Because it is a known fact and it gives them the distinct solid roller valvetrain sound that some people hate. Guys have used the Viper lifters in the Magnum V8s and V10s for years since the JTEC computer was speed density and nearly un-tuneable for years.

 

Kicking around the idea of trying Rhoads lifters in a 404 LS2 stroker with a 239/244 .62x/.62x cam.
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According to internet information under ~3,000 or so rpm should act roughly like a 229/234 .60x/.60x sized cam. Hopefully save a little gas and have great manners at lower rpm.

I wonder if Rhoads complicate tuning with the duration varying?


I think the sewing machine/solid lifter cam noises that Rhoads lifters make tend to get on a lot of people's nerves after a while and probably helped lead to the snake oil perception. Have read many accounts on other forums of many hot rodders trying them and pulling them out within three months or so due to the noise.

 

So, by effectively reducing duration, they fool the ECM into thinking it is a much milder cam at lower speeds, so idle can be more consistent

 

I had them in the GTO I purchased as the previous owner was using them to pass smog in that other country California. Had a very small cam for a 402 (224/232), but I can confirm on my very brief driving it (like 50 miles) anything below the pump-up RPM they took the LS sewing machine noise up a click.

 

The lift of the cam is literally lower than the grind at low RPMs. The plunger does not raise to its full height so part of the lift and duration are not sent to the push rod.

I used them years ago in a 3800 SC Fiero. The effect was quite obvious when I used Shell Rotella 5-40 oil.

 

Interesting! Playing with different viscosities (within the needs of the engine, of course) to vary the effectiveness of "controlled leakage" of the lifters.
Thinner oil, later "full pumpitude".
Thicker oil, earlier maximum lift and duration.

 

Pure speculation - on a possible Rhoads benefit:

Reducing lift by ~ .020 (or whatever it works out to be) could help reduce the amount of side loading on the valve stems from the stock rocker scrubbing with a higher lift cam in the under 3,000 rpm range.

Run a .645 lift cam and under 3,000 rpm it would provide ~.020 less lift so more like a .625 lift for low rpm.

Any thoughts on that?

 

You’re a genius. 🙂

 

Rhodes lifters have a patented groove down the side that makes them leak under pressure. As soon as the cam lobe comes up and starts to push the lifter against the pushrod, it starts to leak, and effectively loses a little volume of oil for the duration of the lift and allows the valve to close a bit sooner at the end. At low RPM and oil pressure this should be fairly considerable amount of leak-down which gives less lift, duration, and effectively advances the cam (all good things for low-rpm torque) at high RPM and oil pressure it should be less so and behave much more like a standard hydraulic lifter, but that isn't usually the WHOLE case.

This being a mechanical and uncontrolled hydraulic event, it varies based on many things, engine oil temperature is a big one, another is oil viscosity, clearance around the lifters, all that. It also introduces thinly controlled lash into the system along with the characteristic ticking and clatter like a solid lifter. Oil pressure is not perfectly dependent on RPM, even at stable temperatures, and even if you had stable pressure of 50psi, if you raise your oil temperature you will reduce viscosity. You will probably want to consider running more oil pump because you have 16 leaking lifters. Leaked down lifters do not set the valve down smoothly, but with an aggressive close as the lifter is still on the "high speed" section of the lobe when the valve hits the seat.

Another thing to consider is you never get all of your cam, it's impossible to get full duration and lift using these funny lifters.

Another potentially bigger issue would be how this could mess with your EFI system. Could you tune an EFI that had 20 degrees of uncontrolled cam duration between hot and cold oil temperatures and high and low oil pressures? Go from a 0 overlap cam to 20 degrees? Rhoads lifter seem to me like you installed 16 gremlins into your engine. With a carburetor you could make it seem like it was working but even then I would probably use something more reliable, like a standard hydraulic roller lifter.

I think there is good reason why all of the OE manufacturers who do have some variability on their cams use reliable, positive mechanical controls instead of something like a rhoads lifter.

 

Yeah, it would seem there are too many variables in play here. It has to drive an ECM nuts.
One thing I was wondering about was the bleed groove, and whether there is anything to be gained (or lost!) by varying the length and/or placement of the groove. I'm sure Rhoads has experimented the life out of them, but i was curious about these aspects.

