CRG Discussion Forum
Camaro Research Group Discussion => General Discussion => Topic started by: 69Z28-RS on March 24, 2009, 04:50:10 PM
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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.
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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.
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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.
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I decided to go with the 'Z28 spring kit'.. as they appeared to be as original....
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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
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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?
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To reduce compression and still use the factory correct pistons.......and make it run on pump gas.
Jerry