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Originally Posted by tony xa
Just looked into the price of roller cam and roller lifters .
the roller cam isn't to badly priced but the roller lifters are very exspensive
Does anyone know if you have to use roller lifters with roller cams and what is the difference is between roller cam, hyd roller cam and solid roller cam.
I am hoping you don't need roller lifters as they are way out of my price range.
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Another voice chiming in with MUST use roller lifters with roller cams. Roller cam lobes are usually very aggressive and "steep." What it means is that because of the roller tip of the roller lifter being able to track the lobe of the camshaft when the lobe is cut at a sharper angle than could be cut with a flat (hydraulic or solid) tappet, the roller lobe shape is usually a much sharper angle. Sharper angles mean that the time period between valve lift starting and valve completely lifted is much shorter with rollers than with flats. What this means is that the valve is opened more fully sooner. The cam grinder does not need to make the cam any more or less "wild" with a roller, but it certainly does mean that the cam grinder CAN make the cam much more wild because of the ability to get the valves up to full lift more quickly, hold them open much longer and then pretty much slam them back down on the back side all because the rollers are able to track a sharper cut lobe.
We've all seen tire commercials where they show the tire "contact patch" with the road during rainy nights with mum and 5 kids in a caravan trying to get home safe at night after a football match. "You've got a lot riding on those tires" kind of stuff. The same is basically true for a roller lifter, except that it doesn't flatten out to the "road" the way a tire does, rather it maintains a very thin line of contact on the face of the lobe. Because of the radius of the bearing tip, the lifter sharply angles away from the lobe face after only a very small distance compared to flat tappets. Flat tappets have a convex surface to their faces. That is, they are actually curved outward a slight bit. Try standing a lifter upright on a piece of glass or other smooth, flat surface. It will wobble about. This is the convex face. The "contact patch" for this style of lifter is much more similar to the tire on the road because a broader area is in contact with the lobe. Also, the lobe angle can not be so sharp as to come into contact with the outside edge of the lifter and the concaveness of it is very moderate compared to the sharpness of the roller tip lifter.
Flat tappet camshaft lobes tend to look more egg shaped while roller cam lobes tend to look more like an "oval track" with both sides of the oval being very tall and sharp and with long "straight aways" in the middle.
Here are photos that illustrate the differences in lobes:
We start with typical flat tappet lobe, move to a hydraulic roller and finish up with a solid roller lobe.
Here is a shot of the lobes overlapping each other for each of the three lobes shown in the photos. To illustrate the "sharpness" of the lobes made possible by the lifter types, look at the point in (time) angles of camshaft movement where each obtained .300" tappet lift. The hydraulic flat started at about 112* and ended up obtaining the .300" tappet lift by 180* for a difference of 68* of camshaft movement. The hdyro roller started at about 106* and obtained it by about 160* for a difference of 54*. The solid roller started at about 85* and obtained it by about 135* for a difference of 50*.
68 = hydraulic flat
54 = hydraulic roller
50 = solid roller
What this tells us is that the lobes are steeper (less time to ascend to the same distance upward) based on the type of tappet used, but also because the properties of the kind of tappet used allow cam designers to be more "wild" with their roller cams.
We also need to step back for just a second and talk a bit about time. Time in an engine is extremely important and one of the first things we measure in the form of RPM. How many guys add a tachometer to an otherwise no-tach car? Doesn't every race car you ever see have a big ol' tach sitting in/on it somewhere? ...right in the driver's view? We know that the camshaft turns at half the speed of the crankshaft or that the crankshaft turns twice for every one camshaft revolution. If it takes 68* in camshaft movement to raise the lifter to .300", it takes us twice as long in crankshaft time or 136* of crankshaft movement.
136* HF
108* HR
100* SR
It sure looks like a lot bigger difference when you compare the time to how far the crank turns before the lifter is lifted to the .300" point.
If we focus on the timing "capability" of using a SR or HR over that of a HF, we can build the same HF type cam using a roller and open the valves at a time earlier or later (depending on what we want the cam to do) in crankshaft movement for the same total lift and duration. What this means is that for the same valve timing events, we can reach maximum lift in fewer degrees of rotation and therefore be at maximum lift for a longer period of time than with a HF type lobe. This makes the camshaft no more or less wild, but improves power because we're at maximum lift soon, which helps flow in and out. It does play hell on valve springs and budgets, but it gives us the ability to more precisely (in time needed to obtain some lift value) control our valves.
Of course, most people who spend the money on a roller camshaft, lifters and increased rate springs also tend to go for "more" cam that approaches the wild side, which is why those cams are "stocking" parts versus custom grinds.
My word of advice is never, never, never mix and match camshaft and lifters. Use the recommended lifters for the cam. Don't use/buy a new cam and use it with used lifters or vice versa. Don't mix used lifters to different lobes when reinstalling a cam. Some people do it and seem to run just fine on it, but I don't recommend it.
I only use solid roller cams and the above commentary should tell you why. Very tight control over valve events...at least as tight as current technology enables for pushrod engines. I would certainly consider using a hydraulic roller for a pure street car, or even a hydraulic flat tappet for a budget-minded engine. There is nothing wrong with them. They've been working for years and some guys will tell you that you can make just as much power with a solid flat tappet cam as you can make with a solid roller tappet cam for a 351C. This is usually because the build of the engine does not warrant a really seriously aggressive profile cam, like the SR shown in the earlier photo. Most of us are not planning on using .822" valve lift (.475" lobe lift with a 1.73:1 rocker arm) or even more that is possible using really aggressive roller cams. A 12.5:1 stock stroke .030" over Clevo can only use so much cam and both solid flat and solid roller can fulfill that requirement. However, as I regularly prove, I can build more total power using a SR than can a guy using a SF because of the precision timing events possible from a roller camshaft.
For the money, I'd buy a SR over a HR simply because you can spin a SR a lot higher than a HR and you pay the same price for each of them. However, I am different than others, so what meets my needs are not as likely to meet someone else's needs, either for budget or build. It is true that most of the SR cams that you can buy are way too much cam for a typical street engine that sees a lot of driving time. A HR or flat tappet cam is just fine for those applications. Unfortunately, I don't have a street car like that to put such a cam into.
If you want the benefits of a roller cam, save up for the lifters and take a bit longer to complete your engine. A roller cam makes all the difference in the world and they do not usually require a break-in period the way flat tappet cams do. But most require a bronze distributor gear. There is always a pro and a con side with everything. For hot, true street performance, a flat tappet cam either hydraulic or solid is just fine.
:davis:
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