I don't know if this has ever been covered before...

I have twins that make about 60 PSI (with woosy injectors). If the valve spring is able to apply 75 pounds of satic pressure to keep the valve closed, is that enough to keep it closed when there is no cylinder pressure??

I know that on the compression stroke the combustion pressure will be able to hold the valves up, but what about on the exhaust stroke when the 60 psi is pushing againts the intake valves???

If you look at it one way, lets say that the boost does push the valve open, would it assist in evacuating the exhaust gasses???

Just a brain fart....

And if the above is a problem, where can i purchase heavy rated valve springs?


Justin-

 

I've heard that Cummins has heavier/ better springs available. I'm pretty sure there's one of our NE members here that is running titanium valvetrain pieces. He may know the part numbers or something fun like that.

I didn't see any ill effects when replacing a headgasket after 4300 miles of 65pi daily use.

brandon.

 

Spoke with Ken Jones regarding the heavier spring question...

He said the stock "60 #" springs were enough to handle 105 PSI of boost on a 24 valve.

Thats ok in my book. I don't plan on seeing over that #.

 

Guys:

The valvesprings are rated at 60#, but what does that number mean? Does it mean 60lb of spring pressure? Is this when the cam's on its base circle or when the valves are fully open? Or does this mean they will hold 60LB PER SQ INCH of manifold pressure?

60lb and 60psi are HUGELY different.

Also, remember that the pressures at different points in the intake tract or going to very wildly based on velocity and volume. Just because you have 60psi on the boost gauge doesn't mean you have that much pushing on the intake valves- it's probably much less. Once that 60psi intake air column (assume you meaured in the hat) is divided up and put in to the smaller intake ports, where it is accelerated, the pressure is going to be much less.

Bernoulli-- more velocity=less pressure and vice versa.

the non-twinned Justin

jlh

 

Justin,

There are several issues with the stock 24V springs and I've got valve marks in my pistons to prove it. The intakes float easily at higher rpm combined with boost. You don't show a Blue Chip Redline box in your sig. but watch out if you are running a stock cam, springs and ~60 some boost any serious rpm. With a decent cam, some valve work and shimmed stock springs I was able to get just over 4000 rpms at 60psi before valve contact (P7100 conversion). I know of a truck that has aftermarket ($'s) valve springs and billet crossovers yet the valves are floating at 3800 rpm single turbo (with a Redline box and hotrod VP44). When the stock springs are new they do pretty well but after a few miles if you put them in a spring tester some will test very weak while the others maintain their proper strength. Maybe someone will chime in with a source for quality springs?? The Cummins springs are inexpensive and I'm guessing that the wire they are made of is too............................. Larry

 

Can't somebody like Crane or Isky put something together for you?

 

I ran ISki dual springs on my Sigerson racing cam in college, the cam was wore out 20,000 miles later. Make sure the cam can handle the extra pressures. no roller rocker yet.