Scooter's Roofing
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what's the OD of the lifter bodies?
Roller lifters/cams VS. flat tappets
- Thread starter matty169
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what's the OD of the lifter bodies?
??????
One proven way to increase power is by decreasing the amount of valvetrain friction. The biggest friction hot spots in any valvetrain are those where the lifter comes in contact with the cam lobe, where the rocker fulcrum rides on the shaft or stud, and where the tip of the rocker comes in contact with the valve stem. In basic, simplified terms, the more energy your engine exerts by overcoming these high-friction contact points, the less torque is exerted to the rear wheels. Replace the rubbing metal-to-metal contact with a bearing of some type, and the engine is going to spend less energy doing the same work. Hence, the creation of roller lifters and roller-tipped rockers.
With roller cams, two benefits are noted: (1) the friction reduction of a roller lifter and (2) the radical cam profiles the roller allows. Even if total lift is the same, the higher velocities are possible with a roller tappet lifter as opposed to a flat tappet lifter. The roller lifter’s higher velo-city is the key to achieving higher lifts sooner in the lift curve. While acceleration is quicker with a flat tappet, the velocity of the flat tappet lifter is limited by the lifter’s diameter.
While most will assume that the only benefit of roller rockers is reduction in friction, the other benefits of aftermarket roller rockers include true, blueprinted, at-the-valve ratios and precision motion.
By placing a roller on the tip of the rocker where it comes in contact with the valve stem, the rocker is able to roll across the valve as it travels through its cycle, instead of sliding back and forth across the valve stem. Beside the obvious friction created here by non-roller tips, serious side loads are placed on the valve stem as the tip drags across the top of it while the valve travels up and down in the valve guide, contributing to worn guides (Fig. 1).
I understand that in this application(Cummins) a mushroom lifter is easiest and works well and the 1.5" mushroom helps with velocity, but if you can make a roller lifter fit it will perform better, and you DONT need a lifter body as large as a mushroom lifter either.
As for 07dodge and this comment, "If you run too steep of ramp angle on a roller cam, you are gonna have lifters outside your block!" Go back and read some cam specs I posted earlier. Yes, it is a fuel bike cam. No it is not diesel. It doesnt matter. Its a matter of mechanical properties and what will or wont work. If anyone on here can read cam specs, draw a picture of that cam profile and then try to tell me your steep ramp angle theory and the results of running one holds up. That cam has ramps faster than ANYTHING you have ever seen. The lobe at peak lift is nearly wider than the base circle. It holds the valve at peak lift for a full 35 degrees of crank rotation before starting to close the valve. It wouldnt be possible with ANY flat tappet lifter.
Who sells a roller cam set-up for a 24V? Thanks
I have no idea. I just found it and thought it was interesting. Here is an article from Crane Cams.
One proven way to increase power is by decreasing the amount of valvetrain friction. The biggest friction hot spots in any valvetrain are those where the lifter comes in contact with the cam lobe, where the rocker fulcrum rides on the shaft or stud, and where the tip of the rocker comes in contact with the valve stem. In basic, simplified terms, the more energy your engine exerts by overcoming these high-friction contact points, the less torque is exerted to the rear wheels. Replace the rubbing metal-to-metal contact with a bearing of some type, and the engine is going to spend less energy doing the same work. Hence, the creation of roller lifters and roller-tipped rockers.
With roller cams, two benefits are noted: (1) the friction reduction of a roller lifter and (2) the radical cam profiles the roller allows. Even if total lift is the same, the higher velocities are possible with a roller tappet lifter as opposed to a flat tappet lifter. The roller lifter’s higher velo-city is the key to achieving higher lifts sooner in the lift curve. While acceleration is quicker with a flat tappet, the velocity of the flat tappet lifter is limited by the lifter’s diameter.
While most will assume that the only benefit of roller rockers is reduction in friction, the other benefits of aftermarket roller rockers include true, blueprinted, at-the-valve ratios and precision motion.
By placing a roller on the tip of the rocker where it comes in contact with the valve stem, the rocker is able to roll across the valve as it travels through its cycle, instead of sliding back and forth across the valve stem. Beside the obvious friction created here by non-roller tips, serious side loads are placed on the valve stem as the tip drags across the top of it while the valve travels up and down in the valve guide, contributing to worn guides (Fig. 1).
I understand that in this application(Cummins) a mushroom lifter is easiest and works well and the 1.5" mushroom helps with velocity, but if you can make a roller lifter fit it will perform better, and you DONT need a lifter body as large as a mushroom lifter either.
