NiftyNiblick

I happened across the specs of my car's original Rochester injected engine.
The so-called Duntov 30/30 solid lifter camshaft, which was to reappear once again in the '69 Camaro Z28, seems outright wierd next to the current engine's hydraulic roller cam.
The valve lifts were less than one might expect to see on a high performance camshaft, but the durations were ludicrously long.

Any valve train experts out there with a possible reason for this?

mikem350

OEM parts need to last under warranty, and higher lifts put more stress on all the valvetrain parts. Higher lifter wear, wiped cam lobes,etc. As technology improved parts and oils and the opening and closing ramps of the lobes, the mfgs were able to go to higher lifts. Longer duration = more horsepower up top, so that was the safer way to get more power.

Roller cams can follow the lobe profiles MUCH more easier than solids...enabling the outrageous profiles for more "area under the curve"

NiftyNiblick

Thanks, mikem350. Going by memory of my teens, the new engine doesn't quite have the cement mixer idle that I remember from fuelies in the old days. It's horsepower still matches up fine, however, while its ft. lbs. figure at useable rpm is vastly improved.

Every Corvette is a "fuelie" now, but mine, which only has a vin plate and a few coachwork parts actually remaining from 1962, remains one after 47 years!

NEVERL8

I am not a valvetrain expert, per se, but I did recently rebuild my 327/350 L79 engine and converted it to a full roller setup.

The roller technology along with the advancement of metallurgy allows you to get much more performance out of a cam while sacrificing far less driveability and durability.

Roller cam and lifters can have much quicker ramp rates than flat tappet lifters. This allows you to open the valve much faster. Since the valve opens faster it can stay open longer (more total area under the curve) allowing for more air/fuel charge into the cylinder (if the intake and heads will support this). The newest metallargy in valve springs allows you to run high seat pressures and high lift. You can now snap the valves shut much more quickly (of course lighter valves, springs and retainers help).

The sum total if you do it right is an engine that has reasonable idle (not horrendous overlap or real narrow lobe centers), decent idle vacuum, runs hard to 6K RPMs all day, makes plenty of power, runs on pump gas, and will last for years and years with regular maintenance.

My next engine will be a solid roller big block. Now that should make some interesting sounds.

knight37128

Springs don't wear out near as fast with a lower lift.

A fresh set of springs will do wonders for high RPMs.

rustylugnuts

If I understand correctly, you have a 1962 fuelie, correct? If so this engine never had the 30-30 duntov camshaft. It had the 097 duntov solid lifter camshaft with very low lift, and a much longer duration then other camshafts that were used in the earlier years.

rustylugnuts