Roller lifters/cams VS. flat tappets

Not shooting the messenger....

j-rod said:
Again, I invite you to reread what I posted. I am not making these claims. Perhaps you guys should talk to a few Cummins engine and/or tractor engine builders since you seem to be "shooting the messenger" here.

And no, I am not confusing hydraulic and mechanical lifters. LOL
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I understand that you were told this, but if someone tells you it doesnt hurt to shoot yourself in the foot are you gonna try it? Here is what you have. Nobody is mass marketing a roller set-up for the Cummins, YET. FYI, they ARE out there, and it may surprise you to see who has them.:poke::evil. In almost all forms of racing valve train is the limiting factor. Just because it works at lower RPM doesnt mean its the best option. It may be your only option so far. There MIGHT even be a couple guys reading this and saying, SHUSH, dont let the cat out of the bag!!!! Have any of you guys changed a engine over to rollers from flat tappets and changed nothing else? Guess what! Upon starting the engine it is quite common to have to adjust the idle DOWN using the exact same carb you had before. Why? Less friction which frees up power. I honestly dont understand how anyone cam claim a flat tappet is better. It defies all logic AND physics.
 
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matty169 said:
400 lbs SEAT pressure DOES NOT AND CAN NOT happen on a flat tappet!!! EVER!!!! Thats even too much for a roller set-up. Pressure on the nose, well, thats different. Also, if you think your valve is controlled at 5000 rpm with those springs you are wrong. Guarantee you that it is lofted over the nose if the ramps are even REMOTELY fast. We even tried ceramic lifters with a flat tappet. Guess what, as soon as you loft it over the nose and the lifter comes back to earth shiiit goes WAY bad way fast. And ceramic going through the engine destroys EVERYTHING, EVERYTIME. $30-50K paper weight. Remember several years ago at the beginning of the Nascar season? 2 big engine builders were lucky to have 1 engine survive the race out of about 10. Needless to say, ceramic lifters didnt last long. LOL
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Those numbers are on an extreme engine, turning 10K, and who said it was a flat tappet?


I am still curious about the equation for kinetic energy.
You do know what the m and the v stand for right?
 
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OK.

zstroken said:
Those numbers are on an extreme engine, turning 10K, and who said it was a flat tappet?
Thats the whole point. You can run higher pressures with a roller cam so you CAN control the valve closing and opening, instead of lofting it over the nose.

I am still curious about the equation for kinetic energy.
You do know what the m and the v stand for right?
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Mass, velocity.
 
matty169 said:
I understand that you were told this, but if someone tells you it doesnt hurt to shoot yourself in the foot are you gonna try it? Here is what you have. Nobody is mass marketing a roller set-up for the Cummins, YET. FYI, they ARE out there, and it may surprise you to see who has them.:poke::evil. In almost all forms of racing valve train is the limiting factor. Just because it works at lower RPM doesnt mean its the best option. It may be your only option so far. There MIGHT even be a couple guys reading this and saying, SHUSH, dont let the cat out of the bag!!!! Have any of you guys changed a engine over to rollers from flat tappets and changed nothing else? Guess what! Upon starting the engine it is quite common to have to adjust the idle DOWN using the exact same carb you had before. Why? Less friction which frees up power. I honestly dont understand how anyone cam claim a flat tappet is better. It defies all logic AND physics.
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Did I say I believe it or am not going to consider running a roller camshaft? You guys read way too much into things.

Yes, I am aware of shops producing and installing roller cams for the Cummins, as I have talked to them already.
 
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matty169 said:
Mass, velocity.
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You do see that it is velocity^2 right?

back to the discussion of the mass and velocity aren't directly proportional. Something spinning 2 times the speed has 4 times the energy.
 
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Only if......

zstroken said:
You do see that it is velocity^2 right?

back to the discussion of the mass and velocity aren't directly proportional. Something spinning 2 times the speed has 4 times the energy.
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That is only if MASS is constant. Your heavy Cummins parts take more spring pressure to control. That was your question, correct? How much do stock style tappets weigh? Valves? Rockers?

If you cut down weight you can run more radical cam profiles with less seat pressure.
 
zstroken said:
One thing to remember is an engine that runs 9000 rpm needs a little more spring pressure than an engine that turns 4500 or so.
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zstroken said:
I understand that there are many things to consider, my point was just because the cummins stuff may weigh 2 times as much but travels at half the speed, doesn't mean it needs the same spring rates.
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matty169 said:
That is only if MASS is constant. Your heavy Cummins parts take more spring pressure to control. That was your question, correct? How much do stock style tappets weigh? Valves? Rockers?

If you cut down weight you can run more radical cam profiles with less seat pressure.
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I never said mass was held constant, the first line I quoted is what I said.
 
Chris Tobin said:
Matty already made the point I was trying to make... Roller will be better than flat tappet every time. I do not see any case where you can show that a flat tappet would make more power than a roller cam... It just doesn't make sense!!! Maybe you are confusing hydraulic vs mechanical lifters... in those cases the non hydraulic will make more power but there is also more maintenance and for street engines most builders recommend staying with hydraulic lifters, with roller hydraulic being the best for street engines...
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most automotive flat tappet applications don't have a large mushroom headed lifter... makes a huge difference at the valve
 
Forrest Nearing said:
most automotive flat tappet applications don't have a large mushroom headed lifter... makes a huge difference at the valve
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BINGO!!!!! Now, if you're comparing same diameter flat tappet to same diameter roller I like the roller every time! Mushroom lifters don't have an equivalent diameter roller generally speaking save for maybe something like top fuel and even then I still think mushroom lifters have more surface area.
 
Did anyone ever consider utilizing and/or fabricating a side-loading, bolt in cam follower style like a nt or k series cummins?


ediT: ....just sayin'......
 
KILLER 'B' said:
Did anyone ever consider utilizing and/or fabricating a side-loading, bolt in cam follower style like a nt or k series cummins?


ediT: ....just sayin'......
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You dont have access to the cam through the tapper cover. But cool idea.
 
ok i have yet to see a roller lifter for a cummins what are yall using and can they be streetable?
 
One would think that a roller cam would make more power (less friction, More aggressive cam profiles, etc) But when I spoke to Van Haisley last year he told me they can actually make more power with a flat tappet cam. He didn't elaborate. So I cant tell you why.
 
You get more power from a mushroom flat tappet vs a roller cam because the diameter of the lifter limits the maximum speed of the ramp possible with a roller cam, whereas a mushroom tappet allows a much faster more aggressive profile, therefore giving more area under the curve. The nascar boys have this science down to an art, and even if they were allowed to run rollers would not change over in any research posted online

Now if you are discussin the standard flat tappet lifter vs a roller lifter of the same diameter, the roller wins every time for more power production, and not because of the reduced friction elements

This has been discussed to death here several times.
 
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