Exhaust manifold studs - Recommened torque setting?

[mk1storm]

Hi,

I've fitted exhaust manifold studs to my RV8 as a) they're probably more robust anyway and b) the threads in the head were a little suspect and wasn't too happy about getting a good clamping force with bolts.

However, I'm not sure what torque I should tighten the nuts up to. I believe if you're using bolts then the torque is 15Ibft but I should be able to go higher than this with studs I assume (unless there's no need).

Is anyone else using exh studs and if so what torque settings have you used?

Ta...

[sidecar]

Hi,

I've fitted exhaust manifold studs to my RV8 as a) they're probably more robust anyway and b) the threads in the head were a little suspect and wasn't too happy about getting a good clamping force with bolts.

However, I'm not sure what torque I should tighten the nuts up to. I believe if you're using bolts then the torque is 15Ibft but I should be able to go higher than this with studs I assume (unless there's no need).

Is anyone else using exh studs and if so what torque settings have you used?

Ta...

I made a load of studs for my engine as I hate ali threads, ones that get red hot are just asking for trouble!

I must admit that I did not use any torque rating though. I used two nuts locked together to wind in the studs, the final nuts that were used were just done up with a spanner 'quite tight' but not 'mega tight'

[mk1storm]

Yeah fair enough.... I think I'll aim for 20Lbft, but if I feel it's more than about half a standard arm full then I'll relax it...

A well calibrated arm full is usually fairly reliable

[spend]

I use studs on the lower manifold flanges and put an extra locknut on which also keeps the thread clean. Cheap 12 pt aircraft nuts seem to work fine and hell of a lot easier than the LR lock tabs.

[topcatcustom]

A nut done up on a thread should provide more clamping force than a bolt done up to the same torque anyway, so you may find that the same torque rating still slightly improves the clamping anyway, on stuff like that I just go by feel with a spanner or ratchet.

[SuperV8]

What is the thread of the nut?

The head is a corse thread and I'm guessing the nut will be standard to fine thread which means even at the same spanner torque there would be more pre-load under the nut.

I would "nip it up" then re check once started and maybe "re-nip it up"!

Tom.

[mk1storm]

SuperV8, yeah good point. The thread is finer on the outer portion of the stud so yes it would have higher clamping force for the same torque.

In the end as you guys have said I just went with my feeling. I did use the torque wrench to take the torque up equally in stages. Ended up with 35Nm in the end. Seemed about right. Could have gone more but didn't think there was any need.