Headgasket Choice

[Morgz32]

hey guys

quick question concerning a headgasket and valve clearance, do i need to use a specific headgasket with a certain thickness for a RB25/30 for valve clearance so pistons dont smash into the valves? pr is there no issues involved with just using a metal headgasket?

cheers

[r33_racer]

Most people just use a 1.2mm headgasket as that is 'the norm' and there usually are no issues involved.

If you are worried about valves hitting pistons then you need to dummy assemble everything and put blue tac/playdoe on the pistons where the valves sit over and torque head down on the hg your going to use and turn it over by hand and check if its hitting. Basically just keep on trimming the stuff down until you have about 2-3mm(80-120thou) clearance I think the number usually is.

Something that might help you out. We once ran our 25/30 with 9.0:1 cp pistons with camshafts @ 10.2mm lift, running a 1.2mm headgasket and we had a tad over 80thou clearance, which had no problems with pistons hitting valves.

On a sidenote you usually dont use the headgasket to increase your piston/valve clearance. You modify the piston if its not a predetermined setup. Which is usually just a case of throwing them in the mill and cutting valve reliefs into the tops

[Morgz32]

Most people just use a 1.2mm headgasket as that is 'the norm' and there usually are no issues involved.

If you are worried about valves hitting pistons then you need to dummy assemble everything and put blue tac/playdoe on the pistons where the valves sit over and torque head down on the hg your going to use and turn it over by hand and check if its hitting. Basically just keep on trimming the stuff down until you have about 2-3mm(80-120thou) clearance I think the number usually is.

Something that might help you out. We once ran our 25/30 with 9.0:1 cp pistons with camshafts @ 10.2mm lift, running a 1.2mm headgasket and we had a tad over 80thou clearance, which had no problems with pistons hitting valves.

On a sidenote you usually dont use the headgasket to increase your piston/valve clearance. You modify the piston if its not a predetermined setup. Which is usually just a case of throwing them in the mill and cutting valve reliefs into the tops

thanks man helps alot im going for the same cp pistons aswell with 260 deg camshafts with 10.25mm lift so if you didnt have a problem then i technically shouldnt, but will use that blue-tack trick sounds like a good idea t make sure

thanks

[D_Stirls]

I think you will have a problem with the 10.25mm of lift if you are keeping the factory hydraulic lifts, i have heard that you have problems with an exposed gallery with anything 9.25mm of lift. I have not seen this personally it's just what i have heard.