PRC dual valve spring broke
running a set of performance valve springs on the street longer than 10k miles is stupid. ***** not made to last 150k miles like the stock ones. Just because of the cam profile, you have that spring keeping track of a heavy *** valve which makes the spring work hard. weather or not its a .550 lift cam or a .650 lift. heavy valves work the valve spring harder.
I went with Manley hollow stem intake valves with manley nextek double springs on my L92's. Zero problems and I rev it to 8k with stock rocker arms. Springs have 6k miles on them, and guess what. They needed replaced. BUT I could never tell it...
I went with Manley hollow stem intake valves with manley nextek double springs on my L92's. Zero problems and I rev it to 8k with stock rocker arms. Springs have 6k miles on them, and guess what. They needed replaced. BUT I could never tell it...
Launching!
Joined: Feb 2004
Posts: 260
Likes: 0
.550" valve lift,
Is a whole lot easier on the whole of the valve-train, let alone the springs; than .600+ would be.
GM validated the '02 LS6 cam with a full warranty using .550 v-lift and 260lb beehive springs.
C-C Tech people reckoned when asked directly, that .570 lift with XER lobes needed v-spring changes every 30,000 miles.
IMO if you're going above .580 you are into regular spring & lifter changes and much lower intervals than 30k.
Is a whole lot easier on the whole of the valve-train, let alone the springs; than .600+ would be.
GM validated the '02 LS6 cam with a full warranty using .550 v-lift and 260lb beehive springs.
C-C Tech people reckoned when asked directly, that .570 lift with XER lobes needed v-spring changes every 30,000 miles.
IMO if you're going above .580 you are into regular spring & lifter changes and much lower intervals than 30k.
TECH Apprentice
Joined: Jan 2008
Posts: 366
Likes: 0
From: Gladstone, Queensland, Australia
I'd say there is some valve float there going on, instability of valve due to lack of spring pressure. I would be going the PAC 1521s to get better life from the spring and less harmonics and thrust movement on the guide. Depends on how hard you rev it but LS3 valves are a good idea.
I think the whole valve instability thing occurs in a lot of engines and people ignore it or don't know what is happening. As already pointed out the springs can lose pressure as little as 6000 miles when driven hard and it doesn't surprise me with heavy valves. More spring pressure is the way to cure it.(unless you want to change your springs more) I am unsure of the PRC spring quality but at 20000 miles they would be so great. My patriot extremes have surpassed 15000 miles with zero float and no sign of it inspecting the head. The springs also test fine, I am now near 20000 miles and I feel its starting to float a little with the cam I am using(more aggressive). Using more seat pressure cures this. 160 pound isn't that much really compared to what most performance solid roller setups run ie 200 and some. They are exy too, but I bet the springs will still be good at 20000 miles. Cheap insurance. Any of the springs on the market are good including the 1518s which are brilliant and most probably control the valve better at 7000rpm then the bottom range duals hence no valve float and rotation and no excessive guide wear or valve stem breakage.
Best thing is to run a decent spring and change them on the correct interval. Maybe check them at 10000 miles and see how they look and replace at 15000.
I think the whole valve instability thing occurs in a lot of engines and people ignore it or don't know what is happening. As already pointed out the springs can lose pressure as little as 6000 miles when driven hard and it doesn't surprise me with heavy valves. More spring pressure is the way to cure it.(unless you want to change your springs more) I am unsure of the PRC spring quality but at 20000 miles they would be so great. My patriot extremes have surpassed 15000 miles with zero float and no sign of it inspecting the head. The springs also test fine, I am now near 20000 miles and I feel its starting to float a little with the cam I am using(more aggressive). Using more seat pressure cures this. 160 pound isn't that much really compared to what most performance solid roller setups run ie 200 and some. They are exy too, but I bet the springs will still be good at 20000 miles. Cheap insurance. Any of the springs on the market are good including the 1518s which are brilliant and most probably control the valve better at 7000rpm then the bottom range duals hence no valve float and rotation and no excessive guide wear or valve stem breakage.
Best thing is to run a decent spring and change them on the correct interval. Maybe check them at 10000 miles and see how they look and replace at 15000.
Last edited by hymey; Feb 13, 2010 at 08:02 AM.
TECH Apprentice
Joined: Jan 2008
Posts: 366
Likes: 0
From: Gladstone, Queensland, Australia
My extremes have been in for 20K and had nothing but xfi lobes on them. I am replacing them just for the sake of maintenance and there cheap. I have not checked there pressure, but it is definately getting a little fade at 7200rpm which isnt to bad as I normally only spin it to 6800-7000, the extremes are great and I will keep them in there as I have not had any issues with them.
A guy on GTO board got 50000 miles on extremes and lost 5 pound at the seat with a V3 cam on 640 plus lift. I don't know why they are bagged out, possibly a sponsor advertisement thing I guess.
I just think they should be changed regularly as basically there consumables. And its preventative maintenance. If they are changed at 75% of there life span at least they will always have decent pressure and minimal float issues. If they are changed once they start to lose excessive pressure, then things can go horribly wrong. Its the only part that really needs to be changed every 15000 miles or so. Just think 30 to 40 years ago heads were coming off that often to lap valves. If a simple spring swap on a fixed basis prevents damage and improves performance it is worth it.
A guy on GTO board got 50000 miles on extremes and lost 5 pound at the seat with a V3 cam on 640 plus lift. I don't know why they are bagged out, possibly a sponsor advertisement thing I guess.
I just think they should be changed regularly as basically there consumables. And its preventative maintenance. If they are changed at 75% of there life span at least they will always have decent pressure and minimal float issues. If they are changed once they start to lose excessive pressure, then things can go horribly wrong. Its the only part that really needs to be changed every 15000 miles or so. Just think 30 to 40 years ago heads were coming off that often to lap valves. If a simple spring swap on a fixed basis prevents damage and improves performance it is worth it.
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Like every one else posted you should run the lite weight valves with a 1221 or a 1521 spring. I bought a set 1518's and Ed Curtis of FTI said that they were not enough spring to control the 2.165 valves. The exhaust side is not as much of a problem. Being FI I would run a inconel exhaust valve. I bought REV valves. The stock LS3 valves are nice pieces and they are hollow on the intake side.
