I own a 2004 Z06 LS6 and am considering installing a 1.85 ratio rocker arm set to replace the stock 1.7 ratio set.
Does anyone have exeperience with this installation?.
If so, how does it affect the low end torque, the horsepower and the idle smoothness?
Thanks,
Gary Sacco

 

not worth the 5-7hp.

 

check out crane cams quick lift rocker arms.

 

The Cranes are the only rockers I am aware of that provide a different rocker ratio arc. They start out higher and then the ratio reduces to the prescribed ratio (in other words, the 1.8 rockers open the valve at 1.89 and by 0.300" lift the ratio is down to 1.82.) Stock rockers come off the seat at 1.54 and are barely at 1.7 by full open. Stock rockers also have a crappy wipe pattern, I could not get a narrow centered wipe pattern when I set up my Dart heads with the stock rockers.

David Vizard discusses off the seat valve acceleration in his article in Popular Hotrodding, it is on the Popular Hotrodding web site and is called "Be the Cam Expert".

All rockers are not created equal, if you are trying to use them for a power increase you need to research how the rockers open the valve and how the ratio's work. There is no such thing as a "constant ratio", all rockers change ratio during valve operation.

 

Harland Sharp also make the 1.85 ratio rockers.

 

Will not really affect idle at all because lsa will be the same. Crane claims about 20 horsepower, some probably coming from the better vavle springs on top end im sure. Installation is no problem. When you do springs I would reccomend not pulling the heads and using one of cranes new springs tools or comparable not the old crappy ones with a 2' handle. Personally I would replace springs even if I didnt do rocker arms Just to get rid of the crappy design

 

Do you mean the beehive design? Not sure I follow the logic.

 

yes beehives are a pretty crappy design.

 

Very Loud springs, and lose alot of seat pressure quickly.

 

Can't say that I agree. I ran the Crane dual 832's and had harmonic issues, now have PSI beehives. I was concerned with the beehive design, but they have shown themselves to be lighter with negligable harmonics due to the non-linear stiffness characteristics. The Comp 918's don't lose hardly any preload.

Here is the article written by David Vizard. Beehives have proven themselves on big blocks, Fords and NASCAR.

David Vizard's Beehive Spring Article

 

He already has behive springs, as all LS2/LS6s do.
If forget what the lift is on a stock LS6 cam, but divide it by 1.7 then multiply it buy 1.85, if the new total lift is below 560-ish, you are good with the springs you have. If it is more you will need to upgrade your valve springs, Comp 918s are the usual way to go, will swap right into your current valve seats, locks, retainers.

You will need to be able to adjust your new rockers to zero lash, that is fairly easy. If you do not have at least some shorty headers I would not bother with it. You won't get your benefit with the stock exhaust manifold. However if you do I think they are worth it.

I have the Comp pro-magnums which I like the best for design and durability, however you will need to modify your valve covers so they dont hit them. Easily done, but a pain. See pic at bottom of main page in my website in sig.

Reportedly both the Crane's and SLPs do not require valve cover modification. Go with the Crane's, they have gotten good reviews, while the SLPs seem to get the most negative reviews for power.

Also be a good time to get a decent dyno tune when you are done, to take full advantage.

I remember the pull up through third gear (when I still had 3.42s) got real exciting after that swap.

Not an expert, just my $.02, hope it helps.... Good Luck!

 

I'm not a fan of really any of the rockers available except the lightweight T & D and Jesel. Almost all of them add weight over the nose of the rocker which is bad for valvetrain stability. A few brands use guideplates which IMO is old technology.

 

I will agree beehive are definetly lighter however nothing I cant do with ti retainers and locks. But from personal experience they definitely lose alot of seat pressure fast. More food for thought, Everybody seems to think less spring pressure more power because less friction including that article you cited, however just remeber when the motor compresses a spring eventually the spring will be allowed to pushed itself back up, allowing the energy put into the spring to come back out helping to turn the camshaft. I think it was crane who ran tests on this and concluded there is negligible horsepower loss from too much tension on springs. This is what crane says about beehives, But just the same as your page im sure it is a biased opinion. Would be interesting to see what an independent lab would turn up.
http://www.cranecams.com/?show=newProduct&id=14

 

I think one of the points in the article is that you end up with lighter parts all the way around (assuming the same valve) and limited or no harmonics, which a dual needs to have a much higher spring rate to achieve. For example, my PSI springs are 66 grams and the retainers are 6.6 grams. I have my Cranes in the basement, but unfortunately they are still on the heads. I am willing to bet the retainer alone is 12 grams or more, even though it is titanium.

As for noise, I didn't have any knock retard issues with the beehives nor are they any noisier than the Cranes were that I had previously.

 

Several guys operating C6's have reported good results with the SLP 1.85's. They are getting close to 20RWHP/20RWT. I have the Crane 1.8's on my C6 with the 832 springs, larger pushrods and TI retainers. I have no power dips out to 6,600 or any other issues. I didn't do my dyno before and after the rocker change so I can't really say what it did. I could feel it though, so it had to have been more that 10RWHP. I have been operating these now for 4,500 miles.

 

Great article, thanks! I'm familiar with Dave V.'s writings for over 20 years now, glad to see he didn't retire!

Makes my 918's w/ Ti retainer choice all the better; I knew I did not want to stray from the factory beehive design.

 

Well, since GM used beehive springs on every single LS1, LS6 and now LS2 motor in production, I think they would tend to disagree with your statement.

 

This INFO will come in very handy one day SOOOON!!!

BC

 

Well, thought I would put this one out there as well. This is one of the latest of David Vizard's writings, very nice write-up and captures some of the information in his books. Also note his discussion on rocker arm lift off the seat.

David Vizard's Cam Article