LS-1st-Gen

Im curious, especially since Ive just beome the victim of this phenomenon. I know it's because the piston will smack a valve before it closes fully, by why is this happening in the 1st place?? Can the LS1 valvetrain just not keep up with the bottom end at high RPMs?? IS this problem inherent in any pushrod engine, due to the excessive amount of valvetrain components that slow down the engine internally? Whats the deal??

-Gordon

Wicked ls 1

Could have been valve float from overreving down shifting to soon,not having hardened pushrods, or could be like me and snap a timing chain.

unit213

Personally, I haven't heard of anyone bending a pushrod who didn't miss a gear or overspin the motor by downshifting into the wrong gear.

MOBE

Me neither.

Its not a flaw in the design. Its more often than not, driver error.

For the record... I've never bent a pushrod.

Danny2tek

iTrader: (1)

missed a shift maybe?

dlandsvZ28

It's happening because of weak stock valve springs.

Install aftermarket stronger valve springs and it's likely to stop valve float and/or bent push rods, etc. That's why you can raise the shift points, and the rev limits when you upgrade the springs and valve train components.

blk~2000~Z28

This is true but will do nothing for a missed shift or wrong gear that will cause the motor to spin to the moon. The springs and hardened push rods are only good to a limit, go over that and the same thing will happen.

unit213

Now you did it. You shouldn't have said that...

MOBE

Nah. I broke a valve spring instead.

BlackEcho

iTrader: (1)

just go out and buy an A4. no more worries--

B-MAN

If you are running nitrous and you miss shift say goodnight to your pushrods unless they are hardened or chrmolly.

crewdawg16

Of course aftermarket springs are only good to a certain limit, but that limit is better than stock, that is the whole point. Especially with the titanium retainers, less weight = quicker reaction. If you wind the hell out of the motor, past the stock rev-limiter, you are gonna float a valve. Plain and simple.

Cal

iTrader: (1)

Maybe going back to basics would help here . . . in most engines, the valves are mechanically forced open, but when it comes time to close them, they rely on springs to pull them closed. These springs can only close the valves so fast no mater what the rpm is. The speed they get closed is based on spring stiffness and valve train mass. So at some high rpm, the springs are no longer able to get the valves closed in time, and in extreme cases the piston hits the valve. Some exotic engines use "Desmodonic" valves. In this type of valve train, the valves are both opened and closed mechanically, so you don't have this problem.