Originally Posted by
nevsrevs
You can get a thicker gasket for the rs too, can't remember the part number, they were made for frs that have been decked or skimmed, as for the head 400 is ok on standard ports and valves, maybe above that you would want work on valve throats.
That's probably the ST gasket, it's a four layer rather than the standard three layer (0.40 vs 0.27 IIRC). I know that Pumaspeed sell them as an 'upgrade'
Sure you can make 400 on the standard head (people have got alot more than that too) but it's a restriction at that level.