XF Exhaust Allan Bolts /

[virden]

Will some kind soul please tell me the torque setting for the Allan bolts that attach the manifold to  a cast iron head.  Why?... cos I have blown yet another middle gasket..Thye only seem to last 1000 miles.

Thanks

[Jonathan Kay]

Deleted

Jonathan

[Gordon C]

Give Vulcan Engineering a ring

 

They supplied some gaskets for me some years ago. Not sure what they are made of but lets just say they have never leaked and thats with removing the primaries a couple of times as well. I can only describe them as a laminated type of material almost asbestos like. Worked for me

[apjenkins]

Chris Wheeler of 'The Seven Workshop' supplied me similar sounding copper/"asbestos" gaskets that were perfect for many miles.  When I reused them I added some 'copper silicone sealant' which never burnt or leaked. Torqued the Allen set screws, with spring washers under the heads to - feels tight enough - tension and checked for tightness after the first few runs.

@ndrew

[Nigel Riches]

Check the face of the flange for flatness. If it's over about 0.5mm out of true have it skimmed and go easy on pulling the bolts tight. 

Nigel 

[Roger King]

As stated, make sure flange is flat, use laminated type gaskets and tighten securely, but not too firmly, using just an allen key so you don't have too much leverage. The final job is to lockwire the allen screws so they can't come undone because, inevitably, the gasket will settle and loosen the screws.

If you overtighten, you will simply collapse the gasket at each end and encourage warping of the flange again.

[elie boone]

Len Selby does a gasket that is 1 piece but far more superior than the OEM part http://www.historicracing.org.uk/parts/garageclearout.html

[virden]

Thanks all, the head is true and I had the flange planed, so not a gap issue. I am wondering if it is a case of the shear weight of the  4:1 and silencer which is providing a leverage to flange  forcing the bottom in an dthe top out.  It is always the top which blows, and I have tried several different types of gasket...but never double.

[SM25T]

Do you use the front mount on the chassis to help support the weight of the system ?

[virden]

SM25, I have heard that there may be a bolt hole in chassis rail but do not know where it is. My car is a 96 S3 live axle,built by Arch

[SM25T]

Ask them for confirmation ? Normally between 800-805mm from the centre of the rear exhaust mount hole ... at the same height from the underside.

[Nigel Riches]

Don't mount any bracketry from chassis to the exhaust system, mount it back to the engine block, so the engine, exhaust, and bracket, all triangulated together move as one piece,. 

Movement  of the engine will transfer energy through the exhaust and then into the chassis / frame, which is not a good situation. 

​Nigel. 

[virden]

Nigel,

If I used a rubber exhaust bobbin as used to attach the rear bracket, would this not mitigate the worst of the vibration?

[Roger King]

If you do that, you'll effectively be using the exhaust as an engine stabiliser which is a no-no. There's no problem with the standard mounting system provided everything is done properly.

[Drumster]

Just for the record, I never had any issue with the gaskets provided by Chris Wheeler on my '93 x/flow. Thus was with a 6" Techcraft silencer and 4-into-1 primaries with a single bobbin on the bracket near the tailpipe.