the Official 16v thread

**Preen59** · 02-08-2008, 09:32 PM

Originally Posted by Valver.

You can see that the exhaust side is basically exiting at a 90deg angle, but then if you open it up too much, you lose a lot of bottom end... stuck either way really. The sharp-cornered lip just off the valve seat can be smoothed right over within reason, but it's quite hard when the head isn't in two pieces like the one above!! I can't speak from experience - never done one myself, just had the process explained to me to just a big expense (!) - but they say it's a very hard head to work on, which is easy to see with the cross section pics.

Other problem is that the exhaust valve is too big in relation to the intake valve (according to theory anyway), which is why you go up 2mm to 34mm on the intake, but only up .5mm to 28.5mm on the exhaust when going to bigger valves

Yeah bonk made that comment about the exhaust, but from what i understand he's done what he can to improve that within reason. He's removed all the lips etc and once the seats are cut he'll finish it off properly.

What comp ratio did you run with your ibiza?

I'm thinking 11:1 for mine, but i'd like to get some input from people who have used the same engine.