bletour2001

Is anyone running this combination? I have a set of Crane "Accelerated Lift" rockers (1.7s but they start lift as 1.79s) and was thinking of putting in an XE-R lobed cam. I have read that you shouldn't use 1.8 rockers with the XE-R lobes due to the fast ramp rate already present in the lobes. Is that strictly to save the springs or P/V clearance issues? I have Patriot Gold Duals on the heads so the valve springs are good. Anyone?

--Bill

PREDATOR-Z

Judjing by the year of your C5 (01), I would just use the stock rockers.

bletour2001

Well I could put them back on...but I'm not a fan of their bearing throwing ways....I would rather be safe than sorry.

--Bill

GTS346

iTrader: (1)

I dont think 1.8 rockers would go good with XE-R cams as they already have high lift.
What size XE-R cam is it, as 222-226 are around 0.581-0.585" lift with 1.7's so you'd be around 0.611"-0.616" with 1.79 ratio.

Or do these rockers start at 1.79:1 and at max lift there only 1.7:1?
How do they adjust?

mrr23

iTrader: (3)

what they do is start at 1.79. then at about .250 lift, they convert back to about 1.72. so, your overall lift won't increase by much. it's all about opening and closing the valve as quickly as possible without beating up the valves and seats. i put the 1.89 accelerated lift on my 99 formula with stock cam. gained a solid 10/10 with them. http://www.vincihighperformance.com/...RTSPARENT.HTML

Joe Vinci

iTrader: (3)

We have profiled the XE-R cams and although they have a faster ramp than some cams, the VHP/Crane quick lift profiles are more aggressive. We use the quick lift rockers to enhance the performance of all our cams and have received gains in both horsepower and torque from them with no ill effects. The rockers are provided in two different ratios to support the large variety of camshafts. Don't forget about the stronger push rods, guide plates and screw in studs that come with our kits. The increased strength of the valve train is often overlooked. Roger

PREDATOR-Z

Look at what cams the Crane rockers were designed for (Crane Cams).
Look at the lifts on these cams. Nothing like the higher lifts of an XE-R.
IMO not wise to use them together.

Mark Campbell

At Crane R&D we constantly evaluate our competitors lobes, rockers, valve springs, etc. I'm sure they constantly check ours as well. We test lobes with various combinations of rocker arm types, rocker ratios, valve springs, installed seat pressures, various spring rates, etc. We do it all day, every day because that is our passion. In addition, we work with many outside specialists such as Vinci High Performance in Orlando. With all that said. I can state with 99.99% certainty that our "Quick-Lift" rocker arms will only enhance the performance of any LS1family cam you have. They will not, in any way, lead to damage of other components. Our "Quick-Lift" geometry is based on the location of the pushrod seat with respect to the valve tip and the center of rocker rotation. A 1.7 (advertised) rocker starts the valve off the seat at a ratio of 1.79 and due to the motion of the pushrod seat the rocker ratio changes to 1.72 by .250-.300 net valve lift (depending on profile design). At approx. .250 valve closing the ratio returns from 1.72 to 1.79by the time it reaches the valve seat. This designed rocker body geometry provides an additional 4-6*of duration in the .200"-.300" net valve lift area. This means the valve is getting open faster and closing later on any lobe. This provides more effective duration with the same seat-to-seat timing. What we are trying to do here is get as close as possible to the opening and closing rates available to OHC engine designs. If you are not convinced that we have done our homework on these rockers, install a degree wheel on the engine and plot lift per degree of rotaion with our rockers vs competitors rockers. In addition, put some machinist blue on the tip of your valve stem and adjust your rockers and turn the engine through a couple of revolutions. Remove a rocker and check the nose wheel sweep area in the blueing on the tip of the valve. Then do the same thing with a Crane "Quick-Lift" rocker. You will find that the nose wheel sweep on our rockers is considerabley less than any of our competitors. This reduces valve stem sideloading and valve guide wear (friction). It also results in slightly more valve lift. Again, the use of Crane "Quick-Lift" roller rockers (part # 144750-16, 1.7 advertised ratio; 144759-16, 1.8 advertised ratio) will only enhance valve action of any lobe with which they are used!

71CamaroLS1

Tony Mamo uses these rockers on his AFR-headed car, and recommends them. The AFR cam is a custom grind on XE-R lobes.

bletour2001

Thanks Mark! Love to hear from the R&D guys themselves! So I do have another question about your "Accelerated Lift" cams as well. Are these similar in design in that they start the lift off rapidly and then ease off at .200+? When used in combination with your rockers you would get almost a doubling of the effect?

