What RPM will the valves float on a 100% stock valve train, 1970-71 426 Hemi? Thanks.

Are we talking a fresh build to oem spec or something that had a handful of valves parked open for 3 decades?

Really more details would help. I've seen many stock rebuilds on almost anything result in less performance than original so many variables to consider.

No personal experience with an original hemi but through my reading/research, I don't think there were usually many issues with valvetrain instability on these within the usable rpm range of the engine.

Several things affect the valve float RPM, the tach, the amount of lifter preload, the lifter quality and the valve springs
i race a 1970 426 Cuda in NHRA stock for 2 1/2 years back in the early to mid 1970s, I had help a couple race a 1968 or 1969 hemi GTX the year before and the valve spring pressures where almost the same on those two motors, we would shift both of them right at 7000 RPM. The GTX had a Sun electric tach, I had a expensive electric Auto Meter tach in the Cuda which read 6200 RPM when it would nose over hard, I ended up adding a Jones Motorola mechanical tach in 1975 and found out that the Autometer read right at 1000 RPM less above 5000 RPM than the mechanical tach did so I threw it away. I saw the same thing later on another SB car I helped on, the electric tach read low in comparison to a tach drive tach above 4000 RPM
As far as your deal shift it when it quits pulling hard, don't wait for it to start popping and backfiring before shifting

I have seen the designed maximum speed 6800 rpm a few times, one source is the interview with Pete Hagenbuch at Allpar:

https://www.allpar.com/threads/inte...nt-leader-part-3.229378/#post-1085223476

The lifters will stop first before valve float. Why, are you racing it?

The answer depends o if you’re talking about original factory built motors “back in the day”, or something like a survivor with some real mileage on it, and valve springs that have probably lost a little something in the last 50 years, or a “restored” build, built as close to factory specs as possible, using current production “equivalent” parts.

The primary cause of concern for me on the resto-build would be the hyd lifters actually being as good as what came in a new hemi.

https://www.moparaction.com/2020/05/23/1970-plymouth-hemi-gtx-road-test/

Thanks for all the replys. I don't own one. I am just very interested in how 1970-71 hydraulic valve Hemi ran in stock form back in the day. I am impressed at how high the RPM was until valve float. I am also curious of what was the common shift point RPM for these stock 1970-71 Hemis, and would the stock cam be the limiting factor of the shift point? Thanks.