Valve Spring Compatibility
 

Lunati recommended their 73121 springs for my new cam. I already have some PAC 1924. All except the rate looks pretty close to me, but admittedly I'm guessing. Any thoughts on whether the PAC springs below would be alright to substitute for the Lunati springs below? Cam specs at the bottom and this is all going in a 494ci (4.30"x4.25"). Thanks.

Lunati 73121 Dual with Damper

Install Load: 142
Install Height: 1.940"
Open Load: 402
Open Height: 1.250”
Coil Bind: 1.089"
Rate (lbs/in): 377
Lift Max (in): .690
O.D. Outer: 1.540"
I.D. Outer: 1.140"
I.D. Inner: .794"

PAC 1924 Dual with Damper

Install Load (LB): 144
Install Height: 1.900”
Open Load (LB): 403
Open Height (in): 1.300
Coil Bind Max (in): 1.125
Rate: 431
Lift Max (in): 0.650
OD (in): 1.540
ID (in): 1.140
Inside Spring ID (in): 0.754

Voodoo 20110713 Cam


Advertised Duration (Int/Exh): 292/300
Duration @ .050 (Int/Exh): 241/249
Gross Valve Lift (Int/Exh): .625/.625
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2600-6600

Re: Valve Spring Compatibility
 

They look compatible to me.

Re: Valve Spring Compatibility
 

Dave -- they look pretty much the same ... just make sure to check for coil bind. TAZ

Re: Valve Spring Compatibility
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: L78steve</div><div class="ubbcode-body">They look compatible to me.</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: earntaz</div><div class="ubbcode-body">Dave -- they look pretty much the same ... just make sure to check for coil bind. TAZ</div></div>
Thanks guys. I was mainly concerned with the Rate. 377 vs 431. I'll double check the .036&quot; difference in coil bind too. A reputable machine shop is setting the heads up this week, so hopefully they should be good to go. I just didn't want to give him something that isn't compatible.

Re: Valve Spring Compatibility
 

One more question... Can someone confirm the valve spring &quot;max lift&quot; refers to the max cam &quot;gross valve lift&quot; it can handle?

Re: Valve Spring Compatibility
 

The higher rate spring will be a benefit at higher RPM's. If your not running at High RPM's use the lower rate spring.

Re: Valve Spring Compatibility
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: L78steve</div><div class="ubbcode-body">The higher rate spring will be a benefit at higher RPM's. If your not running at High RPM's use the lower rate spring. </div></div>
Thanks Steve. I doubt I'll be seeing very high RPMS, but I already have the higher rate springs. I'm sure less than 6k rpms. My 69 isn't set up for that kind of power and wouldn't handle all the torque and hp right now. If it isn't detrimental to my cam I'll just go with them so my buddy that is buying the parts doesn't have to spend another $120 or so on springs. He's already up over a grand on the cam and lifter set alone to make my motor what it was supposed to be when I bought it. Long story from another thread, but he got screwed by a builder and didn't know it until I bought the motor from him.
What do you think about the lift question?

Re: Valve Spring Compatibility
 

Gross is before loss. Total is what you end up with. If you have a clearance of .030 subtract that from gross. So at .625-.030=.595
Even with Hydraulic there will be some lift loss.

Re: Valve Spring Compatibility
 

I think you'll be fine. Or possibly take out the damper and get the rate down some too. I wouldn't second guess this with solid just not sure as I've never ran hyd cam stuff.

Dave BTW that cam only &quot;works&quot; to 6200 anyway. 2600-6200

Re: Valve Spring Compatibility
 

Dave, the 1924 are the springs I gave in my motor, they are installed at 1.92