Just curious in case I keep the 341 as a back up motor, I can put the 255/263 @.050 solid cam i just swapped out of the 414 back in (which was the original plan). I'm thinking I'd like to try a well ported high velocity set of 318 '302' closed chamber iron heads with a 1.88 or 1.94 intake just to be different.

I've heard of guys turning high 6000's low 7's with the KB's just wondering how far anyone has pushed them I planned on turning about 6600 with the E-heads.

I was running a set to 7600 on a 340... a rod let go
after about 1 1/2 seasons...so it wasnt a piston failure

That's great to know mr P, thanks!!

One option i have with this 3.55" stroke, 6" rod rotating assembly is you get to swap it all into a 340 block by just changing the slugs... interestingly the KB 340 flat-top is listed at the same 507 grams as the kb167 318 I have in the 341; that would be cool to swap it all into a 370-ish inch 340 motor and not even have to rebalance

7400 sounds good to me

Don't make any assumptions based on KB's published weights. They seem to list a standard weight for a bunch of different pistons.

That's true but the 167' were right at 507, I wouls suspect a larger and similar compression height 340 would be (if anything) a little heavier. so long as I could theoretically get the piston/pin combo to weigh the same it would be golden.

I once missed a shift and the playback tach said 9000 Ended up spinning a rod, but the pistons were ok..

I ran kb 107 hyper flat tops to 7300 all the time on a 3.58 stroke / 6.123 rod, never thought about the pistons but worried about the cast crank

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).