Philia_Bear;40319 wroteNo offense to you but you should do some more research into the modular engine
The difference in compression is from the difference in the shape of the pistons, the squish and quench area's are the same and the volume is the same (or within the 2CC of tolerance of my measurement)
No idea who your talking to for a re-builder but the valve seats are machined the same unless they have been worked on by some muppet at some point
For reference I rebuild Volvo heads on a daily or weekly basis and have 4 S40/V40 (2 turbo and 2 NA) heads sitting in-front of me at the moment for comparison
1 each of -99 and one each of 2000- (some minor things change in 2000 like vvt etc)
Side note.... you should note what year the head is as not all B4204s heads are the same as noted above
When I get a chance I'll take a photo of my B4204S head and my B4204T head and you'll see the difference. Just for your reference, the bore and stoke for the pistons of the B4204S and B4204T are the same so that only leaves the difference in combustion chamber.
Volvo VIDA also lists different part numbers for each head as well as some of the internals and both are non-VVT.
Either way this isn't meant to be a technical discussion. The B4204S head is the head I'm selling and it's off a 98 S40. If someone wants to use it on a turbo engine, that's their business.