math class needed on valve springs

gsa612 · 12-08-2018, 01:43 PM

What is the valve lift on the int. and exh.?. gsa612

FireSale · 12-08-2018, 04:59 PM

If you can find a comparable spring on the PAC Racing site, this link to their spring rate calculator might help.

https://www.racingsprings.com/index..../?sku=PAC-1224

Edit: Change the part number to your match.

ss3011 · 12-08-2018, 06:08 PM

The basic formula is F=kX . F is the force , k is the rate , X is the difference in spring height from the length of the spring when it is not loaded .

Kevin Panzino · 12-09-2018, 11:47 AM

Quote:

Originally Posted by ss3011

The basic formula is F=kX . F is the force , k is the rate , X is the difference in spring height from the length of the spring when it is not loaded .

This is correct.

To add to above, the spring rate is stated as the force generated per unit of compression. Ex: 1,000 Lbf/Inch, 1,700 N/cm etc.

Also, its spring FORCE, not pressure. Spring pressure is a common misnomer racers seem to always use, and it just wont die. Its entirely wrong. Its not a pressure, Its a force.

gmonde · 12-09-2018, 10:11 PM

Quote:

Originally Posted by gsa612

What is the valve lift on the int. and exh.?. gsa612

.457

gsa612 · 12-10-2018, 10:09 PM

The Pac 1220X spring shows 160 lbs seat press.at 1.900 and 400 lbs open at 1.250 which is close to coil bind.If you subtract your lift of .450 from the 1.900 your at 1.450 open.That may give you only 360lbs press.You need to find a "short" spring with your low lift that will give you the open pressure your looking for.Even if you do find a long spring that gives you the numbers, but is .300+ from coil bind your going to have valve stability issues. Have you looked into Comp cams ?. gsa612

FireSale · 12-10-2018, 11:05 PM

What's the application here? It doesn't really make sense to talk pressures when we don't know what is being asked of the engine. I run PAC 1427 springs - conical for a BBC - in a SBF with NASCAR type iron heads. Stuff gets mixed up when all you want is GO...

Note: A PAC 1409x at 1.8 will give you pressures of 175/384. I'd give up on a 1.78 IS, it's too hard to shim to. 1.8 or 1.85 are common.

Note 2: What is the seat size?

Ask questions and give info. I didn't so I have 4 sets of springs now............

12-08-2018, 01:43 PM	#1
gsa612 Senior Member Join Date: Jan 2008 Location: 100th Meridian Posts: 569 Likes: 116 Liked 280 Times in 139 Posts	Re: math class needed on valve springs What is the valve lift on the int. and exh.?. gsa612

12-08-2018, 04:59 PM	#2
FireSale VIP Member Join Date: Feb 2014 Location: Lakewood Washington Posts: 1,407 Likes: 29 Liked 237 Times in 126 Posts	Re: math class needed on valve springs If you can find a comparable spring on the PAC Racing site, this link to their spring rate calculator might help. https://www.racingsprings.com/index..../?sku=PAC-1224 Edit: Change the part number to your match. __________________ Dale Shearon 68 Mustang 6394

12-08-2018, 06:08 PM	#3
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: math class needed on valve springs The basic formula is F=kX . F is the force , k is the rate , X is the difference in spring height from the length of the spring when it is not loaded . Last edited by ss3011; 12-08-2018 at 06:09 PM. Reason: Clarify

12-10-2018, 10:09 PM	#6
gsa612 Senior Member Join Date: Jan 2008 Location: 100th Meridian Posts: 569 Likes: 116 Liked 280 Times in 139 Posts	Re: math class needed on valve springs The Pac 1220X spring shows 160 lbs seat press.at 1.900 and 400 lbs open at 1.250 which is close to coil bind.If you subtract your lift of .450 from the 1.900 your at 1.450 open.That may give you only 360lbs press.You need to find a "short" spring with your low lift that will give you the open pressure your looking for.Even if you do find a long spring that gives you the numbers, but is .300+ from coil bind your going to have valve stability issues. Have you looked into Comp cams ?. gsa612

12-10-2018, 11:05 PM	#7
FireSale VIP Member Join Date: Feb 2014 Location: Lakewood Washington Posts: 1,407 Likes: 29 Liked 237 Times in 126 Posts	Re: math class needed on valve springs What's the application here? It doesn't really make sense to talk pressures when we don't know what is being asked of the engine. I run PAC 1427 springs - conical for a BBC - in a SBF with NASCAR type iron heads. Stuff gets mixed up when all you want is GO... Note: A PAC 1409x at 1.8 will give you pressures of 175/384. I'd give up on a 1.78 IS, it's too hard to shim to. 1.8 or 1.85 are common. Note 2: What is the seat size? Ask questions and give info. I didn't so I have 4 sets of springs now............ __________________ Dale Shearon 68 Mustang 6394 Last edited by FireSale; 12-10-2018 at 11:24 PM.