What are the effects of fitting the composite head gaskets to a 3.5/3.9 litre engine?

The benefit of using composite head gaskets on early engines that originally had shim steel gaskets is they seal much better, especially if you are refitting heads without machining the face first, or if there are imperfections in your engine block surface.

With every engine, new head bolts are always required, otherwise damage can occur in the block threads and the torque setting will relax to allow your fresh gaskets to leak again.

The other issue is that composite gaskets will have the effect of lowering your compression ratio, and, although this may or may not be a problem it is worth mentioning. The compression loss is about 0.6.

The third and final thing to be aware of is that the tappet pre-load will be affected, however this is easily taken care of by installing our shim kit.

Engine gaskets and other components can be found in our Engine and Components section of our eBay shop.