS material. Hopefully your gasket kit will come with instructions.

I've also heard the opposite advise in regard to tightening - basically that over tightening can lead to warping. IMHO, head warping problems on M30 stems from the sorry radiator design these cars came equipped with when new.

You gotta love this forum. We even have opinions about the valitity of factory specifications. :D
 
jhjacobs said:
You gotta love this forum. We even have opinions about the valitity of factory specifications. :D
Click to expand...

Yep. I actually tried to stay out of this debate -- I use a torque angle gauge for setting the final torque on my head bolts.
 
My thoughts about replacing the bolts was they just get old. Plus if you know the head has been on and off a few times with the same bolts used again and again they start to fatigue.
The nightmare of one snapping, which I have had happen, and the effort required to get the remains out of the block is something I do not want to go through again :roll:

Just a cheap "insurance" policy IMHO
Malc
 
Head bolt controversy

The older bolts were not torque to yield. Nevertheless, the bolts can be deformed even after one use. I have one new bolt that I use to compare the older bolts I "may" reuse with digital caliper. The usual tell-tale sign is stretch. If a bolt is longer than the new "unused" bolt, it gets used for something other than a head.:wink:

Although I have never seen it, some folks claim BMW issued a tech bulletin recommending the angle method for tightening on the M10 and M30 engines. I also have seen instructions with the newer gaskets approve this method. So keep those protractors handy! I am currently clinging to the past with sealed gaskets (made in the early 80's) still sitting on my garage shelf. I overbought. :cry:

To me, a bigger controversy exists whether to coat the gasket with copper spray or leave it naked and clean. (Do not need to be reminded of junction with timing cover.) I have also heard differences of opinion regarding the coating of head bolts with: nothing, motor oil, anti seize, and yes - even some sort of adhesive. I typically go dry, but have dunked bolts in oil with other marques.

HTH
 
Huh. The B35 head bolts are torque to yeild, based on the Bently manual. The original Blue Books don't mention it, but I have heard many times of the head bolts stretching, so like Malc said, cheap insurance.
 
Head Bolt controversy

x_atlas0 said:
Huh. The B35 head bolts are torque to yeild, based on the Bently manual. The original Blue Books don't mention it, but I have heard many times of the head bolts stretching, so like Malc said, cheap insurance.
Click to expand...

I don't , in any way, profess to be an expert in this area, although I have many rebuilt and modified internal combustion engines under my belt. Since I do not have any reference materials handy, I think it fair to say none is error-free. Not that the dealer can't be wrong, but I had seen the dealer "re-use" head bolts when doing valve jobs - back in the day when the newest thing on the block was the E24 Series. As it often does, thinking and technology/metallurgy may have changed and insurance, when inexpensive, is always a good thing.


On a side note, I do not recall the Blue Notebooks mentioning use of a protractor respecting head bolt tightening. Hence, one time torque-to-yield bolts probably were not used then. So too, the Bluebooks rarely instruct replacement of parts and fastener's unless absolutely necessary, e.g., the head gasket.

Again, I would agree that replacing fasteners is good insurance - as is new pistons and wrist pins and rings etc. But that doesn't mean critical parts cannot be reused. I also wonder about reusing bolts to secure critical driveline parts (crankshaft mains, flywheel and clutch), upon which many comprehensive reference materials also remain silent. Of course, some bolts are easier to replace than others.

Just food for thought. :?
 
Re: Head bolt controversy

Snip.......
To me, a bigger controversy exists whether to coat the gasket with copper spray or leave it naked and clean. (Do not need to be reminded of junction with timing cover.) I have also heard differences of opinion regarding the coating of head bolts with: nothing, motor oil, anti seize, and yes - even some sort of adhesive. I typically go dry, but have dunked bolts in oil with other marques.

HTH
Click to expand...
bengal taiga,
I guess we all have our "own" ways of doing things, plus all makes of engines too!
I have rebuilt engines from MG, BMC A series, mini etc, Land Rover, Citroen, Fiat, Lancia, BMW :lol:, Yugo, Jag etc. All seem to say different things about it but my "rule of thumb" is as follows..... Please note this is my way of doing things and is no more valid than other folk's way of doing things!

1)... Everything clean and dry!
2)... clean out threaded holes in the block, ensure a bolt goes to the bottom, If "raggy" run a tap down them
3)... Most modern gaskets appear to be coated with a sealing agent and often have deformable "goo" around the cooling and oil passages. Check instructions about using sealants etc!
4)... Check the bolts and replace if any suspect.
5)... Very lightly oil the threads of thead bolts, using a light machine oil
6)...Very lightly oil the washer or underside of the head bolt.
7)...Follow instructions about tightening
8]... Be smooth and progressive when tightening, no jerks or "just a little more" type snatching!
9)... Get the job done in one go, IE make sure you have everything ready.
10).. Make sure you have a decent torque wrench! You can even get them calibrated for a few quid to check that 50ft-lbs is really 50ft-lbs!!!

I learnt this stuff from my Dad and his life long pal Mr Manors, who used to fix aircraft engines during the 2nd world war. An amazing chap with some really scary stories who though now long gone still influences what I do!
Malc
 
Senor Malc, I could not agree with you more, as a rule of the thumb. I have also had the pleasure of working with and knowing a few long-gone folk with considerable war effort involvements and aircraft industry experience. (A few of these folk were known to throw a caber and wear the Black Watch.)

Their collective knowledge was hard to beat. That said, I fondly remember one such person who had a penchant for being or finding the exception to every rule. :wink: Translation: maybe there are a number of ways to be right!
 
M10 tightening instructions - the same for M30?

I noticed your link to tightening instructions, but the link'd site mentions M10 and M12 engines only. Since I do not have access to the CD, to which you refer, I was wondering if the linked site is just an exemplar of the instructions or is actually the page 12.

I appreciate the effort, and yes, I am aware we are basically referring to 2/3 rds of the same engine.(I do not mean to imply we should use 2/3 torque values!) I have several M10 and M30's in my garage - torqued the old fashioned way by torque wrench alone. I have not had any headgasket issues that I am aware of; however, should the need arise, I will keep a protractor available.

Thanks
 
M10 and M12 in this case refers to 10mm or 12mm bolts, not m10 or m12 engines. The info is directly copied from the factory CD [print screen]
Hope this clears it up!
 
You must log in or register to reply here.
Back
Top