Tweet
A few data sets I've received indicate about 1.52:1 at the lash point and they actually essentially achieve 1.7:1 a peak lift with a 0.3" lobe (L-72 cam) and slightly less for a lower lobe. These compare to 1.37:1 at the lash point for SBs and only 1.44:1 with the same 0.3" lobe at peak lift.
Given that the L-72 lobe (same one used on both sides and this lobe is also used on the LT-1 cam inlet side) has a clearance ramp .012" high, a cold clearance (iron heads) of no more than .018" is indicated. For aluminum heads I would subtract .002". Head expansion will loosen the clearance about this much at operating temperature.
The "L-72 cam" was used on all SHP BB from '65 to '69 and LS-6, but there were two versions - early to '66 with the grooved rear journal, and '67-up with no groove. The first published clearance for '65 L-78 was .020"/.024". This was increased to .024'/.028" in 1966. Don't ask me why. I don't know.
Duke
Given that the L-72 lobe (same one used on both sides and this lobe is also used on the LT-1 cam inlet side) has a clearance ramp .012" high, a cold clearance (iron heads) of no more than .018" is indicated. For aluminum heads I would subtract .002". Head expansion will loosen the clearance about this much at operating temperature.
The "L-72 cam" was used on all SHP BB from '65 to '69 and LS-6, but there were two versions - early to '66 with the grooved rear journal, and '67-up with no groove. The first published clearance for '65 L-78 was .020"/.024". This was increased to .024'/.028" in 1966. Don't ask me why. I don't know.
Duke