IME(experience), Factory 340 springs could barely do the job in the first place. Every 340 I ever had, OK all 4 of the factory 340s and one DartSport 360 I ever had, floated the valves waay too early; one of them barely made 5500. And two of the four were low mileage engines when I got them, including the lowest at 11,000miles.
I put those 340 springs on my teeners and get 5500 or better out of them. I got a big ol' box full of them.
I know, 4 or 5 engines don't sound like much, but for me it was 100% failure.
A Hi-C factory 340 is just woke up at 5500, and with an automatic, needs to hit 6200 to 6400 to cover the powerband, and I like to stretch 'em out some more than that, just to put a little jump in the hood on the shift.
I put some Hughes 1111 springs on my HE3037AL, and now she goes 7200 or better all day,every day,and has for over 100,000 mi.
Don't wimp out on the springs. Don't wimp out on the oiling mods. Don't botch the cam-install, and Don't forget to straighten out the rocker geometry. Then drive the berrys off it!
I had an HE2430Al for a few years. That's a little 223/230/110 Hughes. The power peaked at 5000 maybe a little better. With my powerband requirement,I only needed to spin it to 5500. But you know with those springs and the Eddies, that stoopid little cam just kept pulling like the Energizer Bunny. So I let it buck, sometimes to 7200, cuz it went there! What a rush for a guy that was used to 340s calving early.
Hyup wind it up in first, slam it into second, and burn the tires till the little red-light comes on! Then on the brakes real hard, cuZ you know, a speeding ticket eats into my gas-money.
I'd give up my beer money for a month, to get good springs. Oh wait, I don't drink beer.
I'd give my condom-cash for a year, to get good springs. Oh wait, my wife is 60.
I'd give up um,lessee, a rev-limiter, for good springs. There ya go.
