Need Help - Valve spring ?
09-15-2007, 10:37 PM
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Need Help - Valve spring ? My brother had his stock heads ported/polished/milled by a local race shop on his 81 camaro 350 small block a few years ago. He doesn't remember anything regarding valve springs except that they were replaced. Currently we are running a fairly mild cam 292/292 low .5xx lift with 11:1 domed pistons. I am about to install a bigger cam with an advertised duration of 322/312 and a lift of .533/.555. Is there a way to determine what lift the valve spring is capable of handling just by pulling a valve cover?
09-15-2007, 11:54 PM
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The right way to do it---just replace them, they're a couple years old and not matched to the cam.
Budget way to do it---get the recommended spring specs, take a few springs off, take them to an automotive machine shop and have them test the pressure at different compressed heights.
Budget way to do it---get the recommended spring specs, take a few springs off, take them to an automotive machine shop and have them test the pressure at different compressed heights.
09-16-2007, 12:29 AM
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any cam with a lift over .505, the heads will need machine work. what they do is mill out the spring pocket which makes the spring sit lower to compensate for the higher lift. make sure you check that or else you will end up with a flat cam. call a couple machine shops around you and ask them.
09-16-2007, 03:39 PM
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You are going to want to get a spring that has about 110-120 lbs on the seat and 300-320 lbs of open pressure to reliably handle the demands of that cam. As mentioned before you are going to have to have the spring pockets modified, valve guide's cut down (for the increased lift), and be machined for screw in studs & guide plates.
09-18-2007, 04:22 PM
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play it safe and get new springs. comp 918 beehives for 189 bucks will handle any cam under 600 lift. its the BEST bet in springs for that setup and will fit stock pockets i do believe as the spring is 1.29 inch diameter i think at the base. you'll have to see.
else definately try to get something with pressures as mentioned above. And something that can handle .555 lift. Most single springs at installed height of 1.75" or so can only handle .550 safely so you'll be on the borderline with .550.
get screw in studs for sure
you probly willl have to cut down the guide bosses to as retainer to guide boss clearance usually bottoms out at .480 lift or so. even .050 offset locks and .050" of shims will raise that clearance to .530" lift which is still not enough for that motor.
else definately try to get something with pressures as mentioned above. And something that can handle .555 lift. Most single springs at installed height of 1.75" or so can only handle .550 safely so you'll be on the borderline with .550.
get screw in studs for sure
you probly willl have to cut down the guide bosses to as retainer to guide boss clearance usually bottoms out at .480 lift or so. even .050 offset locks and .050" of shims will raise that clearance to .530" lift which is still not enough for that motor.
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09-18-2007, 06:04 PM
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Originally Posted by Orr89rocz
play it safe and get new springs. comp 918 beehives for 189 bucks will handle any cam under 600 lift. its the BEST bet in springs for that setup and will fit stock pockets i do believe as the spring is 1.29 inch diameter i think at the base. you'll have to see.
else definately try to get something with pressures as mentioned above. And something that can handle .555 lift. Most single springs at installed height of 1.75" or so can only handle .550 safely so you'll be on the borderline with .550.
get screw in studs for sure
you probly willl have to cut down the guide bosses to as retainer to guide boss clearance usually bottoms out at .480 lift or so. even .050 offset locks and .050" of shims will raise that clearance to .530" lift which is still not enough for that motor.
else definately try to get something with pressures as mentioned above. And something that can handle .555 lift. Most single springs at installed height of 1.75" or so can only handle .550 safely so you'll be on the borderline with .550.
get screw in studs for sure
you probly willl have to cut down the guide bosses to as retainer to guide boss clearance usually bottoms out at .480 lift or so. even .050 offset locks and .050" of shims will raise that clearance to .530" lift which is still not enough for that motor.
