Stock Hemi Cam question

Does anyone know what the intended difference in the stock cam for the 70/1 versus the 68/69 was. Spec wise they have the same duration/overlap, but the 68/9 had less lift and manual states at zero lash. Which would imply even less actual lift if lash adjusted to spec. The 70/71 had 490/481 at zero lash and with hyd lifters. Was the cam profile different so that the area of lift was about equal? Or was there a performance improvement in 70. Just curiosity.

Biggest difference was 68-69 was solid lifter and 70 had hyd lifters.

I built Hemi motors for NHRA stock for both the solid lifter 1968/1969 and one 1970 motors. I bought and used after market cheater cams in both motors that would check legal, I did finally check 4 sets of stock rocker arms and found that those rocker arms are way off on the ratio , I saw from .430 net lift to .530 net lift on the same cab lobes on the exhaust rocker and a tiny bit more variances on the intake rockers
Any Mopar V8 motor, especially 426 Hemi motors, like more air and fuel to make more power
On your question are you wanting to buy a stock cam? If so don't
Buy a good after market cam design to work well with your motor and car

It is curiosity. I have 4 stock type cams on a bench. I can measure different lift heights at the cam, plus looked at what service manual, Mopar race manual states. Since there are no numbers on a stock cam just trying to understand what mopar was doing and how to tell the difference. It seems they had 3 cam types for factory stock. The 66-67 mech with lower duration and lift. The 68-69 mech with more duration and lift, and then the 70/71 hyd with same duration as 68/9 but even more lift.

Based on the cam specs I would have thought the 70/71 rated with more HP based on the cam improvement.

The muscle car HP wars where on full time in those days and Mopar was deeply involved in drag racing, I'm sure they wouldn't shoot them selves in the foot by adding HP to a known engine combination making some of their cars move up a class in the new model year cars being sold

So why the change from an engine build perspective. Same exhaust, same intake, same heads, basically same carb with some jet changes. Same distributor. (Understand emission change in 68). But cam lift and duration rose in 3 variations according to service manual data. The book uses zero lash for the lift spec on the mech years. So if you subtract the lash spec, you really have a mild lift in the .440 range. In 70 with hyd no lash you have about .490 lift. So I would assume equal 70 roadrunner would have no problem beating a 69 roadrunner all day.

you could get power brakes with a street hemi and the ones I fooled with had to have the brake booster removed to set the lash. best is map the cams out if you have them. keeping in mind that if your measuring at the lobe the effect of rocker ratio and lash will need to be figured in for the solid and zero lash for the hydraulic may give a big unrealistic number due to ramps.

Valve noise is a perceived quality control issue.
Hydraulic lifters remove that.