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Old 12-04-2007, 02:49 PM   #1
vfr_rider
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Member#: 155173
Join Date: Jul 2007
Default do i need springs?

i am looking to up grade my cams to Adv. Dur.Dur @ .050Lift (in)Lift (mm)Kit #Street/Strip Specification


114272/272220/220.400"/.400"10.16/10.16
will i need to get better valve springs or will the stock springs be ok? thanks for the help.
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Old 12-04-2007, 03:41 PM   #2
wcbjr
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2006 Legacy GT
Obsidian black

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Whoever made the cam should tell you. If they cant tell you, dont buy the cam from them.
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Old 12-04-2007, 03:53 PM   #3
03cinwgn
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I agree, just double check and make sure your stock springs are adjusted correctly to the correct tension and your seals dont have an visible wear around them if you are able or ask the shop that is installing them too, but its not a bad idea cause u gotta factor in longer intake and exhaust valve duration. make sure is you get new springs to get new seals. its a u do one u might as well do the other deal.
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Old 12-04-2007, 05:13 PM   #4
vfr_rider
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Default what

im installing them, I built my short block last year and i am tring to stay away from having to take it out and replace valves and spings. (lazzy) i just wonted to know if the valves are going to float.
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Old 12-05-2007, 09:23 AM   #5
wcbjr
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Just shim the springs more.





Just kidding.
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Old 12-05-2007, 11:20 AM   #6
BallPeenHamr
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2007 STi Limited
#339 UGM

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Quote:
Originally Posted by 03cinwgn View Post
I agree, just double check and make sure your stock springs are adjusted correctly to the correct tension and your seals dont have an visible wear around them if you are able or ask the shop that is installing them too, but its not a bad idea cause u gotta factor in longer intake and exhaust valve duration. make sure is you get new springs to get new seals. its a u do one u might as well do the other deal.
I know you mean well in helping out a fellow nasioc brother. But you are incorrect in more ways than one... sorry to call you out.

a) Springs are not adjustable, and tension is not a characteristic of valve springs. However, the pressure is adjustable by means of spring shims.

b) You cannot see if your stem seals are bad by looking at them in the head. Just get new ones... they're cheap, and the heads will be appart anyway. Your main focus here should be excessive guide wear. Have the shop check it.

c) More valve duration (should be "cam duration") will not determine if you're springs are suitable for your application. However, Valve lift will. With a higher lift cam, you run the risk of coil binding the spring... which means your valve spring fully compresses before the cam opens the valve to full lift.


To the OP, my advice: Get new "drop in" aftermarket springs to directly replace your stockers that will acomidate higher lift cams. Do some research and pick a brand within your budget that others are using... they should be fine. Don't bother with shimming, and don't be concerned with spring pressures because aftermarket springs will give you a lil bit more of that anyway... and your not getting a valve job. Valve float? Just keep it below 8.5k rpm for 2.0L, 7.5k for 2.5L and you'll be fine with aftermarket springs. Buy new stem seals cuz they're cheap and they'll help keep the oil where it should be. Most importantly, have the shop mock up the cams in the heads and recheck the cam lash....it's the gap between the cam base circle and the tops of the buckets.

Have fun and good luck.
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