Tightening the exhaust manifold to downpipes?

[Adnan]

Hi,

A question about M30 exhaust tightening - Bentley says to torque the nuts holding the manifold to the downpipe to just a few inch-pounds and then backing off 1.5 turns. Is this correct?!?

Perhaps the idea is to allow room for expansion when it gets hot since there is no gasket there, just a flare-type fit. Somehow, it makes me nervous.

Thoughts?

Thanks,
Adnan

[Bill R.]

threads with copper antiseize then tighten the nuts to 7lbs which compresses the springs completely then you back off 1.5 turns which takes the springs out of coil bind and allows the exhaust to shift around as needed but still keeping it tight to the manifold... If you use the new locking nuts as specified then it shouldn't be a problem to keep them from backing off, plus the springs always keep tension on the nuts also..

Hi,

A question about M30 exhaust tightening - Bentley says to torque the nuts holding the manifold to the downpipe to just a few inch-pounds and then backing off 1.5 turns. Is this correct?!?

Perhaps the idea is to allow room for expansion when it gets hot since there is no gasket there, just a flare-type fit. Somehow, it makes me nervous.

Thoughts?

Thanks,
Adnan

[Craig]

Those long skinny studs are extremely fragile and will break easily. Trust me, you don't want that to happen. Tighten them down with a 3/8 driver to make sure you aren't putting too much pressure on them and use new nuts.

It's much better to have them too loose than too tight, as it's easy to tighten them up if they are too loose. I've broken TWO of them by being too aggressive while putting the car back together, don't make the same mistake.

[winfred]

threads with copper antiseize then tighten the nuts to 7lbs which compresses the springs completely then you back off 1.5 turns which takes the springs out of coil bind and allows the exhaust to shift around as needed but still keeping it tight to the manifold... If you use the new locking nuts as specified then it shouldn't be a problem to keep them from backing off, plus the springs always keep tension on the nuts also..

[Adnan]

Hi,

Thanks for the clarification, I didn't realize that the springs would compress with such little torque. It makes sense now, tighten nuts till the springs bottom out and then give them a little room.

I bought a set of sixteen copper nuts to cover both the manifold/head connection as well as the downpipes. Just to be safe, I also have all the studs (Murphy's Law).

Regards,
Adnan

[winfred]

the nuts are slightly squashed so they don't spin freely. the 4 long studs just about take the hand of god to remove, i toss the manifold with the broken one and grab another from the yard with intact studs and only go down the long and painful road of extraction if no good used ones are avalable in my salvage yard

Hi,

Thanks for the clarification, I didn't realize that the springs would compress with such little torque. It makes sense now, tighten nuts till the springs bottom out and then give them a little room.

I bought a set of sixteen copper nuts to cover both the manifold/head connection as well as the downpipes. Just to be safe, I also have all the studs (Murphy's Law).

Regards,
Adnan

[Adnan]

the nuts are slightly squashed so they don't spin freely. the 4 long studs just about take the hand of god to remove, i toss the manifold with the broken one and grab another from the yard with intact studs and only go down the long and painful road of extraction if no good used ones are avalable in my salvage yard

[Martin in Bellevue]

No petite studs to shear from the exhaust manifolds?

Are we happy with the driving experience around town? Are things holding together well? Should I?

[Craig]

Are we happy with the driving experience around town? Are things holding together well? Should I?

Do you really need me to answer that?