Hi. could anyone advise me on the pro's and cons of using a newer 8v cross flow head as opposed to the older MK1/ MK2 heads. will they fit a 2E bottom end? many thanks
They can be made to fit, but they don't fit properly without machining on the head face, I believe. VR6Will did one
Will is the expert on these, I dont think that there is any power gains to had from the head other than its easier for a TB or carb conversion.
In theory it should make more power, as the inlet gases won't be so overheated by the exhaust ports & manifold... the ports are also less restricted in shape. In practice... not enough people have done it to be sure. Will built a really high spec engine, but didn't push the compression ratio enough to make the power he wanted... got 170ish bhp and about the same lbft torque. With 12.5 or 13:1 compression it could have been more, but you have to match the CR to the cams. With a 300 degree cam, big valves, good porting, and a big squeeze, you should get close to 200bhp. No use in a road car though. You'll need to spin it pretty fast to get the power though, with a lairy cam, so the bottom end needs to be balanced and properly sorted. At the end of the day, it'll be easier to make the same power from a 2.0 16v or a 1.8T, as you've got more valve area.
like for like the x-flow head should flow better than the counter flow head. 7mm valve stems for starters help matters mine needed plenty more mapping and higher compression to achieve what i was after! they fit pretty easy
