Reading about Mexican blocks: despite what some have said of them, they're no stronger in construction than US ones, probably stemming from their use in a lot of trucks... and the assumption made that they're somehow a heavy-duty casting. The iron is apparently not as wear-resistant, meaning bores wear out more quickly. Re: Boss blocks. They were essentially a tunnel-port block with 4V Clevo heads. Forged crank, 3/8" big-end bolts, The tunnel-port was a sad episode in engine failures. The ports were so extreme, that the motor had to scream upwards of 8500 rpm to make the numbers. The port runners were circular and so big that the corresponding pushrod had to go down the centre of it, running through a tube pressed into the head. Sort of like like the port entry from a red motor, albeit round, not rectangular. Sent from my CPH1607 using Tapatalk