An RB26 head gasket has to suit two things: the size of your pistons and the compression your engine builder is aiming for. This guide covers gasket bore and thickness, the metal gasket types we list, and head studs against the factory head bolts.
Gasket bore: 87 or 88 mm
Match the gasket bore to your pistons. Tomei makes its RB26DETT metal head gasket in two bores. It lists the 87.0 mm gasket for standard 86.0 mm pistons and its own 86.5 mm pistons, and the 88.0 mm gasket for standard pistons and its 87.0 mm and 87.5 mm pistons. Cometic, a gasket maker, recommends a gasket bore slightly larger than the cylinder bore. If you aren't sure which pistons are in your engine, ask your engine builder before you order.
Tomei Head Gasket RB26DETT 87.0-1.2mm 1321870123 | Tomei Head Gasket RB26DETT 87.0-1.5mm 1321870153 | Tomei Head Gasket RB26DETT 87.0-1.8mm 1321870183 | Tomei Head Gasket RB26DETT 88.0-1.2mm 1321880123 | Tomei Head Gasket RB26DETT 88.0-1.5mm 1321880153
Thickness and compression
Tomei lists 1.2, 1.5 and 1.8 mm in the 87.0 mm bore, and 1.2 and 1.5 mm in the 88.0 mm bore. Nitto lists its RB26/RB30 gasket at 1.2, 1.5 and 1.8 mm. Tomei's sample tables and Cometic both show that a thicker gasket lowers static compression, and so does a larger gasket bore. Those tables are calculated, and Tomei says the compression ratio must be set from measurements of the actual engine. Agree the thickness with your engine builder once the block, head and pistons have been measured.
Metal gasket types
Each maker seals the bore its own way. Keep to what each one lists:
- Tomei: a stainless steel "Super Grommet" gasket, with a bead and a metal grommet sealing each bore, and the oil gallery orifice included.
- Nitto: a multi-layer metal gasket with a bead seal and a stainless "O-ring" around each bore, and an HR-200 coating. Nitto gaskets are built to order in Australia.
- HKS: a 1.2 mm grommet-type gasket.
- Bullet Race: a fire ring kit with beryllium copper fire rings and a copper outer gasket, 1.2 mm thick.
Which type suits your block, head and power target is a question for your engine builder.
Nitto RB26/RB30 Head Gaskets - R32-R34 GT-R | HKS RB26 grommet head gasket, 1.2mm | RB26-30 Fire Ring Head Gasket kit
Tomei gasket combination kits
If the head is coming off, Tomei also sells the head gasket as a combination kit with the throttle, intake manifold and exhaust manifold gaskets and the oil gallery orifice. The kits come in the same bore and thickness choices as the head gaskets.
Tomei Gasket Combination RB26DETT 87.0-1.2mm 133013 | Tomei Gasket Combination RB26DETT 87.0-1.5mm 133014 | Tomei Gasket Combination RB26DETT 87.0-1.8mm 133015 | Tomei Gasket Combination RB26DETT 88.0-1.2mm 133017 | Tomei Gasket Combination RB26DETT 88.0-1.5mm 133018
Head studs or factory head bolts
Tomei says the factory RB26 head bolts are tightened into their plastic region, so once stretched they don't return to their original length. Its head studs are designed to work in the elastic range, so they can be used again through repeated assembly while the engine is being machined and built. ARP, a fastener maker, says studs help align the head and gasket and give more accurate, consistent clamping. Tomei's set 193003 has 14 studs and 14 nuts, M12 x 1.5. HKS lists its Head Stud Kit Pro for the R32, R33 and R34 GT-R. Tomei also makes a main stud set for the bottom end. Follow the maker's tightening procedure, and have a competent engine builder fit them.
Tomei Head Studs Set RB26DETT 193003 | HKS Head Stud Kit Pro - R32-R34 GT-R | Tomei Main Studs Set RB26DETT/RB25DE(T)/RB20DE(T) 193013
Ordering
These parts are ordered in for you. Tomei and HKS parts come from Japan and usually take 1 to 2 weeks at the minimum. Nitto gaskets are built to order in Australia, so we confirm the timing with your quote. Email us or use the contact form with your piston size and the thickness your engine builder wants, and we'll confirm fitment before you pay.
Related guides
RB26 rebuild parts list | RB26 2.8 stroker or stay 2.6? | RB26 cams | RB26 timing belt | RB26 running hot? Cylinder 6
FAQ
Is a 1.5 mm RB26 head gasket better than a 1.2 mm one?
Neither is better on its own. A thicker gasket gives lower static compression, so the right one depends on your pistons, your head and block machining and your build. Your engine builder works it out from measurements of your engine.
Will an 88 mm head gasket fit a standard-bore RB26?
Tomei lists its 88.0 mm gasket for standard 86.0 mm pistons as well as its own oversize pistons. The larger gasket bore lowers compression slightly, so check with your engine builder before you choose it.
Can RB26 head studs be used again?
ARP says studs can be reused if they were installed and tightened correctly and aren't damaged. Replace any stud or nut with galled or corroded threads, and follow the maker's instructions each time.