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#1
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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"
![]() 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
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-Dave Semper Fi! 69 Camaro SS396 L34 X66 |
#2
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They look compatible to me.
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"Knowledge is good" Emil Fabor 67 L/78 Camaro SS/RS H-H,1W,2LGSR,3SL,4K,5BY. (Sold) 70 L/78 Nova M-21,Black Cherry,Sandalwood Int. 09 Pontiac G8 GT Premium,Sport,Roof. Liquid Red. |
#3
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Dave -- they look pretty much the same ... just make sure to check for coil bind. TAZ
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You've never lived until you've almost died -- for those who fight for it, life has a flavor the protected will never know! |
#4
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<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" 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.
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-Dave Semper Fi! 69 Camaro SS396 L34 X66 |
#5
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One more question... Can someone confirm the valve spring "max lift" refers to the max cam "gross valve lift" it can handle?
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-Dave Semper Fi! 69 Camaro SS396 L34 X66 |
#6
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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.
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"Knowledge is good" Emil Fabor 67 L/78 Camaro SS/RS H-H,1W,2LGSR,3SL,4K,5BY. (Sold) 70 L/78 Nova M-21,Black Cherry,Sandalwood Int. 09 Pontiac G8 GT Premium,Sport,Roof. Liquid Red. |
#7
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<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?
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-Dave Semper Fi! 69 Camaro SS396 L34 X66 |
#8
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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.
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"Knowledge is good" Emil Fabor 67 L/78 Camaro SS/RS H-H,1W,2LGSR,3SL,4K,5BY. (Sold) 70 L/78 Nova M-21,Black Cherry,Sandalwood Int. 09 Pontiac G8 GT Premium,Sport,Roof. Liquid Red. |
#9
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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 "works" to 6200 anyway. 2600-6200
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'58 Apache pick up restomodding with twin turbo 522 '78 Z28 4sp being restored '78 Z28 32,000 survivor, Og Yellow paint, AC. '70 W30 convert TRIBUTE '70 CANADIAN Nova SS396 L78 Pro Street '69 CANADIAN Nova SS 396/350 hp '67 CANADIAN Nova SS 427 10 sec. driver '66 CANADIAN Nova SS Race Car '69 FIREBIRD Tubbed Racecar '61 CANADIAN Pontiac Bubble top 409+/4sp (SOLD) '31 ALL STEEL Chevy P.U. GONE (EX-WIFES NOW) |
#10
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Dave, the 1924 are the springs I gave in my motor, they are installed at 1.92
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1969 ZL1 COPO Camaro 11.60@120 F.A.S.T 21 1971 LS6 vette 12.20 @118 PSMCDR |
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