Rhoads Vari-duration lifters?

[WZ JUNK]

Has anyone had a problem with Rhoads Vari-duration lifters causing a miss at low RPM?  I am helping a friend chase a low RPM miss in his engine.  The miss is on one particular cylinder and we have ruled out electrical problems.

[Dave]

Has anyone had a problem with Rhoads Vari-duration lifters causing a miss at low RPM?  I am helping a friend chase a low RPM miss in his engine.  The miss is on one particular cylinder and we have ruled out electrical problems.

If i remember right from years ago that was a common problem with them.
The way to cure it gm stock lifters  
Dave

[Sean]

All I remember about them is the clicking noise they made. I knew one guy that tried them back in the 80's.  Nobody else around here would buy them after hearing them in his car. They seemed to run allright though.

[Bob Paulin]

My initial experience with the Rhoads lifters was when they were first introduced as a "cheater cover-up."

They were originally marketed as a way of "softening" a high-lift (illegal) camshaft's "rump-rump" in order to not draw attention to the race car. (Yep! We tried 'em!!!)

Unfortunately, their variable duration works pretty much backwards - advancing the cam timing as revolutions increase, and the lifter pumps up - to be of much performance value......

.....that coupled with the aforementioned quality issues would be enough for me to walk away from them.

I actually had one so-called "engine builder" try to tell me that they would actually lift MORE than the camshaft's actual specification when they pumped up, but he couldn't explain how the valve would seat if the lifter was holding it open further.

Anybody here ever experience a faulty, pumped-up hydraulic lifter???

After I first ran across them - I believe it was in the late '60s - they were marketed to people who were actually trying to build streetable race cars.....big cam, but streetable at low RPMs.

Didn't really work well then, either - as mentioned above, often mimicking the sound of a Ford Y-block in need of a top-oiler setup - and I haven't really seen any technological breakthrough, so I'll maintain my position on them.

They are, essentially, hydraulic lifters with an attempt at controlled leakage/lifter collapse to reduce camshaft lift at lower RPM.

B.P.

[slocrow]

They were originally marketed as a way of "softening" a high-lift (illegal) camshaft's "rump-rump"

Unfortunately, their variable duration works pretty much backwards -

Anybody here ever experience a faulty, pumped-up hydraulic lifter???

Interesting Bob. I never heard of them, probably because [as you said] they didn't work.
Splain sumtin to me please. How were they supposed to work? I thought the "rump-rump" is caused by duration (over lap), not lift. If correct, how were these supposed to vary the duration.
I remember backing off the hyd lifters so they would be in a constant state of pump-up, supposedly to avoid lifter pump-up and allow the engine to rev all the way to valve float but of course this didn't change the duration.
This kind of reminds me of that fictitious Yak-a-meme (sp) camshaft in the "if it don't go, chrome it" era. Their catch phrase was "the faster you go, the higher the lift".
Thanks, Frank

[1FATGMC]

Interesting Bob. I never heard of them, probably because [as you said] they didn't work.
Splain sumtin to me please. How were they supposed to work? I thought the "rump-rump" is caused by duration (over lap), not lift. If correct, how were these supposed to vary the duration.

Since they are partially collapsed at lower rpms the cam has to turn further before it starts to lift them, so the duration that the valve would be open would be less.

Summit still sells them for $99.95 a set not that I would spend my money on them.

c ya, Sum

[rumrumm]

In theory, they are a great idea. But there are two problems associated with them: 1) they are hard on the valve train; 2) they may not pump up 100 per cent so you are not getting the full benefit of your cam. Crane has a variable duration lifter similar to Rhodes that does not give you the ticking noise.

[Bob Paulin]

Interesting Bob. I never heard of them, probably because [as you said] they didn't work.
Splain sumtin to me please. How were they supposed to work? I thought the "rump-rump" is caused by duration (over lap), not lift. If correct, how were these supposed to vary the duration.

Since they are partially collapsed at lower rpms the cam has to turn further before it starts to lift them, so the duration that the valve would be open would be less.

Summit still sells them for $99.95 a set not that I would spend my money on them.

c ya, Sum

Sum hit it dead square.....

B.P.