Just installed a custom speced boost cam from tsp with tsp cnc heads decked 5 thou with standard PAC 660 springs and retainers. Cam spec is 635/635 227/239 on a 115lsa, vvt is locked at zero. Standard ls7 lifters and ls2 trays, I do have tsp LT roller rockers increasing my ratio to 1.82 over the standard 1.8. I measured pushrod length using the comp cams 7702 tool. I have 50 thou preload on intake and 70 thou on exhaust, and ended up with 7.825 push rod length. My question is with the rocker ratio change putting my lift at 641.9 am I getting piston to valve under high load or am I losing control of the spring because of the increased weight of the roller rocker? I asked texas speed and they said I should have no issues but looked at a cam from cam motion with similar lift and slightly different duration and it requires pistons with bigger valve reliefs or knotching or (flycutting) of factory piston. I've double checked my exhaust and motor mounts, haven't found anything loose. Verified knock is still there with e85 and is rpm related.
Car only has 18 degrees of timing in it and me and my tuner both agree to not add anymore until the knock is sorted. I will add I removed baffles inside my valve cover because I found the roller rockers hitting the valve cover but can no longer find witness marks on the valve cover. Consulted with tuner and got my valve events from texas speed and adjusted soi and eoi tables accordingly to the cam. Any feedback is appreciated. Fixing to switch back to stock rockers with che trunions and see if the roller rockers are my problem. Just seeing if anyone else ran into this issue before.
I found on a c6 forum where someone had a similar issue after 6000 and his btr 660 springs couldn't handle the weight of the roller rockers at redline, swapped to stock rockers and never had another issue.
Any suggestions or feedback is appreciated.
