So our 300 hp L28 with the 44mm carbs, pistons and other nice bits from the original BSR 240 running at 13:1 CR on 110 fuel ran hot from day one. The 240 did real well at the VRG event last year taking 1st, 2nd (overheating on the last lap), and DNF (first lap overheated). We changed out radiators, hoses, timing, a new head gasket, reconfigured the cooling system, replaced the BSR E31 head, etc. Little bubbles became much bigger bubbles once the throttle was blipped. Current thought is a small cylinder wall crack. Since the only thing that didn't get changed was the block and we started to get bubbles at idle and then big bubbles at WOT. We figured cracked block. Out came the engine and all the usable stuff (8-gal custom oil pan, diesel water pump and custom front cover, a real BSR valve cover, the huey tranny oil cooler