Volvo started putting in the "K" sometime in 88-90, never got an exact date (heard a bunch of different ones!)

This is called the "K block" and is the result of volvo realizing they had it right back in 84 with the B23F.

The B230F block (prior to the "K") had somewhat (still strong though) weaker components compared to a B23F.

So in essense, the B230F "K" is built like a B23F, however if memory serves correctly, it still retains the smaller main bearing journals of the non-"K" B230F... But this is not really an issue. It does have the stronger rods and a few other components important to handling [fairly insane amounts for a stock block] quantities of power

I've heard of much success in building up B230F "K" motors, and that they really aren't any weaker than the B23F in reality... and the B23F is pretty much accepted as the strongest block put in the 240's.

Stronger than stock? the "K" block *is* stock. just a good type of stock:)

Enjoy, and make sure you do all the required things before you start playing around with that wastegate ... I'd hate to see a "detonated and threw a rod" message with your name on it anytime soon. IE: Do your routine maint., make sure you've got PLENTY of fuel to dump in, and check your timing!

Get a fuel mixture gauge (the type that attaches to the O2 sensor will do) so you can see if you lean out. If you lean out, get off that gas [quick!]and ask yourself why you're not dumping in enough fuel.

Autometer makes on of these for like $60 (check carparts.com or the like) that easily mounts in your dashboard (remove one of the black plastic filler panels, there's a 2 1/16" hole behind it;)) ... super-inexpensive insurance for your fuel system and everything that depends on it. Plus the back-and-forth action indicates your O2 sensor is working right, and can be more entertaining to watch than a LONG red light.

Cheers,
-Nate