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Discussion Starter · #1 ·
long story short. My car dropped a valve the crower retainer fell apart. and pushed in to my crower springs. Now when I tried to start the car after it happened it wouldn't crank. When I turn it by hand I can feel the piston hit the valve and then it won't move. The cams and head were installed by a professional engine builder and I know it's a faulty part, just by looking at it. No my concern is when that vale hit the piston. they are SRP pistons and I am under the belief they are fordged(are they). what damage could have been done to my piston?
 

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Yes the SRP pistons are forged. Good luck with the damage.
 

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Discussion Starter · #3 ·
Will there be damage to this piston? or just the valve. When my motor was built the pistons were notched so maybe it's just in the cut out?
 

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yeah...i dont think i'm going to use the ones i have now...cause they are crower....i'll just use the valvesprings
 

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Important things to know:

Valve Spring Pressures
Cam lift/duration
Piston to Valve clearance

All of these could have led to a failure of the Ti retainer...I had an hour long conversation with the guy that used to produce all of the Portflow Ti retainers, Portflow went to another manufacturer ~1 year ago...any of the people that have had issues with the Portflow retainers are from the newer manufacturers retainers.

Austin
 

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austin: were these galled Portflow ti retainers the old or new retainers?




my very informative

Valve springs (and their shortcomings) are generally misunderstood by the import community. A valve springs are much like any other spring, in that they’re made from steel and they do their job of compressing under load and returning to their original (non-compressed) height when the load is diminished.
If you bend a piece of steel back and forth, it’ll eventually break because bending it causes the metal to fatigue…and it also generates heat. Other than the fact that valve springs are made from pure alloys and heat treated to make them “remember” their shape, you can never lose sight of the fact that they can only be “bent” back and forth (compressed and released) so many times before they fail.
Keeping this in mind, it should be evident that the more you “bend” or compress the spring, the sooner it will fail. The frequency at which the spring is compressed also plays a part, because the higher the rpm, the more spring cycles occur per second/minute/ hour/mile…you get the idea.
If you bend the spring less, it’s going to last longer, and if you bend it less frequently, it’ll also last longer.

Applied to automobile engines….the larger the cam/valve lift, the more the spring is compressed, so big cams will shorten spring life, just as high rpm will. When the springs begin to get “tired”, they lose their ability to control the masses of the valve, retainer, rocker arms, etc…so you float the valves and if you’re running marginal piston to valve clearances, well…..two objects can’t occupy the same space at once…and kaboom.

If you have a spring that “sets-up” with a height of 1.350” and coil binds (stacks solid) at .825”, you have .525” of possible compressible height to use. Unfortunately, you can’t let the spring actually stack solid in the real world because that will really shorten its life. If we give it .025” of “breathing space”, now we have .500” of compressible height to use.
Now, if we use a spring that sets-up taller (say 1.410”), yielding the same approximate valve seat pressure, while still compressing to the same .825” dimension, we’d have .585” of possible compressible height. Using .025” for “breathing space”, we end up with a spring that can handle .560” of usable compressible height.

If we take the two spring examples and run a camshaft that will net .500” lift at the valve, the first spring is being compressed to it’s limit (.500”), while the taller spring still has .060” of compressibility left in reserve…and therefore it’s not being as greatly stressed.
You may say that .060” isn’t much, but in these engines where we deal with almost “micro-tolerances” that’s a lot.
If each spring combination is run with the same camshafts and at the same rpm levels, it shouldn’t take a genius to determine which spring will last the longest……

Making more distance for a spring with increased height requires that the retainer be raised, or the spring seat pad on the head be lowered…or both.
Machining the spring pad on the head lower isn’t an option on heads we port for all-out engines because we already raise the roofs of the ports to the point where the amount of material under the spring pad is minimal. That being the case, we chose to machine the steel spring seats that rest on the pads, so they’re thinner and we use a retainer that still sits on the valve in the same location as stock, but the registers for the inner and outer springs are raised .060”.
This in no way effects the placement of the valve stem tip the rocker arm contacts, so we’re not screwing with cam/rocker/valve geometry when we do this.

