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 suggestions:

1. Go back to stock rockers (with Trunion upgrade) and PAC 1219s, or 2) a good .660 lift dual spring/Ti Retainers and keep the YTs.

I think a third option is dual springs/Ti retainers 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.

 

Hey there, maybe this will help...

Lighter springs do not correlate to durability. Springs have to control their own weight as well as the other parts in the system. Lighter springs reduce valve float, assuming there is enough spring pressure to control the valve, the rockers, etc... Also, I've driven engines with very light valve springs. They rev really quick. Very snappy, if that makes sense.

At .580 lift, I would generally stay with stock style rockers, and I'd run a psi 1516 single valve spring, shimmed up .075", assuming a 1.100" coil bind and 1.800 installed height. That would be my first choice. For the YT's if you decide to keep them, I would go to PAC 1207X and also shim up .075" for some added seat pressure.

If you don't have it in the list yet, add a set of 5/16 x .080 pushrods.

 

Thanks, that helps a bunch. Set of chromoly 5/16 .080 pushrods already in the car. I think I'm going to let the YTs go....simply overkill for my application. I was going for durability but there's too many people running OE style rockers w/o issues for this to be a real concern (especially under .600 lift).

 

If you are going back to stock rockers, there is zero need to change springs.

 

You think the 1218s are OK with OE rockers and that cam?

 

I hope that 133 degree lobe separation angle is a typo.

 

sorry, yes. 113.

 

Yes I do, unless you plan on spinning over ~7200 RPM.

 

Nope, 65/6600 at most.

 

You have more cam than that... 7000 easy.

 

You have more cam than that... 7000 easy.

 

If that's the case, then I think duals and Ti retainers are the better choice.

Looking at the BTR .660 platinums...they seem to have a tad less seat and open pressure vs e.g. the PAC .660 springs. With OE rockers that shoudl be a good compromise in weight v. valve control/load.

 

Listen to TurboBuick6. He works for PAC tech and knows what he’s talking about.

 

Thanks for that tidbit. It's certainly worth a shot..can always change the springs later if needed. Trunion-upgraded OE rockers already on the way.

 

If you are selling those YT's shoot me a PM.

 

The 133 LSA was a typo … what about the 222/250 duration? I’ve never seen a split that large …

 

Also a typo. Man, I must have been in a hurry. Its 222/230.

 

What does Cam Motion recommend? I have a Cam Motion .600 lift cam, running PAC 1905 dual springs/Ti retainers, good for .650" lift. Regardless, one thing you need to watch is how much lift vs spring installed height. To exaggerate, you wouldn't want to have a .400" lift cam with dual springs rated for .700" lift!! Reason being you don't want too much free space/too many coils, because this can lead to a lot of spring surge, which amounts to a lot of coils acting like a Slinky!! Premature spring failure. I agree with Che70velle, that TurboBuick6 knows his stuff. He works at PAC. Met him once at the factory. Very knowledgeable, nice guy. If youre not going to check with Cam Motion, I'd listen to him.......

 

Cam Motion recommended pac 1219s with OE rockers or a .660 dual with the YTs.