compression with 274cam

I ran a 284 extreme in my old 360 with 10.4 compression. I only had 10 inches of vacuum though with 155-165 cranking psi. I also had clearance issues with the retainer to valve seals on a set of 308 heads. I eventually just ground the crap out of them with a 2inch grinding disc and cleaned them really well. Also I used a set of crane single springs with the new cam and was running close to coil bind with it; not on all just some because of production differences. One more thing I busted two of those springs within 16 months but very very very lucky neither of the valves dropped.