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Old 09-06-2003, 03:14 PM
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replacing valve springs

I did some searching in the knowledge base but didn't find much, so I'll ask it here. I am replacing the stock valve springs in a 350sbc to .500 lift Z-28 springs. What do I need to do after replacing them? I have heard people talking about spring height. What do I need to do or look for when changing them out?

TIA!


Forgot to mention that it has pressed in studs. Will it require screw in studs?
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Old 09-06-2003, 03:28 PM
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You can get by with the studs if you run no more than a 488 lift cam , i have seen more like 500 max but you will have problems sooner or later.
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Old 09-06-2003, 04:02 PM
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The cam I am getting is a Comp. Cams 4x4 Xtreme 250/258 duration, 206/214 @ 50 and .432/.453 lift. So, the max lift will only be about .453.
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Old 09-06-2003, 04:18 PM
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Are the heads on or off?
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Old 09-06-2003, 04:19 PM
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Your valve springs are rated at a certain amount of pressure at a specific installed height. If you remove the springs from your heads, put a valve back in it, install a retainer and the keepers for that particular valve, you can measure from the retainer (where the valve spring coil would sit) down to the spring pocket on the head and this would be the dimension at which the spring would install at.
Most Z-28 type springs will install at 1.750" so if your dimension was more than that, you will need to add shims to obtain the desired installed height. The term "Z-28" springs is a widely used term and there are plenty of performance type springs that install at 1.800" so be sure to check your manufacturer's specs on your particular springs. One word of caution, DO NOT install your springs too tight and exceed 120 lbs of seat pressure with a hydraulic cam, as you will be inviting premature camshaft lobe wear.
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Old 09-06-2003, 04:24 PM
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The heads are sitting on my bench waiting for assembly. I have all the parts, just haven't done it yet. How can I check what pressure it is? From what I've seen and heard, you compress the spring and install the keepers and they keep it in place.
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Old 09-06-2003, 09:09 PM
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NAIRB outlined how to measure valve height. When you bought the springs there should have been some information with them that stated the installed height, seat pressure, coil bind height, and open pressure. If they are brand name, you can go to their web site and find out that info if you don't have it.
Most Chevy valves I've used install at 1.7" or 1.75". A cheap way to check the retainer height is to cut a piece of coat hanger to the desired height length. You can then use it to check each valve.
When you put the valve in, you place the spring in its pocket and place the retainer on top. Compress the spring and retainer, and place the oil seal (o-ring) in the second groove of the valve. Then put your keepers on and release the valve compressor. If you're using umbrella oil seals, you'd put them on over the valve stem before you put the spring on. I use both o-rings and umbrellas.
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Old 09-06-2003, 09:23 PM
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I checked on the info you said and it shows 1.75 for height and 110lbs for pressure. The springs installed are right at 1.75 with everything in place.
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Old 09-06-2003, 10:46 PM
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Sounds like you're ready to rock'n'roll.
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