As for 07dodge and this comment, "If you run too steep of ramp angle on a roller cam, you are gonna have lifters outside your block!" Go back and read some cam specs I posted earlier. Yes, it is a fuel bike cam. No it is not diesel. It doesnt matter. Its a matter of mechanical properties and what will or wont work. If anyone on here can read cam specs, draw a picture of that cam profile and then try to tell me your steep ramp angle theory and the results of running one holds up. That cam has ramps faster than ANYTHING you have ever seen. The lobe at peak lift is nearly wider than the base circle. It holds the valve at peak lift for a full 35 degrees of crank rotation before starting to close the valve. It wouldnt be possible with ANY flat tappet lifter.
Who sells a roller cam set-up for a 24V? Thanks
Here is yet another cam maker and what they say.
Flat Tappet Cams vs. Roller Cams - Lunati Power
See where it says "inverted"? Do some of you know what that means? Can you do it with a flat tappet?
Flat Tappet Cams vs. Roller Cams - Lunati Power
See where it says "inverted"? Do some of you know what that means? Can you do it with a flat tappet?
This is the best I can do for you.
FLAT VS ROLLER TAPPET TEST
We know someone is going to ask for it, so now we'll explain why this really doesn't make any sense. We're talking about a dyno test between a flat-tappet cam and a roller cam with the same specs. The reason it wouldn't work is because even if the numbers @ 0.050 were equal; the cams can never actually be the same. Roller lobes are designed to open the valves with much more "area under the curve". That means that as the valve approaches max lift, a roller tappet can hold it open longer than a flat tappet. A roller vs. flat tappet test could never be equal no matter how the cams were ground. If we were to cut a roller lobe that EXACTLY matches the profile of a flat-tappet lobe, or even if we put a roller tappet on a flat tappet cam, the test results would still show the roller ahead, albeit slightly, simply as a result of less friction. But, there'd never be a reason for that type of lobe, or test, because it'd not be taking advantage of everything a roller tappet has to offer. However, we've done a few tests that closely mimic this idea and found interesting results. Certain flat tappet cams might be capable of more low-end power due to their slightly more aggressive initial opening rates. But their advantage quickly goes away as frictional losses start to take over compared to roller tappets and the top-end power increases of the roller tappets far outweigh the marginal low-end advantage.
This was a magazine article from a cam company. It also included this.
IT STARTS WITH THE CAM
There's actually way more to camshafts then we could ever explain in just a few pages, so we'll hit on the hard points of cam selection and offer up some data to support our theories. First of all, keep in mind that the cam's lobes are designed to do only one thing: push the lifter, (a.k.a. tappet), smoothly up to open the valve and let it follow the lobe back down to close the valve without bouncing it off the seat. It's much more difficult than you might think. Good-old flat tappet cams have never been the most efficient way to do this, but they were cheap. And their low cost has kept them popular. But now, flat tappets are becoming increasingly harder to find and their prices keep going up. There are a lot of reasons for this, not the least of which is that flat tappets actually cost horsepower. Another is that the OEM's haven't put a flat tappet cam in their engines for almost 20 years. So why should you? If it were still a good way to do things, the cost-conscious OEM's would've stuck with flat tappets forever. So where did the big push for rollers come from? That's easy to answer. It was all about reducing friction. Because friction costs power and since they're always looking to make the most reliable power for less dough, the OEMs choose to reduce friction inside the engine first. But notice that they've only advanced to hydraulic roller tappets yet.
FLAT VS ROLLER TAPPET TEST
We know someone is going to ask for it, so now we'll explain why this really doesn't make any sense. We're talking about a dyno test between a flat-tappet cam and a roller cam with the same specs. The reason it wouldn't work is because even if the numbers @ 0.050 were equal; the cams can never actually be the same. Roller lobes are designed to open the valves with much more "area under the curve". That means that as the valve approaches max lift, a roller tappet can hold it open longer than a flat tappet. A roller vs. flat tappet test could never be equal no matter how the cams were ground. If we were to cut a roller lobe that EXACTLY matches the profile of a flat-tappet lobe, or even if we put a roller tappet on a flat tappet cam, the test results would still show the roller ahead, albeit slightly, simply as a result of less friction. But, there'd never be a reason for that type of lobe, or test, because it'd not be taking advantage of everything a roller tappet has to offer. However, we've done a few tests that closely mimic this idea and found interesting results. Certain flat tappet cams might be capable of more low-end power due to their slightly more aggressive initial opening rates. But their advantage quickly goes away as frictional losses start to take over compared to roller tappets and the top-end power increases of the roller tappets far outweigh the marginal low-end advantage.
This was a magazine article from a cam company. It also included this.
