variable duration lifters
08-18-2005, 04:04 PM
#2
Rhoads variable duration lifters are a little noisy much like a solid lifter cam until oil pressure and RPM's goes up. But they do work good at improving a big cams idle and drivability. Ken Crocy? of HO Racing is a big believer of these lifters.
08-19-2005, 07:24 AM
#5
Originally Posted by 02sierraz71_5.3
are they actually able to increase low end
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08-19-2005, 08:30 AM
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These look very intersting...It says that they must be used with and adjustabel valvetrain. Does that mean I would have to buy adjustable RR's as well? I'm sure this would really help tame a G5x3-4 and TRex type cams, and give them much better street maners.
08-19-2005, 12:38 PM
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Actually they are $205 from Summit...You are looking at the wrong ones.
http://store.summitracing.com/defaul...=egnsearch.asp
Correct part number for app: RHL-RL1728
I just want to know if anyone here has used them, and if I can use my stock rockers?
http://store.summitracing.com/defaul...=egnsearch.asp
Correct part number for app: RHL-RL1728
I just want to know if anyone here has used them, and if I can use my stock rockers?
08-19-2005, 04:49 PM
#12
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hot rod did a recent test with these lifters for the LS1 and they didn't run into any knock retard problems, so the knock sensor won't retard the timing. They used the variable adjust rockers for the test. I called up roads and they said they make a none adjustable type for the stock valvtrain which is still 200 bucks. I'd love to use these, but having to take off the heads to put them in doesn't appeal to me. I've used them on older cars and they do work very well, a little noisy as mentioned but the pros outway the cons. They told me it not only gives better idle and vaccum, but also makes the cam much smaller, by around 10 degrees duration, so for guys living in emission staes like California can benift from these lifters, since they can run a bigger cam and have lower emissions. So instead of having a 224/224 114 cam pass you could run a 234/234 cam-at least this is whta they tell me, I'd like to see some proof, and wonder why more people don't use these in emission states to get more cam. I would definetely put in a pair if I were to get some ported heads
08-19-2005, 06:37 PM
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Just got some answers from rhoads in an email:
"Our original Rhoads Lifters do not require an adjustable valve train, however, our new VMax Rhoads Lifters which give greater or lesser leak down control does require an adjustable valve train. Rhoads Lifters can be used with smaller performance cams as well as larger ones."
Im definately gonna use these on my next build I can run a bigger cam, have better streetability and I would think you could get away with alot less stall on top of it.
Imagine running a tr 224 in a 5.3 with the stock stall and having power from 1000 rpms this is great. I wish I had known about these sooner for 200 bucks they seem like a very worthwhile mod
"Our original Rhoads Lifters do not require an adjustable valve train, however, our new VMax Rhoads Lifters which give greater or lesser leak down control does require an adjustable valve train. Rhoads Lifters can be used with smaller performance cams as well as larger ones."
Im definately gonna use these on my next build I can run a bigger cam, have better streetability and I would think you could get away with alot less stall on top of it.
Imagine running a tr 224 in a 5.3 with the stock stall and having power from 1000 rpms this is great. I wish I had known about these sooner for 200 bucks they seem like a very worthwhile mod
08-19-2005, 08:42 PM
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I've used Rhoads flat tappets before. They do work as advertised. However, you'll notice the advertisement doesn't talk much about the mid range. What I found was that the mid range was compromised & felt a little flat until the lifters pumped up fully at higher rpms. I tried adjusting preload & changing to different weight oils to get the net effect that I wanted. Changing oil weights did have a noticeable affect on the lifters. It was kind of fun experimenting with those lifters. Anyway, if you only care about top-end power then these lifters may be worth it. If you care about the whole rpm range, then be forewarned about the soft midrange. HTH
08-19-2005, 08:47 PM
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Originally Posted by nuzee
I've used Rhoads flat tappets before. They do work as advertised. However, you'll notice the advertisement doesn't talk much about the mid range. What I found was that the mid range was compromised & felt a little flat until the lifters pumped up fully at higher rpms. I tried adjusting preload & changing to different weight oils to get the net effect that I wanted. Changing oil weights did have a noticeable affect on the lifters. It was kind of fun experimenting with those lifters. Anyway, if you only care about top-end power then these lifters may be worth it. If you care about the whole rpm range, then be forewarned about the soft midrange. HTH
08-20-2005, 01:19 AM
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I track tested going from a 10-30w to 20-50w oil. Changed the oil right at the track. I gained a solid tenth & 1 mph, IIRC, could have been slightly more like 1.5 sec & mph. Running around with the 20-50w caused my rocker arms to squeek so I eventually ran very little preload and went back to a lighter weight oil. Running less preload reduced the effect of the lifters. Switching back to conventional lifters gained another tenth IIRC. This was awhile back so I can't remember all of the details.
