what are the advantages, if any, of roller lifters and rockers for a driver type hot rod for the street?
Roller lifters allow more aggressive valve opening rates. More airflow/more power without excessive duration. Good power without sacrificing drivability or economy.
oh yeah and with a roller cam shaft the profiles can be mch more agressive with out wearing the cam out de to the lobe ramp and same with duration, lift etc....
It also depends on whether you are referring to hydraulic roller cams, or solid roller cams....and what particular engine family you are referring to....the projected mileage per year...what kind of performance you expect...and your budget.
engine family is sbc(350) and I ***umed from my builder that we were talking hydraulic...mileage, couple grand, and I was expecting quick smooth operation..and money is an issue but not a huge one. I was just looking for a little more quality and like the other dewds said, less friction.
OK. My take on things is that for the SBC, the hydraulic rollers are a pretty good deal...lots of choices, (sort of) reasonable prices, and easy to set up, especially if you have a late roller block anyway. Solid rollers on the street...a whole 'nother deal. The SBC is kind of the "poster child" for hydraulic roller cams. There are certain engine families that I would think very long & hard about using a hydraulic roller, the BBF coming to mind...the geometry takes a great deal of work to fix. So far as rocker arms, if nothing else I'd use the Comp Magnums with the roller tip for even very mild engines. The only other thing I'd add is to stay away from cheap rockers, whether the stamped kind or full roller rockers....trouble waiting to happen. Harland Sharp & Scorpion are two brands that are reasonable in price & will stay together. All the major cam companies have decent roller rockers that will work fime for a street engine.
A quick look at Summit Racing shows complete hydraulic roller cam kit (a "K-" kit) at $969. A hydraulic flat tappet K-kit runs $329.95. You'd be money ahead if you spent the 600 dollar difference on a decent set of aftermarket heads. The best bang for the buck a****st the cam type choices is a solid flat tappet cam kit at $452 but you've got to adjust them and they can be 'vocal' at times. A solid roller will make the most power - bar none.....the solid roller K-kit runs $887 but when running solid rollers on the street you really need to step up to Endur-X roller lifters which run 534 dollars. Ouch. Bottom line....if you want quiet, smooth operation then I would ***ume your not necessarily looking for every last horsepower the motor can make. Under that ***umption your best money is spent on good quality internal components, get the rotating ***embly professionally balanced and buy some decent aftermarket heads that are set up correctly for the camshaft your using. A roller cam does not always equate to "quality". There are some definite advantages to a roller cam, don't get me wrong. BUT when your balancing budget vs HP vs smooth operation and driveability the extra money spent on a roller cam comes in a distant third behind expertly executed meticulous ***embly and a good set of heads. -Bigchief.
There's a little good, and a little bad in everything. Roller lifters are great for a BIG cam in the solid function. In either solid or hydraulic they reduce friction...and allow for a larger profile. On the downside, roller lifters have to be kept in place to keep the roller in the right direction for rotation. That creates another mechanical situation. Add this to the already present mechanical situation due to them being a roller (bearings & wheels), and you have that many more chances for a failure. I just had a roller lifter go bad in my car, and was VERY fortunate to find it before it really made a mess. It's the basis of mechanical things...the more moving parts, the more chance for failure.
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