Wow... now that's really interesting that you gained that much with a stock ratio rocker. I'm intrigued... do you think there'd be that kind of benefit for someone running a cam like mine with your 1.7 rockers?

My cam's stats at .050 are: 231/237 .598/.598, 112 LSA. I'm running Patriot Gold Dual springs which are good to .650 on the lift... it's also a Lunati grind, so the lobes are less aggressive than say that of a Comp XE-R.

 

Marc,

Yes it is true because at any point in the lift curve the rocker ratio increase is accelerating the lift of the valve more than what the cam lobe alone can do. It's simple geometry. The only problem with higher ratio rockers is that you are putting the valve back on the seat harder. This is where you would like to run valve springs that can be shimmed to a relatively high seat pressure to keep the valve from bouncing, but has a moderate rate to minimize pushrod deflection and uncontrolled valve lofting. This is exactly why our 144832 springs are designed the way they are!

Also, higher ratios provide more lift at the valve. With the stock pistons we don't recommend more than .585 valve lift unless you carefully check Piston to Valve clearance. Hope this helps!!

Mark

 

Read some of the posts above. I'm quite confident of our rockers. Our chief rocker arm engineer is Ralph Johnson. He is one of 12 people recognized by Performance Racing Industry (PRI) as being most important in the development of the SBC. He was friends and working partner of Smokey Yunick for over 40 years and did much of Smokey's rocker arm and valve train work. He is the man who has developed our new composite matrix shaft mounts for all out competion. Ralph designed our LS1 rockers and they were tested by Ralph with the cooperation of Vinci High Performance. Ralph isn't interested in the everyday "Joe" knowing who he is and what he has done, but believe me, the big guys in every type of racing know Ralph and what he can do. There is a lot of subtlety in rocker arm design. Our rockers work and they also fit the LS1 without trimming to clear the valve covers. They provide full adjustment for preload. They are extremely quiet and don't cause false KR. Some people on this site think aftermarket rockers aren't as strong as stock. At Crane we have a fixture to test rocker deflection and strength. The figures in this test do not relate to valve spring loads but DO relate to ultimate rocker strength. Stock rockers fail our test by bending at 2100# and breaking at 2300# . Our rockers hold solid till 3400# and break at 3500#. As I said a little earlier, they cost a little more than others, but they flat work!! Incidently, for anyone attending the PRI Show in Indianapolis this year, I will be giving a one hour seminar Friday morning on Quick-Lift Geometry and using the rocker arm ratio to augment cam lift rates. It's free and you all are invited!!!

Mark Campbell

 

My cam specs with 1.7's and stock LS1 heads:

Intake 280 seat duration, 224@.050,.569 lift.
Exhaust 286 seat duration, 228@.50, .561 lift.
112 lsa, 108 lc.

My cam specs with 1.8 CRANE rockers and AFR 225 heads:

Intake 280 seat duration, 226@.050?, .603 lift.
Exhaust 286 seat duration, 230@.050?, .594 lift.
112 lsa, 108 lc.

To take advantage of the AFR 205 or 225's high valvelift flow numbers I can simply add the CRANE 1.8 rockers without having to go inside the motor and exchaging and degreeing cam. This is one major advantage of the roller tipped 1.8's. HELL YES !!!

 

my fault. i must've missed the detrimental post.

 

Thank you very much for your generous offer, Mark. I'll be in contact with you upon your return.

 

Not a problem. I make mistakes on a regular basis.

 

Mark Campbell

Hi there: I am on the fence about the rockers so I have a few questions.
There are some here that claim the H.S. rockers cause float at around 5g rpm, any float with crane if so what springs do you suggest. Does crane have beehive springs to go with the rockers? I am not going to put a cam in my car I want to keep the heads cam and cast manifolds and hopefully get into the 11sec club with an 11.99. However, I will need 1.8 rockers to get there and I am wondering what kind or rwhp I could expect to see. I currently have 336 rwhp on a stock motor with a lid, cat back, ls1 edit, cutout and under drive pulley.

I just called pace performance parts and they have them in stock for a great price but I need springs, retainers and keepers to go with them are ti. retainers needed?

I am only planning two more motor mods this winter one is the rockers and the other is a Meizer EWP so the rockers are the biggest and must have max gains. I will dyno after the rockers and before the EWP (I don't expect much of a gain with the water pump but it will help at the track) my last dyno was this past Sat so there will be a definite sign of the rockers on the dyno.

Anxiously awaiting your reply
Tony P.

 

Hi Tony,

Sorry for the delay in getting back to you, but I've been on the road! I have never seen any quality aftermarket rockers cause valve float by themselves. Valve float is a result of one or more of the following: inadequate seat pressure for the RPM and valve weight; harmonic issues with the spring at a given RPM: compatibility of the lobe profile to a given spring's harmonic characteristics (just because a spring works well on one cam lobe doesn't mean it's right for another-there is a lot of free performance to be found just playing with different springs on a given lobe); pushrods that are too weak for a lift profile and cause flexing; too stiff of a spring that causes the pushrod to flex too much; exceeding the dynamic stability range of the cam lobe,; etc. There are a lot of things that cause valve float, but the only rocker characteristic that really has any affect is that a higher ratio rocker will usually make a bad harmonic point worse!

Crane does not offer "beehive" design valve springs for pushrod engine applications. Much has been written about all of the theoretical benefits of "beehives", and I agree with most all of it when applied to OHC engines; but I don't agree with much of the theory as applied to "pushrod" engines. Our tests have shown several deficiencies in "pushrod" architecture engines because the harmonics of the pushrod seriously aggravate the harmonics of the "beehive". The relatively stable OHC architecture allows the "beehives" to work properly. We have seen that many beehives tend to cause false KR and we attribute that to "coil clash" of the top, closely wound coils causing a metalic "noise" that is picked up by the knock sensor. In addition, pushrod harmonics tend to "beat up" the valve spring. We like the "redundancy" of a dual spring design in the event of a spring failure. We have found that our 144832 spring has a harmonic signiture that is very compatible with a large number of popular aftermarket LS1 cam profiles. It works quite well with stock weight valves and actually provides a very symetrical "lofting" profile of stock valves in the 4800 to 6800RPM range with many of our lobes.

With respect to your efforts to get into the 11's on a cam only basis, I don't think the rocker or even the rocker/spring change will get you into the 11's by themselves. I hate to quote specific rwhp figures as they can vary so widely from dyno to dyno and atmospheric correction factors are not as good as most people believe. As far as titanium retainers go; our tests have shown that they only increase top RPM on the LS1's by about 200RPM. The dynamic stability of the lobe profile has a much greater affect on RPM. Two seemingly identical 224* profiles can have much different dynamic stability issues and actually require two different spring rates for compatibility! I think if you really want to go fast you need to change the cam. Take a look at the "Street-Shark" on our website www.cranecams.com. That car is driven 45 miles each way to work everyday. It gets 23.5mpg and it makes 400rwhp. The best part is the cam is only a 216/224 cam with our 1.8 "Quick-Lift" rockers. Hope this info helps! Mark Campbell