I have found a perfect, inexpensive valve spring from Scoggin Dickey (Heavy Duty Z28 spring) Its 130#seat, 350# open and handles .550 lift from a hyd. roller. 2 potential problems are that the O.D. is 1.25". Will this work on the Edelbrock RPM head? The RPM has 1.45 OD springs...will the 1.25 slide around? And also are there any cam valve train geniouses out there? My cam guy said that an open pressure of higher than 340# will squeeze the oil out of the hyd. roller lifter. Any truth to this?

 

No the oil won't "squeeze out" of hyd roller lifters. Yes I've built enough motors to know.

Don't downgrade your properly equipped heads to stock springs.

http://www.compcams.com/Technical/Cu...ML/128-169.asp

Scroll down to pg 138 and look at the springs that are recommended for hydraulic rollers. Note that the 1.25" springs (which incidentally are a better product than the stock ones from SDPC) are only recommended for hyd rollers up to .500" of lift; and 1.45" ones are recommended as teh "premium upgrade" for even the SMALLEST hyd roller.

I'd suggest running Comp 987s, and not worrying about it any further. They're what I usually run in hyd roller motors; unless I have 1.55" pockets in the heads. In which case, I run a spring that fits that. And I have no trouble with that combo either.

 

[QUOTE]Originally posted by sofakingdom
[B]No the oil won't "squeeze out" of hyd roller lifters. Yes I've built enough motors to know.
[QUOTE]

Yes they will, put one in a vise.





HeHe, but not when the engine is running

 

The 1.25 OD Heavy Duty SDPC is their upgraded version of the stock Z28 spring. Its smaller in diameter but it has stronger specs than the RPM spring. How is that downgrading? GM has crate engines with hydraulic rollers and springs that have a smaller diamter than 1.33". Why is the larger diameter more important if the seat and open pound specs are weaker? Just curious

The reason that I am going with a 1.25OD is because right now I have the L98 heads that i'm keeping for just one more year. I've changed cams to a lumpier cam but I need a spring upgrade. the L98 won't take a 1.45OD or more spring. And it would've been nice to swap these springs over to the RPMS when I get them. The RPMs have 120# seat/ 320# open pressure which is lower than the recommendation for the cam.

 

I am runnig the SD1007 springs from Scoggin Dickies . They are 1.25 "diameter. 1.8 "120 lbs and 1.2 350 . They say they have run many enignes with 570 lift and had no problems .

 

Take a coat hanger wire, and bend it back and forth a few times, until it breaks; and then feel the ends, as fast as you can.

OK, now that you've taken care of the burn and the pain has subsided, understand that THAT'S what your valve springs are doing, the whole time the engine is running. They're little pieces of wire, all coiled up, and bending back and forth every time the valve moves. The more you bend them, the hotter they get; the hotter they get, the weaker they get, and the more likely they are to break; and the less effective they are at controlling teh valve.

On top of that, imagine taking a spring, and hitting it with a hammer. What will happen, is NOT that the spring will compress evenly, and bounce evenly back. Instead, what WILL happen, is that a "wave" of compression will start at the end you hit, and travel along the length of the spring; reach the other end; "bounce" back; and so on, damping itself out by way of the energy absorbed in heating the metal. While that wave is traveling, wherever it happens to be, the coils are closer together than anywhere else; and if adjacent coils hit each other, they sset up their own waves, which result in potentially HUGE forces - bigger than the original hammer blow in fact - being transmitted to the ends of the spring. The forces in fact are often comaparable to those produced by coil bind; because they are, in effect, THE SAME THING.

So; operating a valve spring anywhere near its limits, is an invitation for disaster. It's almost impossible to have "too much spring", from the spring's point of view.

Going back to the heating thing, a spring with 1.45" OD has about 12" more length of wire than an otherwise identical spring with an OD of 1.25". Which means, that the heating effect per unit length is 12% less. Which means, that you can add 12% more lift safely, without making any other changes, by increasing the OD; or conversely, you can reduce the temperature rise in the spring, and thereby increase its life, by making the OD increase.

Springs are CHEAP. Especially those stock ones. (Incidentally, the reason they're called "Z28" springs, is because they were stock on the old solid-cam Z28s. They're still "stock".... maybe not "stock" the same as the ones you have now, but they're still "stock" for something.) If you just gotta do that to your current heads, then go on and do it; but when you get better heads, throw those away or sell them with the 083s or whatever. You'll only be out a few coins anyway. Then just put the right springs on the new heads. For all of the reasons above, plus others I didn't feel like taking the time to talk about.

Also, look at the GM cam profiles, and you'll see, they're REAL LAZY compared to aggressive aftermarket ones. In fact, alot of GM's roller cams, are merely copies of the corresponding flat tappet profile; for instance, the "peanut" roller cam is identical to the LG4 cam. GM can get away with ALOT less spring on their cams because of that. It's therefore meaningless to compare GM crate motor setups to max effort aftermarket cams.

There's ALOT more to valve springs and why they're chosen as they are, than just some claimed "max lift" spec. People who pay attention to nothing but that one spec, are the ones you usually see with wiped lobes and broken parts; those of us who look a little deeper, are the ones that get good long-term results out of these aggressive modern cams.

 

yes but their off ls1 heads.

 

Ummmm, no...

Actually they were off of LT1 heads. 70-71 LT1, that is.

 

I'm not looking at only one spec, I'm looking at seat pressure, open pressure, coil bind, lift capability, OD and ID. Basically the whole deal. I can only use a small diameter spring on my L98 heads because thats all that they will take without machining. I'm not machining a head that I'm soon to get rid of. About the RPMS, yea, I can go with aftermarket 1.45OD for my cam's spring requirements. If I need them. Thats another question that I'd like to ask...and I may just start a whole new thread for that since most people won't find my question in this thread now. The question is: Will a 1.45OD dual spring with 120#seat and 325# open pressure and a .575 lift capability handle a .529 hyd. roller lift cam that requires about a 130#seat and 325# open pressure?
Basically its 10#s shy of the cam's recommendation for the seat. These are the RPM springs that come on the head and this is my Lazer cam spring recommendation. I just thought that I'd ask because it would be really nice to have a head that had springs that came compatible with my cam...right out of the box

 

oh so you mean LT-1

 

No. I mean LT1. It was the RPO code for the motor. RPO codes don't have hyphens. Don't now, didn't then. Even though the Z28s it came in, had badges that said "Z/28".

I have no clue where the hyphen business came from. I certainly don't recall people using it when the motor was introduced. In fact, I can't recall the hypen being added until after the "Type LT" (the forerunner to the Berlineta) being introduced. I guess I first saw it in about 75 or so.

 

the 92'-97' are referred to as LT1's. the early corvette and camaro engines are called LT-1's. you can see the hyphen on the hoods of corvettes stating the engine as "LT-1"

 

It's the RPO code for the motor. RPO codes don't have hyphens. Don't now, didn't then, never have to my knowledge.

They don't have slashes either. Which is why we don't call 69 Z28s "Z/28"... regardless of the trim.

Adding the hyphen pretty much identifies one as someone who wasn't around at the time.

Here's a '69 "Z/28" emblem. It's still a Z28, not a Z/28.

 

Is that you, RB? Gotta be. There's only one technically competent person on this board that I know of that can put the proper perspective on things...

 

like that?