Pure Stock Drag Racing tips & tricks

[Chevy454]

Ok, Marlin, I just got off the phone with both Crane and Comp Cams, and here is what I found out:

Crane Blueprint Cam (1970-1 LT-1):
Part# - 969551
Grind# - 3972182
Gross lift (int./ex.) - .459"/.485"
Duration (@ .050", int./ex.) - 242/254
LSA - 116
LCA - 110
Notes - 1 , 2

Comp Cam (your current cam):
Part# - 12-511-5
Grind# - CS 272 TLS-6
Gross lift (int./ex.) - .510"/.530"
Duration (@ .050", int./ex.) - 242/250
LSA - 106
LCA - 106
Notes - 1 , 2

Now, some observations. What jumps out at me first, and what I questioned above, was the LSA difference between the 2 cams. The original cam had an LSA of 116, which should have a little "lope" to the idle, yet still have plenty of vacuum. Your current cam, on the other hand, has an LSA of 106...this is extrememly tight, even for a race cam! The Comp unit should provide a VERY lopey idle, and would be poor in the vacuum department. I asked both Comp and Crane about that 106 LSA, and they both said "no way" for a street car, and that with that tight of an LSA that you would have little or no vacuum and it would be a dog on the low end. But, what confuses me is that you said the idle is fine and you have plenty of vacuum? The Comp unit is clearly directed at top end, which would be fine if you are looking to race on the skinnies, but it's not necessarily what you were after. The LCA of the Comp unit is advanced 4 degrees ahead of the original, which would help with the bottom end, and all of the other "minute" differences (lift, duration, LCA) would have small effects, but the difference in LSA is what has me confused...am I missing something here fellas? Oh, just curious...did you assemble the engine and put the cam in yourself? Not criticizing, just curious!