Variable CAM/ Valve Timing for SBCs: Why is this not a thing?
08-03-2016, 12:57 PM
#41
Melting Slicks
Thread Starter
Actually two of the most successful engines that addressed the idea of having more than one cam profile available were the Corvette ZR1 and the Taurus SHO. Their systems didn't rely on hydraulics as much as they did on their PCM to activate a second set of injectors and throttle plates to open a second set of intake ports. Both were unfortunately short lived, but both produced significant power increases while offering substantial fuel economy when desired.
I installed a set of Rhoads lifters on a SBF (302) I built for a Mustang in the 70's. The cam was hydraulic, but had a profile similar to the Ford 271 hp solid from the 60's. It pulled hard from about 3000 rpm to well past 6000 rpm. The engine idled at 800 rpm, had a nice lope to it and when driven normally, it got better than 18mpg even though it had 3:90 gears. Back then I considered it having my cake and eating it too... The lifters were just noisy enough that many thought it had solid lifters.
Good luck... GUSTO
I installed a set of Rhoads lifters on a SBF (302) I built for a Mustang in the 70's. The cam was hydraulic, but had a profile similar to the Ford 271 hp solid from the 60's. It pulled hard from about 3000 rpm to well past 6000 rpm. The engine idled at 800 rpm, had a nice lope to it and when driven normally, it got better than 18mpg even though it had 3:90 gears. Back then I considered it having my cake and eating it too... The lifters were just noisy enough that many thought it had solid lifters.
Good luck... GUSTO
Cool! Awesome real-life examples; thanks for sharing.
I'm really, REALLY torn on the Rhoads lifters; I haven't found anything where there's more sharply conflicting information and contradictory opinions so far. If they WORK they're exactly in alignment with what I want for my build.
-BUT why is there no externally confirmed proof? -If they work so well, they'd be touting the independent confirming dyno results that show the same cam with regular vs. Rhoads lifters and an improvement in torque on the low end and equivalent HP and RPM peaks on the high end.
I'd be particularly interested in their hydraulic roller lifters option, but again only assuming it actually works or they had some money back guarantee. I don't mind running a specific oil pump and specific weight oil to make them work, but if I do, I'm going to do a before and after dyno test with the same CAM and if they don't do what they purport to do, I'm going to want to send them back.
Again the lack of evidence despite them being out for DECADES isn't a good sign.
Adam
08-03-2016, 01:55 PM
#42
Le Mans Master
Cool! Awesome real-life examples; thanks for sharing.
I'm really, REALLY torn on the Rhoads lifters; I haven't found anything where there's more sharply conflicting information and contradictory opinions so far. If they WORK they're exactly in alignment with what I want for my build.
-BUT why is there no externally confirmed proof? -If they work so well, they'd be touting the independent confirming dyno results that show the same cam with regular vs. Rhoads lifters and an improvement in torque on the low end and equivalent HP and RPM peaks on the high end.
I'd be particularly interested in their hydraulic roller lifters option, but again only assuming it actually works or they had some money back guarantee. I don't mind running a specific oil pump and specific weight oil to make them work, but if I do, I'm going to do a before and after dyno test with the same CAM and if they don't do what they purport to do, I'm going to want to send them back.
Again the lack of evidence despite them being out for DECADES isn't a good sign.
Adam
I'm really, REALLY torn on the Rhoads lifters; I haven't found anything where there's more sharply conflicting information and contradictory opinions so far. If they WORK they're exactly in alignment with what I want for my build.
-BUT why is there no externally confirmed proof? -If they work so well, they'd be touting the independent confirming dyno results that show the same cam with regular vs. Rhoads lifters and an improvement in torque on the low end and equivalent HP and RPM peaks on the high end.
I'd be particularly interested in their hydraulic roller lifters option, but again only assuming it actually works or they had some money back guarantee. I don't mind running a specific oil pump and specific weight oil to make them work, but if I do, I'm going to do a before and after dyno test with the same CAM and if they don't do what they purport to do, I'm going to want to send them back.
Again the lack of evidence despite them being out for DECADES isn't a good sign.
Adam
First and foremost, they addressed one of the biggest limitations of using a hydraulic cam back then, the rpm limit at which any hydraulic lifter would float the valves (re: act as a rev limiter). The answer was to run "anti-pumpup" lifters to gain more rpm - and power, without having to use a solid lifter cam. Typical anti-pumpups, of which there were not many, could do this, but they didn't improve the idle quality of hi-performance cams. These lifters addressed that but also allowed the cam to idle lower, a benefit especially for automatic trans equipped vehicles.
You can go to the Rhodes website and find some articles on them or just google them and get more information. You can also give them a call and ask them questions about your application or for references. You could just google them and find other feedback. Here are just two...
http://www.jalopyjournal.com/forum/t...or-bad.454737/
http://www.nastyz28.com/forum/showthread.php?t=233029
Good luck... GUSTO