jmproductions

Thought I'd come over to the car section and post this since you guys know a lot about valvetrain combos on these engines. Here it goes:

I'm thinking about trying the 1.8 Vinci Accelerated lift rockers (Crane Gold Race quick lift), because they should be perfect to get a little more out of my low lift (Lunati 212/221 @ .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/upgraded springs would solve this problem but Lunati also said they didn't recommend using 1.8 ratio rockers with hydraulic lifters. Has anyone had any problems using the OEM lifters with these rockers? Or what about these rockers on non-Vinci aftermarket cams? 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.

I'm not really interested in changing cams right now I just want to get a little more hp while upgrading valvetrain.

mrr23

iTrader: (3)

it's not a problem. ran the vinci/crane kit for well over a year on the stock cam and lifters. then, put the vinci 062 cam 210/218 .551/.551 in with same stock lifters. still no issues. so long as you have proper piston to valve clearances and proper spring pressure, you are good to go.

the vinci/crane 1.8 rocler kit comes with rockers, pushrods (have to use shorter than stock), guideplates, screw-in-studs, and posilocks. $699.00 on www.vincihighperformance.com site

jmproductions

Yeah I like that kit, that's the one I'm looking at. I figure at this duration I should be no where near P/V clearance issues and at .540 calculated total lift the LS6 springs should be enough.

mrr23

iTrader: (3)

it will be .546 with the accelerated lift rockers. the peak lift with the rockers is 1.82. they come off the seat at about 1.89, then about .250 lift, they start converting to 1.82. then revert back to 1.89 on the way down at the .250 lift area.

mrr23

iTrader: (3)

i was at .589 lift on the 210/218. so, i don't forsee a p to v issue either.

jmproductions

That's good info, thanks!

vettenuts

iTrader: (4)

I know someone running an XER Comp cam with the Crane 1.8 rockers, it all comes down to the valve springs. He was using the 918's, not sure what he is using now because he just went to a bigger cam, same rockers though

jmproductions

Does anyone think the LS6 springs won't be enough on my setup?

vettenuts

iTrader: (4)

Which retainers?

Tony Mamo @ AFR

iTrader: (13)

The stock LS6 springs will be "dicey" with that set-up. You should consider upgrading to the Crane dual spring, a 918 or 921 Comp, or another lightweight quality dual spring which has more seat and over the nose pressures. The higher rocker ratio and increased mass of the aftermarket rocker arms need more spring pressure for accurate valve control. The quicker valve motion and additional lift utilizing your current cam profile will probably net you some small gains and increased response, but if you plan on turning it much over 5500 RPM's, I would ditch the LS6 valve spring set-up....it was designed for much lighter valvetrain components that were factory installed on the LS6 engines.

The Crane rockers are excellent, but the proper set-up is critical to get the most benefit from their installation and never put the higher rocker ratio stuff on some of the faster higher lift lobes that are more commonplace. Valvefloat is almost guarantee'd....better performance and reliability is achieved sticking with the 1.7 ratio stuff which is really closer to 1.73 if you were to actually check it

Just my .02 here....

Tony M.

jmproductions

Well I'm still making power above 6000 now on the stock springs, remember this is a 4.8, so maybe something better than LS6 springs is needed. It just seems like 918's on .546 lift is a little overkill but if that's the safer way to go, ok.

vettenuts

iTrader: (4)

Don't forget, the lift off the cam is at almost a 2:1 ratio with the 1.8's. Since you have the LS6 springs, the 918's might work.

Spinmonster

I have run a xer 224 230 .581/.592 114 lsa cam with them now for about 3 weeks with no issues. Springs are crane 832's shimmed to 1.74 install height. The peak lift doesnt cause p/v interference, its a function of duration and lsa. Youre cam is tiny and will work fine but you need a good dual spring. Use crane 832's and use a .030 shim under the hardened seat. It will work fine. I have 2 sets of those rockers for sale if you are interested.

I have to disagree with you Tony, if you have enough spring, any ramp rate would be fine but LSK lobes would be too much lift and would probably run into problems.

jmproductions

No right now I'm actually on the stock 4.8 springs!

Tony Mamo @ AFR

iTrader: (13)

Real world results as well as SpinTron testing would prove otherwise (based on a reliable source at Comp)....I don't think you could find one guy on this board with XER lobes and aftermarket 1.8 or higher ratio rockers that is putting down big numbers with clean dyno graghs up to 7K....and I have seen a handful of guys swap rockers in the other direction that have tried.

I would be interested to learn more about the set-up of someone who might have gotten away with it....

Tony M.

jmproductions

Ok guys so what do you think is my most economicable spring choice? 918's? I don't need to overspring it because I will not be changing cams in this engine, if I decide I need more later I'm pulling the little 4.8 out.

Asmodeus

You don't understand valve float. It has nothing to do with pushrods. Valve float is what happens when the spring cannot control the valve. This is due to inadequate spring pressure. The rockers will increase the speed of the valve, thus the concern for possibly bringing valve float into the picture.

vettenuts

iTrader: (4)

I personally think the 918's would do the trick, they are lighter from an accelerated mass standpoint as well. The cam you have isn't huge. Since they are beehive, they will fit without new seals too. If you go the double route, you will need to install new seals (assuming you have the 02+ integral seal/seat setup). I am also assuming you don't spin much over the stock rev limiter with that cam.

jmproductions

Actually I think that pushrod flexing thing came right from Crane's literature somewhere, but yes that leads to the valve pushing away from the valvetrain resulting in separation. I do understand that the same thing happens without enough spring pressure also.

So anyone else agree that 918's will do the trick? I want the valvetrain to be stable until at least 6400.

jmproductions

So here's the pressures that I have calculated for my setup on some of the springs we've been discussing. Listed first is the seat and then open to .546

Comp 921: 135, 357
Comp 918: 130, 301
Crane 832: 112, 304
Crane 832(+.030): 123, 314
OEM LS6: 100?, 272

Some of the specs are pretty similar so which of these springs would require the least amount of hassle/extra parts to install on my 2001 4.8/5.3 heads?