Valve Springs?
 

Here's a question for you...

According to the guy who sold me the heads that are now on my motor:

"These springs were recommended by lunati for soild flat-tappets up to .640 lift at 1.650 installed height. I was going to run Mopar's .557 soild cam at first, but changed my mind. I opted for the hydraulic .509 and installed the springs at 1.690 instead of 1.650 to reduce spring pressure on seat and open in order to work with the hydraulic."

What, exactly, does that mean? How do you install the springs higher than they're supposed to be installed? Shims?

Mike,

Yes there's a few ways to increase installed height, .. shims, ..
or a + valve lock. I'd still be concerned about the spring pressure
as there's a fair difference in spring rate between a Hy & solid spring.


Thanks,

Curtis

I kind of got the impression that installing the springs higher would lower the spring rate, is that the case?

Bump?

No, .. the spring "rate" refers to this, . .. if it takes 1" of travel to make a spring increase in pressure 100 lbs, .. .. that's a 100 lb. spring.

So, .. changing the installed height only changes the initial pressure the spring is set up at.

so, .. say you had a spring with a rate of 100 lbs per .100"
If it's installed at a height that compresses the spring .200"
you'll have 200 lbs on the seat.

Now if you open that spring to .500" lift, .. you would have an open
presure of ( 500 lbs + 200 lbs seat ) 700 lbs.

This is a very simplified way to look at it, since common valve springs
have multi springs all at different rates. The main reason that's done is
two fold. One to be able to change the spring set's rate as it opens, ..
and help control harmonics.

Soory it too so long to answer, .. 3 months behind at the shop.

Curtis

:? So thats not the way to go? Something would have to
give somewhere, right? :?

Well, .. yes & no.

If you have a spring designed with a rate for a roller cam, ..
and added height to the installed height so it only has say 100lbs of seat pressure, .. you'd have to check the open pressure to see if it's too
much for the hydr lifter, .. If not it's OK.

We have springs that are used for several different applications, ..
I have a spring, depending on it's installed height can be used for a roller
or solid. I have several springs that can be set up for solid or hydralic, ..
but it depends on the rate of the spring if it'll work. It's a ballence between open & seat pressure, .. open being most important.

All this tech discussion, the easy way, .. see if you have enough
installed height to get the proper seat pressure for the cam, ..
solid, hydr, roller, .. then check the open pressure and if that's OK too
you're all set.

Remember open pressure is always more important then seat pressure, .. On roller cams, . we set them up by open pressure and don't really
care what the seat pressure is, ..
but, it varies with the cam design, rpm range and type of engine, drag,
roundy round, .. road race, comp, bracket, pro stock, ..etc.

Did I make this clear, or more confusing ????

Curtis

heres another valve spring question for you...
i have a 69 340, with low compression pistons...running mid 12s last year on 87 octane. i have had the same valve springs for about 5 years, making at least a hundred runs a year. late in the season i broke a rocker shaft and 2 of my roller rocker arms. anyway..someone told me that the single damper mopar performance springs that i was running werent enough for my 528 purple shaft...although they came in a kit with that cam. should i go to a double damper spring for that cam? and honestly, how much of a difference is it going to make with fresh springs? i ran 12.68 earlier in the year, and times got progressively worse until it finally came apart late in the year.