Upgrading valve springs

[pc]

Wouldn't the stronger spring make it seat more firmly while under high boost?
I would assume that the firmness of the seating should also be taken into account and not just whether or not there is enough boost to blow the valve open.

[tsoob]

I had to get upgraded valve springs.
I did heaps of dyno runs on 25psi and it was fine, did about a weeks driving on 20psi. Then one day it got valve float and bent the valve.

So I upgraded springs and have never had an issue.
Also when I did upgrade them the car felt much much stronger at high boost levels!!

Gary did my head and made the same recomendation, and as barry said its ok for a while then you get a problem, I have had so many issues in the last year or so you would be insane to "risk it" it WILL cost you more later on.

[Mr Revhead]

interesting the some have issues straight away, and others never

maybe its in the prep of the head?
as MAGN1T said earlier, if your springs take 35 psi to move them, and your running 20psi, there shouldnt be an issue.

[Bazda]

Some people have issues, some dont, I guess its how old your springs are and how worn they are.

measure them first, if they are near the factory specs should be ok.

Going from the blacktop manual it says they should be:
Maximum squareness: 2.0mm max
Free length: 48.97mm
Spring tension: 149-165N (33.5-37.0lbf) @ 37.7mm

[~SlideWays~]

Pm them? The head specialist sad anything over about 15psi needs uprated springs. He is a head specialist he does this for a living is he wrong? But then how is gasman and flygt4 getting away with it?

Well I run just under 18psi with standard smallport head no probs. Have taken it to a couple of track days now and holds boost no probs.

How much power do you need for you the "have fun"? Kinda sounds like you are just wanting 20psi because its a nice round number?

[Bazda]

the 16v springs are better cos they are bigger and stronger.

20v springs are small and weak!

[TRD_ZERO]

Pm them? The head specialist sad anything over about 15psi needs uprated springs. He is a head specialist he does this for a living is he wrong? But then how is gasman and flygt4 getting away with it?

Well I run just under 18psi with standard smallport head no probs. Have taken it to a couple of track days now and holds boost no probs.

How much power do you need for you the "have fun"? Kinda sounds like you are just wanting 20psi because its a nice round number?

Im wanting to run 20 psi as my engine is capable of (well atleast i thought it is was) and thats only every now and again. As other guys one here running the same setup not having any issues

[IH8TEC]

25psi on std 16v springs 8,000rpm and lots of abuse haha,

[RomanV]

Valve spring tension has got nothing to do with boost. Revs , yes. Think about it. How can they blow open?

Because boost is a measure of pressure in the intake manifold, not pressure in the combustion chamber.

The valves'll let air into the 'other' cylinders from the manifold, if boost is forcing them open.

[~SlideWays~]

25psi on std 16v springs 8,000rpm and lots of abuse haha,

Hey how much torque is your motor making?

[TRD_ZERO]

I saw the head reconditioner and he is adament that i shouldnt run anything over 12-13psi and 15psi is a really bad idea. No testing of my valve springs have been done yet. Ive been reccomended to the guy by people on here since he supposibly know his stuff about 4ages, maybe only the dirty 16vs though.

[Bazda]

who is this guy btw...

[TRD_ZERO]

IM not bad mouthing this guy i dont really know him ive only heard good things about him hence the reason i went there and he is fantastic to deal with. Just questioning his valve spring theory. Cyliner head shop sunnybrae rd Glenfield. I think thats what it is called.

[Bazda]

Oh yes we know the guy very well.

He does know heads, but he prob doesnt know much about 4agtes and how much power you can actually put through them.

[TRD_ZERO]

Yeah ive been told by alot of pople in the industry to go there for head work. Super friendly too. Just dont want to get vlave springs if i dont have to.

[MAGN1T]

Because boost is a measure of pressure in the intake manifold, not pressure in the combustion chamber.

The valves'll let air into the 'other' cylinders from the manifold, if boost is forcing them open.

Not when the pressure in the combustion chamber is higher than boost pressure.

35 pounds on the seat.
1 inch or so diameter.
.78 or so square inches.
About 50 PSI to force open.

That means manifold pressure would need to be about 50 PSI greater than the combustion chamber.

It will never happen.

Steve

[rollaholic]

i think the concern is more about the valves on cylinders that arent on a compression stroke being forced open, say for example on exhaust when theres little pressure in the cylinder.

[Bazda]

http://www.cranecams.com/?show=newsLetters&no=65

[MAGN1T]

Obviously written by the sales and marketing department.

Don't stop there though, you also NEED new cams and they'll never work properly without titanium retainers, they're absolutely essential.
Triple large fries FTW.

72 pounds of seat pressure? it depends on the pressure inside the cylinder at the time.


For as long as people have been modifying cars, there's always been others trying to sell parts that aren't needed.

Steve

[fivebob]

Actually I think the reason behind it has nothing to do with the valves being forced open. Rather, it is that the required seat pressure to move the valve has been reduced, therefore the valve will accelerate faster and you will then get more valve loft.

The higher you rev the engine the greater the valve loft. Which at some point in time will result in valves meeting pistons and the inevitable bent valve.