i have no doubt i seen the answer but can't find it again. i've seen in heaps of threads that 13-14psi is about the limit on these engines. what exactly needs to be dont to realiable put more boost in say 20 psi. Can it be done or is it to much.
do a search theres a few people that have run 20, they go very well but if you want to do it reliable go build a new block and make it a 4 bolt main.
SD's are only 3 bolt and like to snap cranks, this is why you only see up to the 14 pound mark anymore then that and you risk having a 2 piece crank