Could someone give me a rundown of the advantages/disadvantages of a hydraulic roller vs mechanical? Car is a fun driver and sometime racer, not my primary mode of transport.

THanks,
Doug

 

It's really a question of RPM

H-roller sub 6200 rpm

S-roller your rpm is only limited by your budget.

 

Thats it? What about durability, adjusting etc? I am considering a cam change and have been told that at least 20HP is being lost by not going solid roller.

Thanks,
Doug

 

Modern roller rockers usually keep their adjustment for a LONG time. No need to adjust them every weekend like the old GM rocker nuts. Personally I prefer the solid (flat tappet or roller) any day of the week over the hydraulic. That's not to say the hydraulics can't make great power. Just spend the $$ and get a high quality lifter.

What size are you thinking of going, out of curiosity?

 

Too much junk to brake and maintain with a solid lifter roller camshaft. A solid flat tappet is much more reliable on street driven pieces and will give you all the HP you will need.

 

The advantage of the mechanical roller is that the valve can be opened at a quicker rate, giving you more "area under the curve", or, more effective duration for the same advertised duration. More area under the curve means more air, or potentially better cylinder fill, thus more power. The ramp rate is limited on hydraulics by the "hydraulic intensity" of the lifter. In other words, if you try to move the lifter too quickly, the plunger could collapse or sink during the opening of the valve.

The disadvantage to the mechnical roller is that higher spring rates are required because of the faster lifter/valve action. The higher spring rates are harder on the rest of the valve train, especially the lifters and valve stems and guides. Racing cams are not recommended for the street because of the longer times street engines spend idling or running at low speeds. This is hard on the roller lifter because the roller will overheat because of the high spring pressure. At higher engine speeds there is more oil splashed on the cam and lifters which helps cool the roller. Lifter manufacturers have begun doing things like putting grooves in the lifter body to channel oil to the roller to cool it (cool being a relative term here).

There are mechanical rollers designed for street use though that still have the advantage of faster ramp rates over hydraulics (but not as fast a ramp rate as a racing lobe), and therefore don't require as much spring pressure as a racing cam.

I'm running a Comp Cams Extreme Energy street solid roller with the recommended springs (~150 lbs seat pressure). I've got about 15,000 miles my setup, and the valve train holds adjustment very well. I run through them every time I change the oil (~3000 miles) and have to tweak a couple, and that's about it.

Hope that helps,
Dan

 

Is there a difference in the durability of the two? And thanks for all the input!

 

If your a cruiser, stay away from roller camshafts. If your a racer and know what your doing, put it in. Personally I like a solid lifter flat tappet cam for the street. But as others suggested they get away with them. I dont like to work on anything but race cars, my Vette is sometimes used to tow them but it also never breaks down.

 

The nod for durability and reliability has to go to the hydraulic roller because the lighter spring pressure is easier on parts, and especially so if it's a factory roller block because the retro-fit roller hyd. lifters (and all mechanical rollers) use a tie bar to keep them in alignment, and those things have been know to break - it's another moving part. You can make very good power with the hydraulic roller. And, they're zero maintenance, which is attractive.

 

Danno:

Good post on the benefits/tradeoffs of mechanical vs hydraulic rollers. Whose lifters do you use with your cam?

 

I'm running the Comp Cams Endure-X lifters (#888) and 977 springs w/steel retainers. I don't know what the life expectancy is, but I'm not expecting GM factory type longevity. I'll be happy to get 40k miles out of them. I drive the car to work quite a bit. I've got about 60 passes on them at the drag strip, and last Spring I drove round trip from Austin, TX to Indianapolis, IN.

 

I'm not convinced that this statement is true. If the h & s-roller are of equal .050 duration and lift values the minimal change in ramp speed would have very few HP changes. I'm also talking the Extreeme ramp designs that are right on the edge.

A mild s-roller with good oil pressure and correct springs might last 50K + miles in a sub 7000 rpm motor.

The use of stud girdles and allen locking rocker nuts makes adjustment more of a check

 

I am looking at a sub 7K rpm motor. I am figuring to peak at around 6K, that would put me at the edge of Hydraulic lifter usefulness/reliability from my meager understanding of these things.

 

Modern day HR valvetrain parts (lifters) are usually good to 6200 and in some cases more before the real benefit of not having a plunger(SR) in the lifter takes effect. I'm guessing you are using a knock sensor? I'd go HR in your case. Just my .02

 

Go for the roller! I've got a solid, but with the new hydralic rollers, add the Rhodes slotted hydralic lifters, you have a really great street system. Might do that in the future. Why is GM using hydralic rollers now if they are not OK for street driving? Yes the lifts are a bit less, so the ramp thing isn't as important, but hey, unless you are doing killer drag racing, you can give up a couple of HP and still be VERY happy on the street.

 

Thank all of you for the enlightening input! Learned alot! Guess I will stick with the hydraulic rollers. Where can I find the Rhodes ones?

Thanks,
Doug

 

Doug, I will probably use hydraulic rollers too the next time I make a change. You should find someone that's used the Rhodes lifters and talk to them and really give that whole thing some thought. I tried some Rhodes flat tappet hydraulics one time and they made alot more noise at idle than my current mechanical roller setup does. I didn't like the noise at all, but some people like it alot. That's my input.

Dan

 

Wondering if the rhoads would set off the knock sensor.

Isn't there a less sensitive knock sensor/ I thought some guys use the Z06 one. I'd like to hear more about this

Good thread, btw! !

 

From Rhoads Site:

"You can actually hear Rhoads Lifters work! They have a sound all their own; a “mild ticking” sound at idle which tells you they're working"

"our competitor's ads that imply Rhoads Lifters are in some way unsafe for your engine because they tick"

"Rhoads Lifters are totally compatible with all hydraulic cams including today's modern state-of-the-are fast acting computer profiles. Performance cams benefit the most, but you can boost low-end torque by up to 15 hp with a stock 350 Chevy cam! Note: Rhoads Roller Lifters will be available soon. Check this website for further information."

I agree with the idea that a flat tappet will give more area under the curve, but I also think I like the idea of a roller as opposed to metal on metal like a flat tappet. Correct me if I am wrong here, but won't there be wear issues with a flat tappet as opposed to a roller lifter?
If the lifter noise is audible though, that could very well set off a knock sensor I think, and that would not be very cool. Is there a way to damp or filter the ticking? Does the knock sensor output a true DC voltage, or is it AC? Not sure what the frequency of "ticking" is as opposed to knock, but a notch filter on the knock circuit may work if the output is a reactive one, and as long as you are well above the half power point in the pass freqs, probably require a very sharp rolloff too though.

So in terms of efficiency and durability the hydraulic roller wins out. Seems to also be the best bet for a driver/street warrior. I know this, if I keep my Superram on, solid rollers are out as I have to pull the whole friggin intake to get the valve covers off.
The solid roller for all out performance/high rpms?

Man, You guys are awesome, I learn so much on here and I appreciate all of you sharing your knowledge so freely!!!



Doug

 

I don't have to pull the superram intake to adjust my solid roller. I do have to remove the AC compressor, but it's not that bad. I went with a solid roller mainly because I had an extra set of lifters and I like the sound of a solid lifter motor.

I think you can have a little more vacuum, a slighly better idle and can get a bit more duration at .050 for the same overlap as a hydro with a street solid roller. The drawback is extra maintenance and maybe a bit less longevity. It's all about what you like.

Rhoads lifers are another personal preference thing. I've used them in the past and wouldn't use them again.