212 hemi
- Thread starter bikelife35
- Start date
- Tags 212 hemi
Lift has little to do with valve clearance during overlap. Duration and lobe center determine how far the valve is open near TDC. When valve is at max lift it is nowhere near the piston. Exhaust is the more critical one as the piston is chasing the closing exhaust valve and if there is any float they could collide. I just build a hemi with a BM jr and .310 lift and 1 to 1 rockers it has no clearance issues but with 1.2 to 1 rockers you need to check. I used 37 lb springs cause the JR needs a bit more spring than the regular BM.
It is a black mamba jr but in his website you can get it with various lifts under the custom cam section, I got it as a 230 duration with .310 lift so I guess I am confusing people by saying it is a jr but it basically is with faster and higher lift ramps. For the 47 lb single springs I got from isky they are wider and require the spring pockets cut. I bought the cutter Isky sells then found it cut a 1 inch seat which was hitting some side protrusions in the head. I chucked it in the lathe and with a toolpost grinder narrowed the cutter from one inch to around .900 but I am going from memory and lately it is not too reliable.
If I had gone with the 246 degree duration and .310 lift I could have used 26 lb springs and not had the hassle of cutting the seat. When I did that motor the only ratio rockers for the hemi was brad hills (200$) and if figured it was easier and cheaper to just go hi lift. But the seat cutter cost $100 so maybe it was foolish economy. I also had to clearance the block slightly. Now NR and arc sell the i.2 roller rockers for 99 bucks.