Looking for new valve springs to cure my valve float on my mild hydraulic roller. Phone jockeys at big cam companies are useless, so need to educate myself. Can you offer advice on any of the following..

1. Generally, how many pounds is it safe to shim a valve spring to boost seat pressure?

2. When shimming to increase seat pressure, does it also increase the open pressure?

3. When increasing the spring pressure, is it common to upgrade from a "street" to a performance valve so the stems don't tulip/ deform/ break?

4. When increasing spring pressure, does going to a longer valve/ taller installed height reduce stress on the valvetrain because of a lower spring RATE.

5. When do you need to switch to a billet cam or billet lifter bodies, when increasing spring pressures?

6. What is more critical..open pressure or spring rate re question #5?

7. What spring manufacturers to avoid? I am thinking about Comp or Manley springs as my choice.


I did lots of research when assembling the motor and consulted both Comp cams and AFR, and actually went slightly stiffer than what they recommended. The springs were removed and checked before assembling the engine. My current K-motion springs are 125 pounds on the seat with an installed height of 1.8" and 305 pounds open, with a rate of 325 pounds. The cam makes peak power at 6000-6100rpm, so I want to shift about 6200-6300rpm. When the springs were new, valve float happened right about 6100rpm. After a few months it sometmes happens around 5900. I do have a rev kit in it, but I beleive the 12-14 lbs of boost I am running necessitates a higher seat pressure, that people do not take into account. I need to find at least 300 more rpm. I beleive I need a spring with 140-145 pounds on the seat and 330-350 pounds open, along with titanium retainers.
I called Comp and asked for the part numbers for the retainers, etc for the 918 beehive. Both Comp and AFR suggested against the beehives but would not explain why. The Comp technician kept pushing the 986 and 987 springs, but both the 986 comp spring that the cam calls for as well as the heavier 987 spring are either lighter or no different than what I have in there now, so it doesn't make sense to me.

If you look on some of the cam manufactuers sites, most will tell you 150 pounds on the seat is about the most you can run before starting to collapse a hydraulic lifter. They also state that about 350-400 pounds open pressure is the max recommended for a cast hydraulic roller cam...ie. Crane's site: "*Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads."

http://www.cranecams.com/?show=howToSelect

My heads were bought directly from AFR with quality stainless steel valves. On 2 different calls, 2 different technicians told me I need to upgrade the valves when going to a heavier spring. Thus my questions about the need to upgrade springs and going to billet when going to a heavier spring.

I have identified several springs as potential candidates, but each has its own caveats. I noticed Comp just introduced the 26120 beehive springs that have the perfect 1.445" diameter to fit my AFR valve pockets, unlike the 918 beehives. However, the specs on the 26120 beehive is 155lbs on the seat at 1.88" installed height, 377lbs open and a spring rate of 370lbs, thus my concerns noted above re. the warnings from the supposed experts. Wadda I know.

I don't think the aftermarket vendors have the technology down yet and I get lots of bad advice, mixed with the occassional good, so that is my challenge.. but I will get it figured out eventually, though

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1973 RS Z28: Littlefield race series 6-71 supercharger on a 355 w/ AFR 195 heads, 10-12 lbs boost, 7.6:1 static compression, CompCams hydraulic roller (276/288 advertised, 224/236 @.050 duration, .510/.527 lift w/ 1.52 rockers on a 113 lobe separation), AFR Hydra-Rev kit, Eagle 4340 Forged Steel crankshaft, ARP studded bottom end, Eagle ESP H-beam rods, TRW forged reverse dome pistons, Comp Pro-Magnum 1.52 roller rockers with 7/16 studs, twin 750 Edelbrock carbs, 1&3/4 inch Hooker Super Comps, 3" dual exhaust with cross over pipe. MSD 6AL ignition & Pro-billet distributor, Tremec TKO-500 5-speed, Moser 12 bolt with Eaton posi, 33 spline axles & 3.42 gears.

 

I would highly suggest the 987-16 spring. Chances are that the KMotion spring you are using now is the 1.25 diameter single spring designed for flat tappet circle track applications. If so it was never intended for street use with a hydraulic roller. Hydraulic rollers have more valvetrain inertia and are more difficult to control. Beehive springs are by nature a single only design with no dampner and are engineered to work within a spcific ramp profile window. Valvetrains go through many hamonic ranges and one size does not fit all. Raising seat pressure also raises open pressure by a like amount. You raise seat pressure to raise the open pressure. Coil bind needs to be foremost on your mind when setting up the springs. Once a spring experiences valve float it will remember the abuse and pay you back with ever decreasing rpm before it happens. The H11 material used by K-Motion for that spring can be unforgiving and may very well break when overstressed. Please consider that the cam manufactuers are professionals and generally know what they are talking about. Give them all of the information and they will lead you down the right path.
If you have one piece stainless valves now then there is no reason to upgrade materials unless it was a marine application with sustained high loads. Then the exhaust valve might be worth looking at.
There should be no reason to consider more than 135 lbs on the seat for a hydraulic roller cam.

Good luck!