In 2005 Gen IV engines were introduced with now recognizable performance icons like the LS3, L98 and the awesome LS7. A couple of things that could trip up the average engine shop is that some of these engines came from the factory with variable valve timing (VVT) and/or active fuel management. So do your research when building a stroker engine for a customer and make sure you know what you are dealing with. Gen IV blocks came in four sizes 96mm ( and truck), (LS2, LS98 and trucks), (LS3, L92 and L99) and for the LS7. Stroke selection remained the same as the Gen III with 83mm and 92mm, plus the addition of a stroke for the LS7. Another LS block from GM worth mentioning is the aftermarket LSX iron block with a raised cam and deck height that accepts bores and strokes to 108mm x (? x ?). These blocks are capable of handling 2,500 hp with the proper rotating assembly, cylinder heads and power adder. So with a better understanding of the different LS engines produced by the factory, let’s take a look at stroking them for more performance. We contacted Horace Mast of Mast Motorsports for some advice as his company is dedicated solely to engineering and supplying complete LS engines to the aftermarket. His best advice is limiting the stroke to (?) in any standard deck height LS block. (Horace says that most of his engines end up with a ? deck height after surfacing.) This will provide up to 416 cid for an LS3 and 427 cid in an LS7. He has built LS3 and LS7s with ? stroke cranks, but says that the have poor long-term durability, and he doesn’t recommend them, especially for daily driven street cars.