heads

how restrictve is the heads on the gta turbo not that im getting it done its just that i need to know as much as possible about tuning these etc

Cams and exhaust manifolds need rectifying, long before the heads need modifications.

The feedback I got from the Aussie PRV6 brigade ( who have some seriously modified versions) was that the porting is very bad and that to make big power they need major modification. I suppose it depends how far you wanted to go, the turbos don't need head work to make 260 - 270 bhp and the atmos can make 220 -230 with the usual polishing porting and valve size increases - along with other mods obviously.

..ahh, but they are mainly talking about the Volvo heads, which have crap ports. They prefer to use Peugeot or Renault heads.

After stripping both an R25V6 Turbo and Volvo B280E motors recently, I found the Renault had much better ports, both had similar combustion chambers, with the Volvo having bigger valves and approx 1.5mm more lift at the lobe on the cams. The conrods were identical.

All the conrods on all of the PRVs are the same (even fire) whether it be turbo or normally aspirated. Best heads are the Laguna/Safrane normally aspirated by far. Older PRV's (V6 Turbo, Volvo etc) have a port diameter that goes down to 40mm, Laguna has 46mm minimum, and the largest inlet and exhaust valves of the bunch.

After stripping both an R25V6 Turbo and Volvo B280E motors recently, I found the Renault had much better ports, both had similar combustion chambers, with the Volvo having bigger valves and approx 1.5mm more lift at the lobe on the cams. The conrods were identical.

Have you checked the rocker ratio on both engines.?..even though the cams may have more lift, it may not be more at the valve..

The rockers are identical as far as I can see. Same casting marks and adjusters, but saying that I have not measured the lift at the valve on both heads. The turbo cams are tiny, and the valve springs on both engines are very similar and have very little tension on the valve. I will be putting in some heavier springs in the rebuild.