IT STARTS WITH THE CAM
There's actually way more to camshafts then we could ever explain in just a few pages, so we'll hit on the hard points of cam selection and offer up some data to support our theories. First of all, keep in mind that the cam's lobes are designed to do only one thing: push the lifter, (a.k.a. tappet), smoothly up to open the valve and let it follow the lobe back down to close the valve without bouncing it off the seat. It's much more difficult than you might think. Good-old flat tappet cams have never been the most efficient way to do this, but they were cheap. And their low cost has kept them popular. But now, flat tappets are becoming increasingly harder to find and their prices keep going up. There are a lot of reasons for this, not the least of which is that flat tappets actually cost horsepower. Another is that the OEM's haven't put a flat tappet cam in their engines for almost 20 years. So why should you? If it were still a good way to do things, the cost-conscious OEM's would've stuck with flat tappets forever. So where did the big push for rollers come from? That's easy to answer. It was all about reducing friction. Because friction costs power and since they're always looking to make the most reliable power for less dough, the OEMs choose to reduce friction inside the engine first. But notice that they've only advanced to hydraulic roller tappets yet.
07dodge
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NickTF
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For all practical purposes it simply comes down to the following: For practical purposes compare a roller lifter which will fit a stock cummins lifter bore or typical sizes the cummins block lifter bores can be machine to without running into issues with the oil gallery or other possible issues to a typical cummins mushroom lifter. Plot acceleration of the valves by mapping lift vs. crank rotation (as Zach and possibly others have stated) for identical @ 0.050" duration cams, one roller an one flat tappet mushroom, and the discussion ends after comparisons are made. For the ultimate in determining the effects of mushroom vs. roller lifter all duration numbers as measured at the lobe (.006", .050", .100", .200", .300" etc.) should be kept the same but this neglects taking advantage of what each lifter platform offers.
Nearly all flat tappet vs. roller discussions are concerning normal non mushroom diameters between .842 an 1", the cummins doest not fall into this category when measuring the face of the mushroom lifter so far as my tiny brain understands.
The above test will not take into consideration any stability issues at rpm which may be present with each platform but it's a good start to end this debate atleast when discussiong lift profile transfered to the valve.
Nearly all flat tappet vs. roller discussions are concerning normal non mushroom diameters between .842 an 1", the cummins doest not fall into this category when measuring the face of the mushroom lifter so far as my tiny brain understands.
The above test will not take into consideration any stability issues at rpm which may be present with each platform but it's a good start to end this debate atleast when discussiong lift profile transfered to the valve.
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Thanks.........
Thanks, and I understand all that. My point was that for MAX performance and quite possibly longevity(especially with max performance cam profiles) a roller lifter is a good idea for several reasons. I never said anything about using the stock size lifter bore, and to be honest, I dont know how big a bore is possible with machining or what the options are in a Cummins. I am looking at this from the standpoint that if you build an ALLOUT flat tappet engine and an ALLOUT roller engine, the roller wins. If you compare 2 engines that are similar builds(even street engines) a roller cam will ALMOST ALWAYS perform better(although packaging in a Cummins appears to be an issue). I never said anything bad about Hamiltons products to my knowledge. I had considered using his cam to replace my Helix 2 and compare them on the dyno. I had p.m.d him a couple months back about it actually and his recommendations for a cam for my truck. I am going to look into a roller set-up, but so far I havent found one for a 24V. Scheid does use them in his big pulling builds I guess, but they arent 24 Valves.
Something else Hamilton said that I wanted to address was the issue of side loading and higher oil temps with a roller cam because of the roller lifters. I dont know who told him that, but I havent seen that and we actually run some cams that have an inverted lobe. This profile would create the most side loading possible on the lifter and its bore. We have NEVER had a lifter failure and our lifters have absolutely NO oil going to them or the lifter bore.(yes this is a bike, doesnt matter) I decided I would check to see if I was missing something so I contacted Crane, Comp, Bullet/Ultradyne, and Howards cams along with DEI and Childress racing engines.(places we order from) They all told me I was confused, unless you were running WAY too much spring pressure for the application. Maybe its possible, who knows.
To those of you thinking maybe I dont know anything, heres an idea of what you can do if you think outside the box. We raced in a class where everyone else runs 160-180" billet engines. We ran Delkron(street bike) cases and a 124" engine. They run 13" slicks, we run 11". They ran high 5 second, low 6 second quarter miles, we ran low 6 seconds. They ran a 2 or 3 speed trans, we ran 1 speed. They break alot, we dont.
Just because its not what everyone else does doesnt mean it wont work. We do circle track, asphalt, dirt and off road engines. We are never lacking horse power, although its always nice to have more.
