When upping the boost on a standard type engine , sometimes its a good idea to pull the compression back a little bit. This can be done easily with a thicker headgasket as one way of doing it without having your pistons machined. Going thicker in headgasket size is only a solution for a certain amount , if you end off needing a ludicrously thick gasket to get the compression you want then its probably time to start thinking about other options. The problem when you go too thick on the head gasket can be reliability. This area at the very top of the cylinder is where a lot of the really high pressure energy is made – its often a weak point on some engines prior to increasing the thickness. Increasing the thickness increases the surface area the chamber sees pressure over , meaning that the gas can now actually get more force into blowing the gasket out.
If building your engine from the onset for really high boost then we would recommend you ask about piston machining being involved in your build. If you maybe already have you engine built but are having some slight detonation issues then the RnD gasket could be ideal for you. Usually the heavier detonation on a z20 will always be around the outer ring of the piston , usually around the exhaust valve side.
The z20 engine tends to have quite a tight squish band . The standard tolerance of piston protrusion is 0.4mm , its acceptable to skim the block a few thou so piston protrusions can easily get into the 0.45mm area without piston correction. The standard headgasket is 1.1mm thick , the cylinder head is flat and has no recess for the piston. This leaves us with an area around the top of the piston that will come within 0.65mm of the head ( about 0.025" ) just turning the engine over by hand , a little closer maybe at 7000RPM . The RnD gasket is 1.6mm thick , this immediately bumps 0.5mm onto this size giving us 1.15mm ( about 0.045 ) - this size is certainly better for running more boost , if you have built a few engines for high boost then you will maybe still also think that this is still tight!
The 1.6 mm gasket is the thickest gasket we recommend for the Z20 engines for high boost reliability..
The RnD gasket has no rivets installed - do not mix up the gasket layers
We also offer custom machining of z20 pistons via post
Custom machining on pistons available on new pistons £95 inc VAT set of 4 pistons.
We also have some developed Wossner Pistons arriving into 2020 , please get in touch if you are unsure what you need
We strongly recommend the use of ARP headstuds , we only use this in all our engines.