Valve Spring Rates

GR124 · Postby **GR124** » Mon Nov 30, 2020 9:12 am

Currently setting up my head with the 74lb springs. Building a forged turbo engine. I was concerned about using springs with such a heavy rate. But after a bit of research with a turbo build it sounds like they are required. My engine will be a track only so at full song most of the time i think they will be fit for purpose.
Now to grind some valve tips to give me a bit more valve lash clearance.

The American · Postby **The American** » Mon Nov 30, 2020 10:16 am

GR124 wrote:Currently setting up my head with the 74lb springs. Building a forged turbo engine. I was concerned about using springs with such a heavy rate. But after a bit of research with a turbo build it sounds like they are required. My engine will be a track only so at full song most of the time i think they will be fit for purpose.
Now to grind some valve tips to give me a bit more valve lash clearance.

I am not sure what the deal is with the ratings on the Supertech springs. The 74lbs part number is what I used, and when I asked ST about them, they quoted 89lbs. The engine builder confirmed that they installed at 89lbs too. This is reusing the factory shims that the springs sit on in the head.

ralt · Postby **ralt** » Mon Nov 30, 2020 12:12 pm

Hi.
89lbs Would be about right I use the same in my NA but they are NB springs 1/16 inch shorter no problems with hydraulic lifters.

plohl · Postby **plohl** » Mon Nov 30, 2020 9:36 pm

It depends what seat you're using for them.

{edit: I just repeated myself from the first page}

GR124 · Postby **GR124** » Tue Dec 01, 2020 9:41 am

plohl wrote:It depends what seat you're using for them.

{edit: I just repeated myself from the first page}

ploh, do you refer to the spring "seats" or shims? not the valve seat?

I assuming you are referring to the valve on valve seat pressure will change depending on what spring seat/shim thickness is used?

plohl · Postby **plohl** » Tue Dec 01, 2020 4:06 pm

Sorry, that was a confusing.
I am talking about steel inserts which the valve spring sits on - spring seat. It's safe to assume the length from back of the valve (where it contacts the valve seat on the head) to the collet is constant, so changing the spring seat (closer or further away from the collet) will change the preload on the spring - which will change the seated force (/pressure).

that's probably even more confusing now.