http://hotrocker.com/tests.html

Interesting stuff. Wonder if the price is right....

 

I would just love to have it just so I can see some rice boys jaw drop when i tell him i have a vtec 383. LOL

 

Just wondering if anyone had any comments on this. Im surprised some of our, "major" techs here havn't commented on these.

Seems like a good idea... with these rockers, wouldn't you be able to run a much higher lift cam, and benefit more from buying heads with larger intake cc's without ruining the low end power?

 

You must not have been browsing the other posts on these. This started over a year ago, and the prevailing attitude (not necessarily a concensus) was that the durability was in question. Everyone wanted someone else to be the guinea pig....

The determination was made that a set of fast bleed lifters (like Rhodes lifters) accomplish the same thing to almost the same degree - shorter duration and less lift at low RPM, more duration and lift at higher RPM. They've been available for 30 years, and some people use them.

V-Tec (variable valve timing) isn't a new idea, by any means. It's just another one the Japanese "borrowed" and enhanced, in their typical fashion. There isn't a lot of true innovation in the east, just "copy and refine".

 

Vader, i browse these boards all of the time, and I don't rememeber ever hearing about these. That's why i posted about them.

Oh well, a speck under a grand is expensive for the kit, but I wonder if the gains would really be worth it. It's sold as a street kit, so it isn't some hardcore thing.

I notice a lot of people run the AFR hydro-kit or whatever, and from what I know, they kill lots of power up to 5K, then produce much more high end. Seems like this would be much better alternitive to their system.

 

i remember reading one of the car magazines about this.

i think it was hot rod or something, If i had the money i would try it, but that if is not now.

 

i saw the post on those things. I wouldnt want that in my engine. Just dont trust 'em. As for vtec, ive used a honda with it and it aint that great...

 

The AFR hydra-rev kit will absolutely not affect low end power. It has nothing to do with duration or lift, it just keeps the lifters on the cam.

If you want something variable, do what Vader mentioned.. go get a set of Rhoades lifters. I think they cost about $100-150 bucks for a set.

 

Ok, i learned more. Big reason why I posted about this.

Vader, madmax, everyone, thanks for the input!

 

Yup. Check this post from about nine months ago: https://www.thirdgen.org/techbb2/sho...threadid=32312

There have been more posts since then as well.

I have also done some more investigation since then. This may get a little long, so go get a beverage - I'll wait...

If you calculate the range of ratios offered by the VVT system (1.1:1 through 1.7:1), you'll discover that the lift difference at the valve is in the neighborhood of -26% to +13%. On a typical camshaft lobe of 0.450" lift and 200° duration, the VVT rockers could vary the maximum lift from 0.340" to 0.510" At the camshaft, that would be an effective difference of 0.120" lobe lift change.

Rhodes (fast bleed) lifters bleed down to nearly "empty" at low RPM, providing a 0.100" decrease in effective cam lobe lift. At high RPM, the lifters hydraulically "lock" almost immediately, providing full lift. In other words, a set of high bleed lifters and 1.6:1 rockers with the properly selected cam would provide essentially the same variation in valve lift, and provide a greater change in duration. Actually, the lifters shorten the duration even more effectively, since they operate directly at the cam rather than at the rocker. More of the lobe rotation is spent in compressing the lifter before the push rod is moved than the minuscule difference that is affected by a rocker ratio change. Study a cam graph and the rotation to reach the 0.100" lift point is far greater than the miniscule duration change caused by a rocker ratio variation. With the VVT rockers, the lifter would ride up the lobe at the same time in the cycle, making duration changes less apparent.

And for over $1,000 by the time the parts are shipped to you, you will spend more than a set of liftersm timing chain, camshaft, AND performance rockers. And then there is the installation and control issue. Once it's installed, the durability is still a big unknown.

 

We don't need no V-Tec. We have real cars.

 

where can I pick up a set of these Rhodes Lifters and do they come in roller form??

 

http://64.90.9.168/cranecams/pdf/214e.pdf

http://www.amotion.com/tech/rhoads.html

http://www.compcams.com/catalog/256.html

Crane does not offer them in a roller design. Both Rhodes and Crane have onlt 0.030" lift reduction at low RPM. The Comp specs were not readily apparent on their site or in their literature.

 

I would defenately like to hear how these work from someone else before I go spending $1000 on a set of rocker arms. This would vary lift way more than a set of fast bleed lifters. It would take my current cam from .33intake at 1:1 to .56 at 1:1.7. That is quite a differance, and the bigger the cam, the greater the differance. I would worry about the reliability on a high hp, high rpm engine. You would also have to make sure there is plenty of clearance between the valves and pistons.

 

92,

The lift would be varied more by altering the rocker ratio (or varying it). The duration will vary more with the high bleed lifters than with the variable rockers, however. And it's the duration that is going to have the greatest effect on idle quality with a HP cam profile.

If you study the dynamics of the valve train, you'll see that the "wasted" motion from compressing a lifter an additional 0.030" requires more rotation of the cam lobe than the variation of the rocker ratio.

The topic has been discussed (and argued) numerous times when the change from 1.5 to 1.6 rockers was in question. Changing the rocker ratio does make a minute change in duration, but with a high bleed lifter, the valve train essentially "ignores" the cam profile until the lobe has rotated enough to compress the lifter the extra .030" to lock it hydraulically.

With variable ratio rockers at the 1.1:1 position, the cam lobe would have to rotate a bit farther to operate the valve train to the 0.075" valve lift position. This is the lift point at which almost all camshafts are rated for duration (0.050" lobe lift, 0.075" valve lift) in advertised cam specifications. To be precise, the cam lobe would have to affect an additional 0.014" of lift with 1.1 rocker ratio. Compared to a fast bleed lifter, with which the cam has to rotate to affect an additional 0.030" before the valve train moves at all, then an additional number of degrees (depending on the cam profile) to reach the 0.075" valve lift point, the variable rockers have less than HALF the effective duration difference than a fast bleed lifter. Study the graph of the lobe profile of any cam, and change the duration lift points from 0.050" to 0.080" (adding .030" for the fast bleeds) and you'll discover that with even the most conservative cam grinds the duration of valve lift is reduced by 20°. This is usually enough to eliminate all overlap, or reduce it to the point of insignificance. Graph the same lobe with a 1.1:1 rocker and you'll realize that the duration change is a lot less affected.

Duration of valve events is going to have a far greater effect on low RPM engine performance than net lifts. So with the fast bleeds, you can select a cam profile that will provide the desired peak lifts, yet operate it at reduced duration and slightly reduced lifts for normal street use.

 

Thanks for the info vader. I wonder how the fast bleed lifters, and hotrockers would work together?