Turbo / exhaust studs tensile strength

[csd_19]

Does anyone know what tensile strength the OE turbo/manifold bolts are? 8.8?

I assume that replacing these bolts with 8.8 high tensile studding will not cause any issues - I'm planning to run loctited studs with nuts and nordlocks on the topside of the mani. I'm sure Bill mentioned this on his hybrid k03 thread I just couldn't find the post.

 

[csd_19]

Anyone??

 

[Ronin225]

8.8 is not overly high in tensile strength but i would expect to be fine
Is there any special loctite you will use as i would expect the heat to burn it off
Would it not be best to do up then get it warm up and cool then retorque?

 

[bendohhh]

We use 8.8 grade bolts on loads of the machines at work which go under far more strain than a cars manifold ever would so even if they're not 8.8 as standard I'd guess they'd be perfectly adequate.

 

[csd_19]

I mentioned the 8.8 grade studding as it is the same grade as bolts supplied with some aftermarket manifolds It's easier to get 8.8 than 10.9 studding but they are both available, just wondered what the stock bolts were. I was sure I'd seen higher temp rated locking compound, but like you say it'll more than likely burn off in the heat.

Thanks for the replies fellas

 

[Ronin225]

Just out of interest why are you changing to studs instead of bolts?

 

[csd_19]

They keep backing out - never been happy since moving to a high-flow manifold and changing the bolts at the time. Made the mistake of getting stainless steel 10.9 bolts Seeing as I'll need to rip the 'king manifold off to replace the bolts anyway, I figured going to studs could help things.

What a crappy design where you need to remove the manifold to take the bolts out!

Time for proper manifold and turbo!

 

[Ronin225]

Since you were using stainless it wasnt that the thermal expansion rates were different causing this??
I have heard about studs snapping though more than bolts and studs are 2x cost of bolts

 

[csd_19]

Yep it was indeed the thermal differences that have been causing the issues, hence what I said about making a mistake with stainless

Might rethink the studding idea then, although I've not heard of studs snapping in normal use, but when the DP is unbolted from the turbo

Or just go back to normal bolts lol.

 

[Damoegan]

I've used 10.9 mild steel (black) bolts in the past on a mani with no problems..

 

[csd_19]

I've used 10.9 mild steel (black) bolts in the past on a mani with no problems..

Hmmm this sounds like a winner, just got the joys of swapping the bolts out again... oh dear....

 

[ibizacupra]

nordlocks used?

 

[Damoegan]

Right PITA on a k03/s

You can get OEM turbo to down pipe studs from any dealer

Nordlock's are great too

 

[csd_19]

Yep nordlocks used Bill.

Total PITA!

Will the OEM turbo-downpipe studs be long enough to go turbo-mani though? Hi flow mani installed.

 

[ibizacupra]

are you torquing them up cold then again when its hot?

 

[csd_19]

Yes retorquing when hot - I think I'll replace the bolts again with "normal" ones and see what happens then.

Only want to get it sorted for the MOT in November then take the bloody thing off the road for a while!

 

[csd_19]

are you torquing them up cold then again when its hot?

Bill

Is it normal to retorque the mani-head nuts again when the car is hot?

Swapped from the crappy "high-flow my arse" manifold back to the stock one, what a joy it is to install compared to the aftermarket junk! Removed manifold appears to be warped along the head flange.

Installed new nuts on the studs, and replaced the three turbo-mani bolts along with some new nordlock washers.

 

[ibizacupra]

I tighten then when hot to be sure they are tight...
the aftermarket mani's which have thick block collector, expand a lot more, and stretch the bolts..

tensile bolts wont be tensile after they live in 900'c temps remember..

 

[csd_19]

Thanks Bill

Just the usual 25Nm on the head-mani nuts?

 

[ibizacupra]

I do em by feel.... not a specific number.. you can feel when they're not tightening but stretching..