I plan on rebuilding my 1970 SP 350 at some point. Don't plan on anything wild just a nice street motor, 325-350 HP. Advertised compression of 10.25 is considerably less so I have read in other posts. I have seen a recommendation of removing .020 from the heads and using the .020 head gasket to bump compression on the non high compression 350s but no recommendations for the SP motors. Wondering if using this same formula on the SP motor will be okay? And at what point would someone need to consider using adjustable push rods?
I milled the heads & used steel shim gaskets on my last one to get to 10.5. Was many years ago and don't remember the specifics or if I actually checked but w/stock pushrods/rockers & KB C118 it seemed to be fine. I'm sure there's a methodology to checking it.
When you assemble it, check the push rods. Are the ones that are closed still have some slack in them? I don't know what the actual spec would be, but I'd want at least .020"-.030" left over. If a lifter has .100 total movement in the plunger, I'd ideally want half of that when the valve is closed. With new parts like cam, lifters, rockers and shafts, things are liable to snugger than the pre-rebuild engine had. If they are too tight, you can break the rocker shafts or worse. My brother, back in the early 80s, had too little clearance and broke rocker shafts. Instead of buying shorter push rods, he used steel soda can pieces under the rocker pedestals as shims. It ran like that for many years.
