Hello, there a lot of talk about stock LT1 valve springs causing the lack of power above 5200 RPM.
What makes a higher performance spring better than a stock spring. It seems to me that the spring only closes the valve, maybe im missing somthing here.
Im looking to do the springs and 1.6 RR's in the future.
I just want a good explanation on what the valve spring does.
Thanks

 

Yes, the valvespring closes the valve. They also control the valve, and at higher RPMs, the soft factory springs can't control the valve near as well as a stiffer spring...this is where valve float comes into play. Valve float occurs at high RPMs when the valve spring can't close the valve quick enough. This causes the valve to stay open longer than the cam lobe prescribes. This can cause a loss of power, and in extreme cases, can cause the piston to his the valve and cause serious internal damage. In short, anytime you are turning high RPMs or running an aggressive cam, you need to upgrade the valve spring. Also, valve springs are only 'good' to so much valve lift. Springs are rated to a given valve lift...you want to make sure you have a valve spring rated in excess of the max valve lift.

 

Well said, makes perfect sense.
So for some comp 1.6RR, what springs do you guys to have on stock heads and what do they normally cost.
Thanks

 

Stock springs on 132k mile motor just went 12.50 with just headers and weight reduction, see sig but did feel like we might be loosing some above 5500 so I just put in some LT4 springs, that should get the job done.

 

You want the LT4 spring, retainers, and locks. You can find the part#'s on shoebox's website. They are a great deal. Perfect if you are switching to 1.6 RR's because they work great and are inexpensive.

Dan

 

Valvefloat can also occur at valve close when the valve closes fast and the weak spring can't keep it closed and it bounces off the seat. Some dragracing classes take advantage of valve float and actually design the valvetrain to throw the lifter off the lobe to gain lift without having a high lift cam, the closing side of the lobe has to be designed right for landing though and this is not a street applicable thing just a point of interest.
The LT1 springs were weak because lifting against them is work the engine must do, plus more pressure would be more wear on parts, so GM wanted to minimize the amount of energy taken to lift the valve and the weak on part hence a light spring, the aluminum head springs weren't that bad new but fact is today they are flat out old and valvesprings do lose tension with use and age.