Author Topic: New Valve Springs for '69 302...?  (Read 3310 times)

69Z28-RS

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New Valve Springs for '69 302...?
« on: March 24, 2009, 04:50:10 PM »
I have  a pair of original '69 Z28 heads ('186') at the cylinder head shop for rework... cleaning, magnafluxing, pressure testing, new guides, new valves, springs, etc.  Everything is ready for assembly now, but the shop today told me that they seldom used the 'double springs' (with the damper inside) anymore; instead they typically use a single 'conical spring'... supposedly smaller diameter at the top than at the bottom?

I'm open to improvements, but I hate to change a good thing without understanding 'why'...
Do any of you have experience or knowledge of this spring type? And is it a good idea for a Z28/302 that I plan to rev towards 7000 rpm.... The company this shop uses is SBI (Nashville TN) for guides, valves, springs...   They will inistall whatever I want to pay for...   Any advice offered is welcomed.
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

Stingr69

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Re: New Valve Springs for '69 302...?
« Reply #1 on: March 25, 2009, 10:45:51 AM »
I put a set of those bee hive springs in my 302 and so far so good. The retainers are smaller so they weigh close to what a titanium retainer would weigh. PAC is the supplier I used for the springs. The retainers and locks came from Comp. It will run well over 7200 RPM without any issues and that is about where I chicken out. It would probably go higher. Crane F-278-2 cam runs very well in my otherwise close to stock 302.   :D

-Mark.

JohnZ

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Re: New Valve Springs for '69 302...?
« Reply #2 on: March 25, 2009, 06:30:23 PM »
The spring specs should be matched to the cam, and most aftermarket springs (including the "beehive" springs) are WAY stronger than the original stock springs. The beauty of the dynamics of the original Z/28 "30-30" cam "soft-action" lobe profile is that it used EXACTLY the same spring as all the 307/327/350 "grocery-getter" cars (P/N 3911068 single spring and damper - 90# closed, 190-200# open); Federal-Mogul #VS-677 is the same spring for less money.
'69 Z/28
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69Z28-RS

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Re: New Valve Springs for '69 302...?
« Reply #3 on: March 28, 2009, 03:18:02 PM »
I decided to go with the 'Z28 spring kit'..  as they appeared to be as original....
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

Jerry@CHP

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Re: New Valve Springs for '69 302...?
« Reply #4 on: March 30, 2009, 02:20:41 AM »
Good move, I use the conical springs in Stock Eliminator but we also use Shubeck lifters to mate with the camshaft.  We don't use conical springs in any of the stock 302 rebuilds that we do at CHP and still generate 335-370 hp in a stock rebuild with .040" head gaskets and conservative dyno.

Jerry

69Z28-RS

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Re: New Valve Springs for '69 302...?
« Reply #5 on: April 01, 2009, 08:53:46 PM »
Jerry, You indicated 0.040" head gaskets; so you are using the laminated head gasket versus the steel shim?  Are you doing this to reduce compression, or for some other reason?
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

Jerry@CHP

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Re: New Valve Springs for '69 302...?
« Reply #6 on: April 02, 2009, 02:01:19 AM »
To reduce compression and still use the factory correct pistons.......and make it run on pump gas.

Jerry