Thanks,

--Bill

jz06man

I guess I'm call ing Vinvi and order a set of 1.79 rockers.

Thanks Mark

PREDATOR-Z

Mark, thank you for opening my eyes on these rockers.
Would it be possible to have a table those rockers effect on lifts from .100> .600???
On an XE-R that you have tested.
And also do they fit under stock valve covers (All LSx motors) without any modifications or spacers?

jz06man

Mark,
Can you post the same table for a crane cam.

Mark Campbell

The rate at which a cam designer opens a valve depends on a lot of factors. One of the most important is the impulse induced in the valve spring by the initial movement of the lifter from the basecircle to the lobe. Hydraulic rollers do not use clearance ramps like solid rollers and depend on a slight movement of the hydraulic plunger in the lifter body to cushion the initial impulse. Spring seat pressure, oil viscosity and temperature, oil pressure, etc. all affect this to some degree. (Contrary to some posts on threads here, shimming valve springs only affects the seat pressure and spring pressures at associated lifts. Shimming a spring has NO affect on spring harmonics and will not prevent a broken spring as it does not change any of the physical characteristics that affect the harmonics). Our 144832 spring was designed to allow the use of lobes with very quick initial opening rates without tickling any critical harmonics of our new spring. We have designed our lobes to take maximum advantage of the 832 spring. Spring harmonic characteristics and their relationship to the design factors of the lobe are the second leading cause of spring breakage. The first cause of spring breakage is just undetected flaws in the spring wire caused either in manufacturing, shipping or handling!

Spring harmonics are directly related to physical spring characteristics such as free length, wire diameter, O.D., number of active coils, etc. Material has no affect on harmonics but does affect spring life and load loss. The lift table of a lobe (rate of opening and closing)as well as rocker arm ratio, and pushrod stiffness have critical influences on how harsh the harmonic reactions of the spring become. If a spring operates long enough at critical harmonic RPMs it will either lose load or fail. We design our lobes to provide the quickest opening commensurate with acceptible life. If you are breaking springs, you need to look at the compatibility of the spring with the lobe and the RPM range you are running in. There are so many permutations here that it most frequently accomplished by trial and error and nobody can know it all. Just because a spring works great on one lobe does not mean it will work great on others. We want to sell springs so we have designed our springs to be compatible with many competitors (but not by any means all) lobes. Our 144832 has a very flexible harmonic profile that is the direct result of its spring rate. We designed this spring with a moderate rate and lots of usable travel so that it could be installed at 112#@1.800" for use on trucks and SUV's and yet it could be shimmed to 130-135# and still be run with .625lift. Its first severe harmonic does not occur until over 7200RPM on most popular lobes. Seat pressure needs to be higher for higher engine speeds but you don't want the rate too high or you will have unwanted pushrod deflection at high lift which causes valve train instability.

With all of that said, the new spring has allowed us to be extremely aggressive in our new Quick-Lift lobes. Hope this helps. Mark

Mark Campbell

I'm sorry, but it is not Crane's policy to post design info in public. In addition, while we have many competitors, we respect their abilities and we have good relationships with most if not all of them. This is an odd industry with many companies started by racers who helped each other at the races. Other industries think it is odd, but many of these companies regularly deal with each other. We do business with many of our competitors(they buy parts and subassemblies from us and we buy from them)every month. I am not interested in starting a verbal confrontation on this website with people I consider friends or good acquaitances.

In response to a question on a related thread, our rockers will fit under all 1999 and newer LS1 family valve covers. There are a few 1997 and 1998 valve covers that require the slight grinding of one or two rockers per bank, but we have only heard of this on two or three occasions. We will be offering a shaft mount system in the next year. It will use our new "polymer matrix composite" bearings. Unfortunately, it will probably require a valve cover spacer like everyone else's. We have not put the LS1 engine family near the top of our list in shaft mount development because the valves of the LS1 are so light and the necessary spring pressures so modest that the advantages of a shaft mount on the LS1 are extremely difficult to find on most applications. Generally you need to be above 500# open pressure to see any advantages of a shaft mount. We have dynoed our "Quick-Lift" stud rockers on engines with open pressures of 400# and not seen any advantage to any competitors shaft systems. In fact, none has made any more horsepower and some made significantly less.

Squintz Palladoris

iTrader: (1)

I am running the 1.79s (1.7) on a G5X3 with Patriot duals. They work Great!

I also did a H/C combo for a Friend of mine and used the 1.89s(1.8) with one of Roger Vinci's Camshafts. This is an excellent combo as well!

Brad