Valve springs

[olgreydog7]

You have 65 lbs of seat pressure. Run 15 lbs of boost and that seat pressure is now down to 50 lbs :uh oh:

No. Spring pressure is force. Boost pressure is actually pressure which is force per unit area. Multiply 15 psi times the valve surface area and that is the force you get.

 

[na svt]

I went with PAC springs. On order now. What had happened is my gas pedal go caught on my carpet causing the car to over rev floating two valves and bending two valve stems. So I'm replacing the valves seats and springs. Just to beef it up a bit. Not doing cams or anything. The bottom end is built and it takes about 20 psi. So it's time to beef em up

You could have saved a ltota money by going with the $200 BTR's (manleys) as they use the stock retainers.

Changing the valve seats is expensive and isn't necessary. Seals yes, seats no.

 

[na svt]

No. Spring pressure is force. Boost pressure is actually pressure which is force per unit area. Multiply 15 psi times the valve surface area and that is the force you get.

:rockon:

 

[yzracer931]

Chaning the valve seats is expensive and isn't necessary. Seals yes, seats no.

He floated and bent two valves and you are saying changing the seats isn't necessary?

 

[SlowSVT]

No. Spring pressure is force. Boost pressure is actually pressure which is force per unit area. Multiply 15 psi times the valve surface area and that is the force you get.

.............which is about 1 sq in per valve.

A bit "oversimplistic" I agree but it gets the point across.

 

[na svt]

He floated and bent two valves and you are saying changing the seats isn't necessary?

The only seats that have to be replaced are those that are damaged. Also, if all the seats have to be replaced the cost fwill be far more than the worth of the heads.

 

[blacksheep-1]

.............which is about 1 sq in per valve.

A bit "oversimplistic" I agree but it gets the point across.

that's what I was trying to point out..

I guess that's possible, but I'd have to see it with my own eyes. that or the valve springs are made from ball point pen springs.
Using a SBC I think this equation is about right..
2.2 intake valve @ 16 psi boost
1.1 x 1.1 x 3.1416 x16 = 60.82 pounds of pressure on the intake side of your valve.

 

[yzracer931]

The only seats that have to be replaced are those that are damaged. Also, if all the seats have to be replaced the cost fwill be far more than the worth of the heads.

At minimum those two need to be replaced and the rest of the valves checked for run out. Then lap them all back in to make sure you have adequate seating surface.

 

[olgreydog7]

that's what I was trying to point out..

Sorry, didn't realize what equation you were using :beer:

 

[99cobra09]

Should have gone with Brian Tooley Racing springs, save a lot of cash for good quality, best bang for your buck. I'm using those, with high c.r boosted application.

 

[blacksheep-1]

Sorry, didn't realize what equation you were using :beer:

no worries

 

[N/Angel]

I know the last post has been a while, but has anyone used the PAC dual springs?
looking for the extra piece of mind at higher rpms

 

[na svt]

The dual springs work well but aren't needed in engines operating under 8000.

 

[Shaunk]

To add to this how many people are actually setting installed heights?

 

[gt347mustang]

To add to this how many people are actually setting installed heights?

Interested to see this.

Is the installed height the same on both intake and exhaust?

I'm having valve float issues with 45psi of backpressure on stock springs(or at least i think im having float issues).

 

[na svt]

45psi of back pressure is the problem, not the valvesprings.

How much boost?

The exh and intended spring heights are the same.

 

[SlowSVT]

I'm having valve float issues with 45psi of backpressure on stock springs(or at least i think im having float issues).

 

[gt347mustang]

Lol! I knew you guys would freak out.

Boost is at about 22 when that happens. Its far from ideal, but I'm not overly concerned. I just need a few more pounds of seat pressure to hold the damn valve still. I think it also has something to do with running FGT cams and stock springs. I'm going back to 98 cobra cams when I swap out springs.