 

Marland Davis Rhoads Lifters Dyno Test by TPIS (LS1) & Gale Banks (Big Block 454)


Tried calling Rhoads after reading article to ask for a clarification on proper lash for:

1) aluminum block & aluminum head LS
2) iron block aluminum head SBC/LT/LS
3) iron block and heads.

Rhoads is out of the office until Nov 7th per prerecorded message.


Take away in my humble opinion from article is for an aluminum block LS, get ready to fiddle and test experimenting with the lifter preload aka defacto valve lash. Rhoad's per article is .035 for a cast iron block & heads. The LS1 in article article lost 35 hp off the top set at .035 cold because hot valve lash was closer to .048 as block and heads expand. They tighten preload/lash during dyno test and netted improvement but didn't get it dialed in exactly so we didn't get a spec.

Doing the tuning and dyno time necessary to "hot lash" and determine the best set up for the Rhoad's lifters on an aluminum block & heads sounds like a costly hassle to me.

I may call back in a few weeks and see if Rhoads has any additional information to share. Definitely makes the stock LS7 lifter, Morel lifters & Johnson lifters look more appealing than ever IMO.

 

Does not mess with my PCM at all. Just tune the VE and Spark table. Just have to watch the 1/2 point of so of dynamic compression the reduced lifter action increases ths DCR.

 

If this was as reliable and effective of a magic bullet as some articles claim, every engine would use them.

 

As I have mentioned before ALL OBD2 Viper engines used them. My idle vacuum is high at 19 in/hg @ 725 rpm, low speed torque is awesome and I cannot complain at all about 20 mpg highway in a box rolling along at ~7,500 lbs.

0.035" is double what Rhoads recomeends for street use with the V-Max lifteds. They suggest 0.020" hot. Since I do not have a way to do hot adjustments, with a cast iron block and aluminum heads, mine are cold lashed with 0.014". I am definately not losing a ton of top-end power from them. My power peaks at 5,600 rpm with a 218/228@ 0.050 on a 108 LSA cam and the power curve hangs on until 6,200. They do generate a bit of noise but not too much more than the crummy GM LS7 lifters. I have had 2 sets of LS7s go bad in 20K miles combined. One set developed two bad rollers. The other set had one that collapsed. The last set of lifters I used came out of a Vortec 5.0L with 120K on them. I dissasembled each one, keeping the parts together and cleaned them in my heated ultrasonic cleaner, then re-assembled them with snap rings rather than those stupid spring clips. 50K later the engine is still running great.

 

What would you use for aluminum block & aluminum heads?

 

A Morel 7717 hydraulic roller lifter.

 

agreed.....but just for fun and games with the Rhoads what lash should one use aluminum block & heads ?

 

For a V-Max lifter in an aluminum block and head engine, it would be 0.008" feeler gauge and then plunger fully bottomed out for initial startup. Then you could recheck it hot for 0.020" from bottomed out. V-Max lifters are lashed from distance off full travel. If you want to minimize their effect, use 0.040 off the bottom.

 

I was reading a new article in LSXmag.com on lifters

Howards Cams Educates Us on LS Lifters

Handy link to article on LSXmag.com

"Those concerned with GM’s lifters can purchase an LS7-style lifter from an aftermarket company. Howards Cams sells a drop-in lifter good for 8,000 rpm, made by Morel, that uses the plastic lifter tray and is very easy to replace. Luke says these aftermarket lifters come in three different variations, all of which are hydraulic: OE performance, variable duration, and max effort. The OE performance is self-explaining, as they work like the stock LS7 lifter. The variable duration lifter is a fast bleed lifter, “which is a little excessive for a street car,” said Luke. “This lifter will bleed 10 degrees of duration at idle, which calms the car down, provides vacuum, and makes the car driveable. When the oil pressure spikes with RPM, the lifters pump up, allowing a big cam’s peak performance. For a guy who wants a 2,000 rpm stall converter, they can use variable duration lifters and drive on them daily.”"

I was not able to discern from the article what lifter they were talking about but I found these on the Howards website: OE STYLE VARIABLE DURATION HYDRAULIC ROLLER CHEVY 305-350 / GEN III (LS-SERIES) LIFTER SET; HOWARDS CAMS 91113FB