Since the outer portion of the +.060” retainer sits .060” taller than a stock retainer on the valve, it’s edges can contact the underside of the rocker arms, if they aren’t relieved or radiused to make proper clearance. As you’ve seen in the 2-liter article, we remove only enough material from the underside of the rockers to provide minimal clearance, rather than taking a chance and removing so much that the rocker’s weakened. All the rocker arms are slightly different, so we relieve them and fit them individually. This process takes about 2.5 hours to accomplish for the full set.

If this seems to be “excessive”, you have to remember that I’ve been dealing with cylinder heads and related components for most of my life. The valvetrain is the MOST fragile part of the engine. More engines succumb to valvetrain failure than any other ailment. If you want the valvetrain to last until the end of the race, you have to build it so the components are stressed as lightly as possible. We have the ability to increase spring life by using springs that aren’t operating at the limits, like stock height springs are with cams or .500” lift and more.

As for camshafts…once again, I prefer to use cams that don’t stress the rest of the valvetrain components. If you can configure ports that are capable of feeding an engine adequately using a “small” cam, while still achieving winning performance, you should go in that direction. If you do, you’ll run just a quickly and fast as the other guy running the “killer” cams, but you won’t have the reliability penalty he’s paying. It just makes good sense…it always has, and it always will.

Discussing cams, there are several things you have to examine when looking at different grinds. Lift and duration are the typical specs that most pay attention to, but you have to look closer at the durations rated from 0.0”, .020”, .040”, and .080”.
It’s one thing to have a lot of duration from “zero”, but cams that have big duration rates from the other measuring points will tell you a lot more about the character of the cam. Cams with long duration from the higher lift measuring points have not only more duration under the lift curve, but they’re also accelerating the valve open and closing it quicker. As the opening and closing rates are more aggressive, the toll they take on the valve springs increases, because the spring compression rates are higher, so look at all the specs on cams that you can get your hands on before buying.

In response to the JUN4 cam question….I just received some NEW JUN3’s that I’ve had on order for 5 months from Japan. These cams have the “old” low lobes, but the intake lobes measure a full .500” at the valve. on the JUN4’s, it’s pretty obvious that they’ve attempted to make cams that make tuning the VTEC “dip” easier. I think that this should certainly help, especially in the road racing community.

As for JUN valve springs….I don’t personally feel they’re adequate for JUN3’s. on Todas, you’ll also find that power begins to fall off over a relatively short time, as their valve springs begin losing their “stuff” rapidly.

We typically buff the ends of the springs to make them less abrasive on the titanium retainers, so wear isn’t a huge issue. Titanium, even coated titanium isn’t the longest wearing material known to man anyway and my thoughts are that if you’re going to go “light”, you’d better be prepared to pay the price in periodic maintenance. The lighter you make things, the more power you make, the higher the rpm you scream the engine, the shorter the life of each and every component in the mix will be…and that’s something that you simply can’t afford to lose sight of.

You can't set up a spring that's intended to set-up at 1.350" at 1.380" and still have the pressure you need on the valve seat. As an example, a spring combination that nets 65psi of seat pressure @ 1.350" would only provide 53 psi at 1.380" and that's not adequate to keep the valve returning to it's seat properly. You can't get there by using a stock-height spring.....

Forgot to mention that when theres any valvetrain separation, the springs are frequently bouncing all over the place, not touching either the spring seat, or the retainer simultaneously. This bouncing will eat the crap out of the underside of titanium retainers, so part of the wear issue is likly do to the use of inadequate springs....
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I strongly recommend that if you do choose to get ti retainers that you nitride coat the springs. There's several SAE papers out now suggesting that this is the way to go to reduce wear and galling issues assuming the installed height, rocker to retainer clearance, and valve seat pressures are within tolerances.
 
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