I'm wondering if anyone has tried the Harland Sharp 1.8 rockers, because they would be perfect to get a little more lift out of my low lift (.510) cam. I've contacted Lunati about this and they are discouraging me due to the increased possibility of valve float. From what I understand valve float is primarily created by the pushrod flexing under load and springing energy back out. It would seem a quality set of hardened pushrods would solve this problem but Lunati also said they didn't recommend using 1.8 ratio rockers with hydraulic lifters. Does anyone know how much these OEM lifters can handle? The load on the lifter would only be increased by less than 6% according to my calculations so I'm wondering how much of a problem it could be.

And no I DON'T want to change my cam, I just would like to get a little more out of this one when I upgrade my valvetrain. Thanks for any input on this matter.

 

I would avoid the Harland Sharp or Yella Terra rockers,I've heard that they gave problems.You could benefit from more lift,but Lunati knows what works well with their profiles,so I would swap cams if I wanted more lift.The 1.85 ratio would accelarate the ramps on Lunati's cam profile causing early valve float.Cams with identical timing specs can have radically different ramp speeds so one manufacturer might recomend the use of 1.85 rockers while another says no,because they know from experience what will work.

 

Thanks whitt, I think I'm going to stay away from those and I'm now leaning towards the Vinci accelerated lift 1.8. Want to bump this up again and see if anyone else has an opinion on it because I am feeling Lunati's response was the just the safest being that I'm using one of their smallest LS1 cams.

 

I just put some HS 1,8's on my truck , replacing yella Terra 1.7s, for the sole purpose of a little mor lift, with the small 206/212 comp already in it. I like it so far. I know it would be better to just have a bigger cam but I really did not feel like the hastle again. I have had no problems at all with Yella rockers. They are WELL built. I have done machinist work before and The yella Terra's are well crafted.We will see about the HS rockers. So far I am pleased with them.

 

Thanks for your response. What was the lift on your cam?

The F-body guys are saying that the 1.8's shouldn't be a problem with a good set of springs. I'm thinking of going with the Vinci/Crane rockers because the design would seem to yield a little more hp, not to mention there are plenty of sets to be had used.

 

.515/.522
I think the cranes are nice too, I just found a better price on the sharp's.

 

You've got you explaination of valve float mixed up. It's not because of pushrod flex, but because the springs aren't strong enough to slam the valves back closed again before the cam tells the valve it's time to open up all over again. When that happens the valves doesn't know whether it's supposed to be open or closed at any given point in time and this condition is called "Valve Float". It only happens at high RPM when the time interval between closing and opening up again is very small. I've been running Comp 1.85 Pro Mags on one of my Silverados for years. They're great! Not cheap, but very reliable. A little noisy when you first start the engine after installing them, but they quiet down after a few minutes. I use Comp R lifters with them and if you do set them to zero lash and then tighten the polylocks. Don't add any extra preload with the R lifters.

 

Yes I understand too little spring pressure also causes float but the pushrod thing comes from Crane's literature somewhere. I think that they were trying to dispell a myth about the rockers absorbing energy then springing back to shape contributing to valve float.

 

Can you imagine rockers and pushrods especially hardened ones flexing or bend under load while the engine is running absorbing energy resulting in valve float. You'd have to own a really high speed camera to film something like that taking place. I don't buy it. If it does happen the effect has got to be miniscule compared to that of what results from weak springs.

 

every metal, even hardend pushrods, have a certain point of elasticity and up until that point they will bend but return to their previous shape. bent pushrods come from when the pushrods go past the elastic point... so i definately believe it is possible.