How high are you turning with KB Hypers?

I ran a set in my old 366 for 13 years and shifted at 6400/6500 for all those years,,,,motor's still running in a friend's car.

Twist mine to 6500 regularly in my 408 with no issues so far. Although they are related, it's not the rpm as much as it is the piston speed that you have to worry about.

I've spun them 65-6700 in my Slant with spray.

I noticed that even with the 3.91 bore 3.55 stroke the little aluminum rod 341 rev'ed a lot quicker than a lot of old "conventional" 4.04 bore, 3.31 stroke, "real" 340's I've had, I think it's not only piston speed it's ring drag associated with that piston speed as well. I had intentionally limited the powerband to 6500 with the use of a semi-mild hydraulic roller but it got there so quick it always seemed the bottom end was willing to go a lot higher....I just wanted to know HOW HIGH was 'safe'

Thanks guys, now instead of selling it I'm thinking hard about keeping it as a hot little back-up motor and using a slightly smaller solid roller in it to tweak her to go 7400 or so

Being an aluminum rod motor but only turning 6500 I kept the quench around .042, but spinning it up another thou I need to go to a little thicker HG to allow (~.055) for stretch.

I checked with some local roundy round dirt trackers around here that are turning right at 8

I turn mine at 74-7500 all the time. Been doing that for 10+ years now.

apples/oranges, but a good friend of mine with a 406 shivvie ran his to 7000 plus for TEN YEARS! i don't know how many thousands of runs, but iirc, his cranking compression at the end was ~110 pounds? it didn't die- he retired it. still ran great (hard to believe).