yeah, compression has a big part in this as does a great tune. but id say no more than 10-12 on a good tune but id stick with the latter. they have an exellent stroke to rod ratio of all the b series motors. but oem limitations are exactly that limits. i run a b20 thin ass sleeve block on 8 psi tunned by scotty at mainstream and made 258.71 whp and have recently bumped to 10psi again and have run this set up for over 4 years now. but like i said i got 8:8:1 compression too! all engines have a service life, some short some long...