Need help picking valve springs
Thread Starter
Instructor
Joined: Mar 2021
Posts: 128
Likes: 29
From: Nashville TN
Need help picking valve springs
Long story short, just finished putting heads/cam/longtubes on my C5Z. On the dyno it fell flat on its face at 5500, peaking at only 408rwhp at 5700. LS6 peaks at 6k stock, so something's off. I'm running PAC 1218 springs with Yella Terra Ultralite 1.7s. I recognize this is a mistake, as its not nearly enough spring to manage the YTs. Cam Motion ground the cam and that was their assessment as well.
Cam specs: Cam Motion 222/250 .587/.579 133+3. They have given me 2 options:
1. Go back to stock rockers (with Trunion upgrade) and PAC 1219s, or 2) a good .660 lift dual spring and keep the YTs. Third option I think is obviously dual spring with OEM style rockers.
Thoughts? I've wanted to stick to a beehive because there's some school of thought that you want the lightest spring you can get away with for durability, etc. But I'm thinking maybe I overthought it (that's sort of a thing for me) and I just need to go with option 3 and be done with it.
Car will be mostly street/cruiser/fun with possible occasional HPDE.
TIA for the help.
Cam specs: Cam Motion 222/250 .587/.579 133+3. They have given me 2 options:
1. Go back to stock rockers (with Trunion upgrade) and PAC 1219s, or 2) a good .660 lift dual spring and keep the YTs. Third option I think is obviously dual spring with OEM style rockers.
Thoughts? I've wanted to stick to a beehive because there's some school of thought that you want the lightest spring you can get away with for durability, etc. But I'm thinking maybe I overthought it (that's sort of a thing for me) and I just need to go with option 3 and be done with it.
Car will be mostly street/cruiser/fun with possible occasional HPDE.
TIA for the help.
Race Director
Joined: Oct 2004
Posts: 12,864
Likes: 4,666
Long story short, just finished putting heads/cam/longtubes on my C5Z. On the dyno it fell flat on its face at 5500, peaking at only 408rwhp at 5700. LS6 peaks at 6k stock, so something's off. I'm running PAC 1218 springs with Yella Terra Ultralite 1.7s. I recognize this is a mistake, as its not nearly enough spring to manage the YTs. Cam Motion ground the cam and that was their assessment as well.
Cam specs: Cam Motion 222/250 .587/.579 133+3. They have given me 2 options:
1. Go back to stock rockers (with Trunion upgrade) and PAC 1219s, or 2) a good .660 lift dual spring and keep the YTs. Third option I think is obviously dual spring with OEM style rockers.
Thoughts? I've wanted to stick to a beehive because there's some school of thought that you want the lightest spring you can get away with for durability, etc. But I'm thinking maybe I overthought it (that's sort of a thing for me) and I just need to go with option 3 and be done with it.
Car will be mostly street/cruiser/fun with possible occasional HPDE.
TIA for the help.
Cam specs: Cam Motion 222/250 .587/.579 133+3. They have given me 2 options:
1. Go back to stock rockers (with Trunion upgrade) and PAC 1219s, or 2) a good .660 lift dual spring and keep the YTs. Third option I think is obviously dual spring with OEM style rockers.
Thoughts? I've wanted to stick to a beehive because there's some school of thought that you want the lightest spring you can get away with for durability, etc. But I'm thinking maybe I overthought it (that's sort of a thing for me) and I just need to go with option 3 and be done with it.
Car will be mostly street/cruiser/fun with possible occasional HPDE.
TIA for the help.
Le Mans Master
Joined: Oct 2007
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From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
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I too prefer the lightweight valvetrain. I would go with the BTR v2 trunnion upgrade on stock rockers and PAC 1219 springs. I run the stock rockers (stock trunnion) with PAC 1218 springs in my LS6 to 7400rpm no problem with stock cam. If I ever do a cam later on I will do stiffer springs and a trunnion upgrade.
Race Director
Joined: Oct 2004
Posts: 12,864
Likes: 4,666
To respond directly to you're question, I like dual springs over single. Probably in the minority on that one. Anyway-Best advice I can give you is to talk to someone at the cam grinder, AND at PAC. PAC makes some damn good springs. I've had PAC 1905 duals in my built LS7 for 8 years, 37,000+ miles!! I believe 1905 is too stiff for what you're doing. But give PAC AND the cam grinder a call. Who would know their products, and what is required, better than they do? 
Thread Starter
Instructor
Joined: Mar 2021
Posts: 128
Likes: 29
From: Nashville TN
To respond directly to you're question, I like dual springs over single. Probably in the minority on that one. Anyway-Best advice I can give you is to talk to someone at the cam grinder, AND at PAC. PAC makes some damn good springs. I've had PAC 1905 duals in my built LS7 for 8 years, 37,000+ miles!! I believe 1905 is too stiff for what you're doing. But give PAC AND the cam grinder a call. Who would know their products, and what is required, better than they do?
PAC says the 1218s are fine until 7k rom. After searching LS1tech extensively I've found several folks running 1218s with similar cams and spinning to 6600, 6800, even one to 7500! Also, the Sloppy Stage 2 and WS6store hot cam kits (both similarly spec'd) come with 1218s.
So I think I am going to at least try OE rockers and leave the 1218s in there, at least for another dyno session. May still swap them out for peace of mind of a dual spring, but trying to trust the opinion of the spring manufacturer and not overthink it for once LOL.