I originally used the rhoads to help a low compression motor cope with a moderate cam. It did help build up torque in the lowend and made driveability better. I then corrected the low compression with better heads and continued to use the rhoads. Lowend was pretty snappy but the mid range was just not as explosive as it should have been for that sized cam.
If you use it with an over-sized, high-lift cam, maybe the results would be different. But with the aggressive roller cam lobes available which create a nice wide powerband, I don't see as great a benefit using Rhoads lifters as it was for old school flat tappet motors.
I originally used the rhoads to help a low compression motor cope with a moderate cam. It did help build up torque in the lowend and made driveability better. I then corrected the low compression with better heads and continued to use the rhoads. Lowend was pretty snappy but the mid range was just not as explosive as it should have been for that sized cam.
If you use it with an over-sized, high-lift cam, maybe the results would be different. But with the aggressive roller cam lobes available which create a nice wide powerband, I don't see as great a benefit using Rhoads lifters as it was for old school flat tappet motors.
08-21-2005, 10:38 PM
#20
Rhoads lifters I've been running them since 2004. One of their earlier customers for an LS application. I believe they are based on stock gm hydraulic lifters that are disassembled and modified (as I understand it from discussing them with the company owner)
My combination is an Eagle 383 stroker with stock rockers, hardened pushrods, custom roadracing grind cam by EDC that makes power through 7K+., Wiseco forged offset wristpin pistons with reliefs, C.R. of ~12:1, PP Stg 2 hand ported 5.3 heads (2.02's) milled 25K, Cometic gaskets, longtubes, dual 3" with Dr. Gas x-pipe, Random Tech cats and Borla XR's, LS6 intake 42 lb injectors, Ported tb, stock maf, fluidamper pulley, aluminum flywheel
-fully balanced and blueprinted rotating assembly
Dynoing this week, will post curves for your opinions.
The car is not fully tuned yet, but will idle dead steady at 850 RPM with these lifters. Full throttle mixture is OK but the mixture is somewhat rich in most other places. Seems to pull hard to 7K+
Been driving with these lifters for sometime and am really happy with how well the engine performs at low rpm. Haven't used other lifters, so I can't make any direct comparisons, so I'll let the graph curves speak for themselves.
T
My combination is an Eagle 383 stroker with stock rockers, hardened pushrods, custom roadracing grind cam by EDC that makes power through 7K+., Wiseco forged offset wristpin pistons with reliefs, C.R. of ~12:1, PP Stg 2 hand ported 5.3 heads (2.02's) milled 25K, Cometic gaskets, longtubes, dual 3" with Dr. Gas x-pipe, Random Tech cats and Borla XR's, LS6 intake 42 lb injectors, Ported tb, stock maf, fluidamper pulley, aluminum flywheel
-fully balanced and blueprinted rotating assembly
Dynoing this week, will post curves for your opinions.
The car is not fully tuned yet, but will idle dead steady at 850 RPM with these lifters. Full throttle mixture is OK but the mixture is somewhat rich in most other places. Seems to pull hard to 7K+
Been driving with these lifters for sometime and am really happy with how well the engine performs at low rpm. Haven't used other lifters, so I can't make any direct comparisons, so I'll let the graph curves speak for themselves.
T