Race Engine Forum UK

When I built my engine (1978 Lancia Beta 2000 using a modified VX head with appropriate holes plugged) I tightened the carrier to head bolts to 16lb/ft, left them overnight for the gaskets to settle and then re-torqued them again to 16lb/ft.

After a short 15 mile test drive I found one serious and a couple of minor oil leaks. Once the engine was cold I found most of the carrier bolts had slackened off to around 10lbft, 45-60deg was needed to get them back to 16.

The bolts are plated 12.9 socket head caps of uncertain provenance (i.e. new, but ones I had lying around). I'm wondering if 16lbft just wasn't putting enough tension into them and whether I'd be better off with 4.6 or 8.8.

I've experimented with an old head and found that I could get up to the mid 40s before the threads in the head started to fail so I've now re-torqued all the bolts to 20lbft.

Questions:
Is 16 lbft the correct torque?
Do you recommend loctite or similar on these bolts?
Should I be using a lower grade?

Many thanks,
Stuart

Did you check the mating surfaces before fitting?
You should have used NEW bolts, old bolts may have already been tightened beyond their yield stress, not too sure what spec the bolts are, im sure Guy will reply to your post soon and advise you more correctly what to do.
Regards
Steve

Yes.
The bolts were new - see original post.

12.9 M8's should be around 27 ft-lbs, depending on lubrication, what plating, etc. They'll certainly loosen at 20.

I'd go with lower grade bolt, there's no need for the high clamp.

Hi Jason,

We'll see. I've replaced them all with OE 8.8 at 22lbft. As soon as I get a chance (Good grief...the rain....) I'll take it out and see what happens

Stuart

Hi!


I usually torque up these bolts `by hand`- have never experienced them "slipping" back - so I have no comment on this.

Though:
- In my experience - depending on gasket type and head/carrier mating face condition - slight use of some sort of sealant (silicone or other) usually sorts the problem.....
- I have also used the wrong gaskets once resulting in serious oil leaks. as reversed new head/old style head differ slightly.....easy to mix up if You have several gaskets lying around.
- I suppose You have the right cam boxes? - never done that myself but suppose I could have....
- Are You sure the oil is not coming from the cam covers? Oil coming from there tend to "pool" around the carrier gasket and it often looks like a leaking cambox - especially after a drive when You open the bonnet and discover an oil leak. This is actually more common than a leaking cambox.....

I just cannot see that the bolts in itself would present this problem - but I have learned to be VERY humble regarding engines - the most weird things can happen:-)

BTW: Be sure to double check cam/valve clearance when finished.....

Frustrating - yes!! - but probably no big deal - Good luck with the engine:-)

Keep us posted.


Remi

The torque setting for joints should be determined according to the shear strength of the female thread. In this case aluminium alloy and the GC recommended spec is 14-16lbf ft (ie: 15).

The question of bolt grade is rather immaterial, 12.9 grade can be used but on the other hand 12.9 grade must never be plated because of the danger of hydrogen embrittlement. Plain black 12.9 is ok as is 8.8 grade (incl zinc plated stainless which I use). The underhead region should be oiled and the threads lightly coated in copper-based anti-seize. Definitely no thread locking compounds!

That is my regime and it works. I allow overnight for settlement and don't thereafter have a problem. Of course there is a bit of 'bedding-in' and settlement after running but never a huge amount.

I wonder if your torque wrench is the problem here? Cheap ones are notoriously inaccurate, I would only use Snap-On or Facom.

GC

Another thing to keep in mind here is that at these lower torque settings, you'll want a smaller torque wrench with a 1/4 or 3/8 head. The 1/2 head ones usually are built for higher torque ranges and even the a-brand ones are inaccurate at such low settings.