Thanks, and I understand all that. My point was that for MAX performance and quite possibly longevity(especially with max performance cam profiles) a roller lifter is a good idea for several reasons. I never said anything about using the stock size lifter bore, and to be honest, I dont know how big a bore is possible with machining or what the options are in a Cummins. I am looking at this from the standpoint that if you build an ALLOUT flat tappet engine and an ALLOUT roller engine, the roller wins. If you compare 2 engines that are similar builds(even street engines) a roller cam will ALMOST ALWAYS perform better(although packaging in a Cummins appears to be an issue). I never said anything bad about Hamiltons products to my knowledge. I had considered using his cam to replace my Helix 2 and compare them on the dyno. I had p.m.d him a couple months back about it actually and his recommendations for a cam for my truck. I am going to look into a roller set-up, but so far I havent found one for a 24V. Scheid does use them in his big pulling builds I guess, but they arent 24 Valves.
Something else Hamilton said that I wanted to address was the issue of side loading and higher oil temps with a roller cam because of the roller lifters. I dont know who told him that, but I havent seen that and we actually run some cams that have an inverted lobe. This profile would create the most side loading possible on the lifter and its bore. We have NEVER had a lifter failure and our lifters have absolutely NO oil going to them or the lifter bore.(yes this is a bike, doesnt matter) I decided I would check to see if I was missing something so I contacted Crane, Comp, Bullet/Ultradyne, and Howards cams along with DEI and Childress racing engines.(places we order from) They all told me I was confused, unless you were running WAY too much spring pressure for the application. Maybe its possible, who knows.
To those of you thinking maybe I dont know anything, heres an idea of what you can do if you think outside the box. We raced in a class where everyone else runs 160-180" billet engines. We ran Delkron(street bike) cases and a 124" engine. They run 13" slicks, we run 11". They ran high 5 second, low 6 second quarter miles, we ran low 6 seconds. They ran a 2 or 3 speed trans, we ran 1 speed. They break alot, we dont.
Just because its not what everyone else does doesnt mean it wont work. We do circle track, asphalt, dirt and off road engines. We are never lacking horse power, although its always nice to have more.
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NickTF
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I wasn't just addressing this reply only at you but the thread and this subject in entirety. As others have said this isn't the first time it's come up. Again, i'm not sure about the longevity comment either when comparing a mushroom lifter with a bigger face diameter to a roller lifter. If we were talking same diameter non-mushroom lifters however I would agree roller is likely to offer durability advantages but that huge face of the mushroom probably makes life pretty easy given the lifter edge does not dig into the lobe like in traditional ~.842ish sized flat tappet applications. Don't forget roller lifters (most) have a shaft and some form of retaining mechanism to fail vs. the big mushroom lifter being a solid piece.
Side loading may or may not be an issue depending on length of the lifter and the lifter bore. Do you know for certain that your bike example has the same length lifter body and bore as a cummins? Otherwise it's apples to oranges.
No one is questioning your credentials, that's not what this thread is about so no need for further examples of your accomplishments unless they are directly relevant to the discussion at hand, which is quite a good one.
05_LLY
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That is something i often wondered about but never asked even with the crazy boost some of us run, running 1/2 to 2/3 the amount of rpm as a gasser and run a 1/4 of the seat pressure the gasser guys run? My thoughs always beena (example)~ 60psi of boost, 110lbs spring on roughly 1"surface area" valve leaves about 50lb of pressure to get a rather heavy retainer, keeper, and valve closed befor the piston closes it for ya? Sorry if i make no sense.....ill sit back and listen now!! Thanx
Our junk.....
Yes, most rollers have tie bars. Ours dont. We use a groove and a lifter with a pin that rides in that groove. It serves more than one purpose.
I dont know the diameter or length of Cummins lifters, or more importantly to me, what diameter is possible to machine the bore to. Diameter is .842 on ours I believe. Length is about the same as a small block chevy. FYI, the longer the lifter and shorter the pushrod stabilizes the valve train at higher r.p.m.s, but you have to watch all the related geometry/angles of valve stem, pushrods, rockers, etc. Thanks
Yes, most rollers have tie bars. Ours dont. We use a groove and a lifter with a pin that rides in that groove. It serves more than one purpose.
I dont know the diameter or length of Cummins lifters, or more importantly to me, what diameter is possible to machine the bore to. Diameter is .842 on ours I believe. Length is about the same as a small block chevy. FYI, the longer the lifter and shorter the pushrod stabilizes the valve train at higher r.p.m.s, but you have to watch all the related geometry/angles of valve stem, pushrods, rockers, etc. Thanks