composite head gaskets

[arthuy]

Hi,

I have been spending the weekend under the bonnest of the old V8. If it weren't for those pesky rusted and siezed bolts I would have been finished yeaterday.

Any way, I had ordered up some new gaskets and decided go for comp over tin.

It occured to me that I don't know what the torque settings are for the comp gaskets. I have torqued to 55ftlb which I reckon could be about right as the tin should be 65-70 ftlb.

Does anyone know what the torque settings should be for comp gaskets?

Colin

 

[chrisyork]

Head nut torque should not be affected by gasket type. ie continue to use 70lb ft for the 10 main bolts and 20lb ft plus a locknut for bolts 11 to 14. (These latter 4 are ommitted on later engines and there is a school of thought that encourages binning them on our age of V8 as well on the grounds that they tend to distort the head.) PS no matter what it says in your version of the manual do the 10 main studs to completion first and only after tackle the remaining 4.

The point of torquing down nuts/bolts/studs is to induce stretch in the bolt or stud thus giving a force to pull the two surfaces together. We need this because setting off a load of petrol air mixture in the cylinder is inclined to force them apart! Unless your planning on dropping the compression ratio and / or driving on half throttle you still need the same pull on the head studs!

Which brings me on to compression ratio. The composite gaskets are slightly thicker than the metal ones. They therefore reduce the compression ratio by a factor of approximately 0.6 to 1. This is brilliant news if you have a 10.5 to 1 engine - you might get rid of your pinking problems! Bit of a curates egg for lower compression engines - depends on your personal taste. You'll get a softer running more accomodating engine but also slightly less power and worse fuel consumption.

Chris York

 

[arthuy]

Hi Chris and thanks for the reply,

I wasn't sure because with my 2200 the torque is 55 ftlb for steel and 70 ft lb for the composite ones.

I also broke a bolt a few months ago with standard steel gaskets so I am a bit weary of the heads for now.

Colin

 

[02GF74]

Hi Chris and thanks for the reply,

I wasn't sure because with my 2200 the torque is 55 ftlb for steel and 70 ft lb for the composite ones.

I also broke a bolt a few months ago with standard steel gaskets so I am a bit weary of the heads for now.

Colin

.... like what chris said. I recently fitted a pair of heads and used the steel gaskets. I did not fit the 4 outer bolts at all, this does leave the bolt holes open but so what?

If you snapped a bolt, then maybe it is time to replace the set? They should only be used 3 times max. Before fitting the bolts you should clean out the bolt holes either by running through a tap or an old bolt with a slot cut in it.