why is it so difficult to understand quality matters

[grumpyvette]

I recently had a guy ask me what valve spring he should use on his rebuilt corvette hydraulic roller cam, engine.
I strongly suggested he discuss the choice of valve springs with the cam manufacturer, and NOT JUST TAKE MY WORD or ANY ONES WORD, but too DO SOME RESEARCH ON THE ISSUE! and not to select the least expensive parts he could locate, and to always ask if there was any thing to be gained or potential problems that might occur if better springs were installed
now anyone with a functional brain cell should realize that if your given a choice between two different valve spring sets and one set cost $40 and a different set costs $240 that theres got to be a few differences in quality because no vendor is going to stay in business selling $40 springs for $240 available some place else for $40, theres always a reason, and its up to the purchaser to ask questions
it should be rather obvious that you can,t compare directly cheaper OEM valve springs with better aftermarket springs and that the more expensive springs allow greater valve lifts and more clearance, and frequently are designed too use smaller lighter weight retainers
yeah! you may have guessed he at first selected the dirt cheap factory replacement springs and even though they worked he felt that the engine should pull a bit harder, so after several discussions the topic of the correct valve train geometry and valve springs was re-discussed and the decision was made to (TRY to do things correctly, and BEHOLD THERE WAS AN IMPROVEMENT! AMAZING
heres an example of two totally different valve springs that were used on the same heads and "amazingly" the more expensive springs and lighter retainers added about 800rpm to the engines power curve.....its amazing to some people that theres differences in quality but trust me THERE IS and you tend to get what you pay for!, if you ever wonder why some guys have an engine that can pull 6500rpm when a very similar engine seems to get into valve control issues at about 5700rpm, theres a reason

Part# PAC-1283
Weight 73.00 grams
Large End I.D. 0.845
Large End O.D. 1.25
InstallLoad 110.0
Install Height 1.750
Open Load 328.0
Open Height 1.150
Coil Bind Max 1.080
Lift Max 0.600
Frequency Base 33960
$240
http://www.racingsprings.com/Store/Prod ... ductID=213
http://www.racingsprings.com/ShoppingCa ... p?Buffer=1



Part Number:
12495494
Brand:
GM Performance Parts
SKU: 12495494
$40
This GM Performance Parts high performance Single Valve Spring has an outer diameter of 1.32". The kit includes 16 P/N 12551483 valve springs. This spring was originally used on 1996 LT4 Corvette Small Block Chevrolet engines.



Technical Note: Not recommended for cam lift over .525".
LT4 SB Chevrolet Valve Spring Kit (12495494) Specifications
Coil Bind (in.): 1.220
Installed Height (in.): 101 lbs. @ 1.780
Outside Diameter (in.): 1.32
http://sdparts.com/details/gm-performan ... s/12495494


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WATCH THE VIDEO
http://howautowork.com/part_1/ch_1/valve_spring_22.html

 

[Indycars]

I searched the internet and here and I don't find anything on the term "Frequency Base". Is this just the Natural Frequency of the spring ???

 

[grumpyvette]

obviously the cam lobe design and taking the time to get the correct clearances, rocker geometry and spring installed height are mandatory for getting any valve spring to perform correctly and in the case above I strongly suspect the cheaper springs were, just dropped in place and the retainers and keepers installed with zero checking on those factors and when it failed to function as expected,only then were the checks made,as I expect has been the case in thousands of valve spring swaps I have no idea as to what hydraulic roller cam was used, but it was slightly more agreasive than the (HOT CAM) the newer springs were installed TO SPECIFICATIONS, after he had issues, with all the valve train checks on those factors being done as he didn,t want to go thru the process a third time.
like most of us we tend to learn from our mistakes or from those of close friends and whats required to correct them, rather than doing the required research up front

Valve Spring Tech
Valve Spring Pocket Clearance

Valve spring pocket clearance is the gap between the inside diameter of the valve spring pocket (or cup, if used) and the outside diameter of the valve spring.

Too much clearance will result in the spring "dancing" around in the head, which "beats up" the spring mounting surface and the spring itself. If this is the case, a spring cup may be used. Additional machining of the spring pocket may be required to accept the spring cup.
Not enough clearance will bind the spring in the pocket, over-stressing the bottom coil by limiting its movement and not allowing the spring to "grow". This will cause the bottom coil to wear against the head and/or prematurely fail. Machine the valve pocket using a Spring Seat Cutter if not enough clearance exists.

Valve Spring Retainer Fit

The valve spring retainer should fit the valve spring being used. A slightly snug fit is acceptable, however a fit that is too tight can overstress the top coil, and cause it to fail. A fit that is too loose can lead to spring "dancing."
Valve Spring Installed Height

The installed height of the valve spring is the distance between the valve pocket (or cup, or shims) and the outer edge of the spring retainer (which is the height of the valve spring) when the valve is closed. To check installed height, follow the following procedure:

Install the valve in the guide.
Install the retainer and valve locks.
Install all spring cups and/or valve spring shims (basically, everything except the valve spring).
Hold the valve closed by pulling the retainer up tightly against the valve locks.
Measure the distance between the outside edge of the valve spring retainer and the spring seat. A snap gage or a height micrometer should be used.
Check the distance against what is recommended on the camshaft specification card. An installed height of +/- 0.020" is acceptable.
If the installed height is not within 0.020", either machining of the valve pocket, or removal/installation of valve spring shims is necessary.
Repeat this procedure for the rest of the valves.

Valve Spring Retainer to Valve Seal Clearance

The distance between the innermost step on the valve spring retainer and the valve guide must be 0.090" larger than the maximum valve lift of the camshaft. Measure the distance between the top of the valve seal to the bottom of the valve spring retainer. After adding 0.090" to your measurement, it should still be larger than the maximum valve lift of the camshaft. If not, machining of the valve guide in necessary for adequate clearance.
Valve Spring Coil Clearance

Coil clearance is the distance between the valve spring coils when the valve is it maximum lift (fully open). A minimum of 0.060" must exist between the coils at maximum lift. Coil bind is when the valve spring is compressed fully-to the point that all of the coils are "stacked up" on top of each other. For high RPM applications, .100" is recommended . Coil bind is a catastrophic condition that will result in valve train failure. Disassemble each spring (if multiple springs are employed at each valve). Check all the springs (both inner, and outer springs) If there is not 0.060" - 0.100" minimum of clearance between the coils, the solutions are: the valve retainer, the valve locks, the valve, or the spring must be changed; the spring pocket must be machined. Keep in mind that these modifications will change the valve spring installed height

Valve Spring Retainer to Rocker Arm Clearance

When installing the rocker arms, check to see that the inside of the rocker arms clear the spring retainers. Many rocker arms have a "relief" to accommodate large valve spring retainers.
Valve Spring Run-In

Each set of Lunati valve springs are hand-selected to keep load variations below +/- 10% of the next. However, it is important to "run in" your new valve springs at low RPM using the following procedure:

Start the engine and run the engine between 1500 and 2000 RPM until the engine reaches operating temperature.
Shut off the engine and allow the springs to cool.
After initial run-in, most springs will lose a slight amount of pressure. Re-check and shim up the valve springs if necessary. After the springs are "run in", spring pressure should remain constant until the point of replacement.