The Lister Petter LPW series parts manual lists three different thicknesses for head gaskets. The thickness of the head gasket is identified by small holes punched in the external corner of the gasket.
Lister Petter has discontinued all but one of the head gaskets and there is only one thickness head gasket available as service parts. We have had a number of customers become very concerned they are not replacing the exact gasket that was originally in their engine. Again the replacement head gasket will work in all engines. There has been significant speculation why there were multiple head gaskets. Obviously, they were made to adjust for manufacturing tolerances. Best guess is there were multiple thickness to make sure the engines would pass emissions within the manufacturing tolerances. Slightly lower compression in diesels can result in increased unburned hydrocarbon emissions and soot. So to make sure all engines would pass emission certification and they would not have to scrap parts if the tolerances were off slightly multiple head gaskets developed and were installed as needed at the factory in new engines.
There are also discussions around the reuse of head bolts on these engines. The factory manual does recommend replacing the bolts but the head bolts are reusable as they are not torque to yield bolts. We have reused head bolts in our shop in many engines with no head gasket issues. Obviously head bolts with excessive corrosion or other visible defects should not be reused. There are also two types of head bolts in these engines. There are head bolts for all non-turbo engines and there are head bolts for Turbo charged engines. The “Turbo” bolts are higher strength and can be used in naturally aspirated engines, but be aware a set of Turbo bolts currently runs over $400 if you want to make this upgrade.
We get requests for head torque specs. Here is the head bolt torque and tightening diagram. Follow the instructions and your top end job should be completely successful.
Also be aware there are differences between the upper and lower push rod tube seals. It is recommended to always replace these seals when the head is off because the head must removed to replace them if they leak and head removal means you have to replaced the head gasket. Head gaskets in these engines are NOT reusable once they have been torqued.
There are a couple of other things to know when replacing a head on these engines and we will create other posts on those topics.