Re: Correct 1970 LT1 Camshaft....
Sometimes these "specs" go through multiple filters and sometimes the filter doesn't know squat about camshafts or an error is made. After dealing with about a dozen OE lobe's detailed engineering data I know that errors are easy to introduce when dealing with hundreds of five digit numbers that I had to type into Excel to do my dynamic analyses of the OE cam lobes. The GM drawings list lobe lift to five decimal places every degree of cam rotation.
The gross valve lift of the LT-1 cam at 1.5:1 rocker ratio is .459/.485".
Valve lift, net of the clearance ramps at 1.5:1 is .441/.455, so it looks like they took one from column A and one from column B.
If you want to verify that the CS1145R is really the OE LT-1 cam you can measure the "heel to toe" dimension, which is the peak of the lobe to the base circle, with a caliper.
Heel to toe = base circle diameter + gross lobe lift
The following are nominal dimensions from the GM blueprints rounded to three decimal places:
Inlet: 1.202 + .306 = 1.508
Exhaust: 1.202 + .323 = 1.525
If your measurements vary more than a couple of thou from the above, get back to me.
As I've stated before, the LT-1 cam inlet lobe is from the L-72 cam, but with a smaller base circle. The L-72 lobe base circle radius is .63857/.64057".
The exhaust lobe is from the 30-30 cam with the same base circle.
Duke
Sometimes these "specs" go through multiple filters and sometimes the filter doesn't know squat about camshafts or an error is made. After dealing with about a dozen OE lobe's detailed engineering data I know that errors are easy to introduce when dealing with hundreds of five digit numbers that I had to type into Excel to do my dynamic analyses of the OE cam lobes. The GM drawings list lobe lift to five decimal places every degree of cam rotation.
The gross valve lift of the LT-1 cam at 1.5:1 rocker ratio is .459/.485".
Valve lift, net of the clearance ramps at 1.5:1 is .441/.455, so it looks like they took one from column A and one from column B.
If you want to verify that the CS1145R is really the OE LT-1 cam you can measure the "heel to toe" dimension, which is the peak of the lobe to the base circle, with a caliper.
Heel to toe = base circle diameter + gross lobe lift
The following are nominal dimensions from the GM blueprints rounded to three decimal places:
Inlet: 1.202 + .306 = 1.508
Exhaust: 1.202 + .323 = 1.525
If your measurements vary more than a couple of thou from the above, get back to me.
As I've stated before, the LT-1 cam inlet lobe is from the L-72 cam, but with a smaller base circle. The L-72 lobe base circle radius is .63857/.64057".
The exhaust lobe is from the 30-30 cam with the same base circle.
Duke
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